The ProMaster Second Alternator Skid Plate – Version 3

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If you’ve been around here a while, you probably remember my last post on the skid plate to protect our ProMaster’s second alternator.  But just in case you haven’t, let me bring you up to speed.

A number of ProMaster based RVs have a second alternator installed as part of their electrical system.  Besides our own Travato – which is a bit special – the second alternator can be found in the Roadtrek Zion and the Hymer Aktiv.  This second alternator rides pretty low to the ground, and when you see it, you’ll be a bit concerned about whacking it into a “retread snake” along the interstate.  Leaving the alternator exposed, or using a flimsy plastic cover on it weren’t options for me.  So we partnered with EDGE Motorworks, in California, to develop a way to protect this vulnerable alternator.  After two iterations, the alternator skid plate looked like this:

This was version 2.  Version 1 was a steampunk looking affair.

Before we go any further, I’d like to acknowledge that what we’re developing here might not fit everyone’s definition of a “skid plate”.  I would not – as one commenter suggested – attempt to jack up the RV by this tray, for example.  Depending on your point of view, you might see this as an “undertray”, a “guard”, or a “shield”.  And those might be more appropriate terms around the garage.  But this is an RV website, and not an off-roading one.  So while I respect the difference in terminology, I plan to continue using all of the terms more or less interchangeably.  I think we all know what I’m referring to.


Now, that last version was a solid attempt, and it stayed in place on Lance through a couple months of testing with no failures, and never so much as a rattle.  But we knew we could do better.  Right away, after installing this skid plate, we identified three areas where where could improve:

  1. Thicker Material. This skid plate was made out of 16 gauge steel.  We wanted to do better, and work in 1/8″ thick steel.
  2. Better Mounting. Rather than tapping into sheet metal, we wanted a more solid mounting point.  We wanted to bolt on to the frame rails.
  3. Angles.  We wanted to angle and curve the front of the skid plate to present a glancing surface to obstacles.

So, after two or three months of testing, it was time to head back to EDGE Motorsports for the next iteration of the skid plate. Once again, Stef didn’t come along, and she’s probably really glad, because Lance spent most of the week inoperable and ugly in the parking lot.

Stay classy, Lance.

But in the end, I’m happy to report the new fitment went well, and now I feel more like I’m driving a tank.

Mad Lance

You’ll notice there that we’ve swapped out Lance’s nose ring for more of a full face mask.  I’m not sure if I dig the black color yet, and we may be changing that at some point.  The reason we did this was simple.  We wanted to have a look at something that securely attached to the frame, so we could base our skid plate mounting off that.  This grill guard attached to the frame, so we got one to study.  As a result, the new skid plate attaches to the frame, and will work either with or without this grill guard.  When all was said and done, we had the grill guard sitting around, so why not mount it?!

This skid plate is only falling off if the whole bumper falls off.

This mounting scheme addresses the second of our areas for improvement.  Whereas the first version of the skid plate was installed with self-tapping screws into sheet metal.  This thing is bolted onto the frame with bolts that I can’t torque the heads off of.  (I have a really bad habit of torquing the heads right off of bolts.  This probably has more to do with the fact that I buy lots of cheap Chinese bolts than it does with my strength…)

Apart from the “Mad Max” grill guard, the improvements to the skid plate are substantial.  Addressing the first of our areas for improvement, this thing is over seventy pounds of thick (.125″) steel.

So beefy, it was a pain in the a** to move around!

You’ll notice that this one is considerably bigger than version 1.  We reasoned, if we’re going to protect things underneath the rig, why not go all the way.  This new skid plate protects the oil pan, the pan underneath the transmission, and pretty much anything else you can see in this picture.

The seamy underbelly of a ProMaster…

This meant, of course, that we had to cut a hole in it to allow access for changing the oil without removing the whole affair (because removing it is pretty difficult).

We could’ve cut the hole a hundred yards wide, and the guys who change my oil would still find a way to make a mess of things.

The size and weight of the skid plate meant it took two of us to install it properly.

Don’t be fooled by the alignment rack.  I’m actually holding up the entire rig here.

Once we got it up, we were able to get a good look at the clearance picture to the second alternator.  We felt like this was adequate clearance to all belts, hoses, and electrical parts.

Plenty of space in there.

You’ll notice the slick curve under the second alternator.  This, and the angled front of the rest of the skid plate addressed our third area for improvement.  But fashioning this curve was a bit difficult, and required lots of gratuitous welding and sparks to get it just right (it only took us two attempts).

I checked it out. It’s actually an OSHA regulation that all welding gloves, jackets, and helmets have to have flames on them.

So now, with everything mounted, up, it sort of looks like this:

I WANT to run over things now…

And with that, it was time to leave EDGE and head for home.  On the way back, I stopped at a Starbucks.  When I got out, I happened to snap this picture of the underside of the rig as I had rolled up to the curb.  If anyone wonders why I’m eager to have something protect the second alternator, this picture pretty much explains it.  Without a skid plate, this curb would have hit it.

This makes me uncomfortable to look at.

So – Let’s Hear It!

And now we’re throwing this open to our readers.  We feel like the design of this thing has progressed enough to where we could entertain a few early adopters.  We can actually produce these things either with or without the bubble to protect the second alternator, so our audience is a bit wider than just those with the second alternator.  Our ideal early adopter would:

  • Reside close to the Mountain View, CA location of EDGE Motorworks
  • Have a Roadtrek or Hymer ProMaster-based rig with the second alternator installed
  • Or, have any ProMaster where protection of the undercarriage is desired
  • Be patient and understanding as we work to progress this further

If this sounds like you, please sound off in the comments below.  Do include your email (the emails are not published, only I will see them), and let us know if it’s OK to contact you about this.

And now, I’m off to go rock crawling in my Travato!  (just kidding)


James is a former rocket scientist, a USA Cycling coach, and lifelong fitness buff. When he's not driving the RV, or modifying the RV (or - that one time - doing both at once), you can find him racing bicycles, or building furniture, or making music. In his spare time, he works for a large IT company.

    55 thoughts on “The ProMaster Second Alternator Skid Plate – Version 3

    1. Humberto Gonzalez

      I have a 2018 Roadtrek on a 2017 Promaster Chassis. It came with a plastic guard on my second alternator (Generator Underhood.)

      Needless to say the plastic guard broke off and I’m interested in replacing with something stronger. My email is;
      _removed for privacy_
      Text message is best @
      _revoved for privacy_
      we talking about?

    2. Scott Farrell

      Hello – I couldn’t decide whether to ask this question here or in the ground clearance entry. Anyway, I know the ProMaster is not intended for off-roading. But there’s bound to be a time or circumstance when you start on a path that turns out to be more than expected. My question: Do you stick to pavement only, maintained dirt roads, gravel, or what? I saw a Travato somewhere that has all-terrain tires mounted, presumably for increased traction on dirt roads. Where is your line? Thanks!

      1. James - Post author

        Fair question.
        Maintained roads are all in-bounds for us. We will take almost any Forest Service road – dirt, gravel, what have you. But having said that, we always reserve the right to turn around if it gets too rough.

      2. Frank Strauss

        Hey there! I know this article is a little older but I hope the skid plate is still available! We have a 2021 Roadtrek Play with the second alternator and are in dire need of some protection!

    3. Jeffrey Pfefferle

      Hi James, we are interested in finding out the cost as well (for the under-hood skid plate and the zombie apocalypse front end protection … as well as installation). Would need to drive it to Gordon for install. THANK YOU, James and Gordon! Feel free to contact me (I am looking forward to it)!

      1. James - Post author

        You’ll have to call Gordon at Edge Motorworks to get the latest pricing and install timelines.
        (925) 803-8080

    4. Jason Keyser

      Now that it has been a couple years is it still working well? Do you know if EDGE Motorworks still does these? Is there a ballpark amount for this and the brush Guard? I have a 2018 Carado Banff with the underhood generator and it came with a plastic shield, but the rivets on the shield are too close to the rear wiring harness on the alternator and it rubs. For other owners this has eventually caused a short. I want to fix it before that happens. I don’t live in California but could make for a nice vacation trip.

      1. James - Post author

        Fair questions.
        The skid plate has held up wonderfully over the time I’ve had the final version installed. No issues whatsoever, and there’s plenty of room for cabling, etc without impinging on any wires.
        Gordon is still fitting and selling them, though I don’t have a good number to give you for a price.
        You can give him a call at Edge Motorworks in Dublin, CA and he’ll be able to give you all the details.

    5. Doug G

      Hi James, We hit a bag of seeds on highway 10 in Texas ripping off all but one of the bolts used to attach the plastic skid plate on our Hymer Aktiv. We live in Cupertino and will definitely be in the market for a new skid plate. Won’t be back in town until April though. How much would this cost?

      1. James - Post author

        I don’t know what Gordon is selling them for these days, but I’ll ask him to get in touch with you!

    6. Danielle Correia

      James, great stuff you and the Mrs have done here —
      we just purchased a 2018 Hymer Aktiv today….super excited!
      We are flying up from Long Beach to Oakland, to pick it up
      in Fresno this THURS! 19OCT… We were going to stay
      at a friends in Santa Cruz that nite, before making the drive
      home to Oceanside… We would LOVE a skid plate…
      is 5 biz days to short of notice for them to fab one up???

      1. Gordon White

        Hi, Gordon White here from EDGE Motorworks. Thursday or Friday works for me! Please call the shop at (925) 785-4477 and we can set it up.

    7. Roger

      My Zion arrived without a guard for the GU (2nd generator for my 400w lithiums). My understanding the initial designed cover caused overheating issues. A newly designed cover was installed in Jan. But I believe it is still plastic.

      1. James - Post author

        I’ve not had any overheating issues with ours.
        Of course, we’ve never sat on the blacktop in Arizona in the summer and idled to run the AC all day, either.
        (But in that scenario, our air conditioner couldn’t keep up anyway, so that’s all moot.)
        We left one side of the cover open. I’m hoping that would be sufficient. Though we always have the option to cut slots in it.

    8. Rick Markey

      I have been following your second alternator experience and all of the follow-ups. I don’t recall seeing any information about the effect of the second alternator on your fuel mileage, or on the performance of the Travato while on the road. That second alternator is a substantial additional load on the engine. My wife and I will most likely be purchasing a Travato later this year, and your reviews and all of the modification articles have been most helpful.

      1. James - Post author

        Hi Rick!
        The second alternator has resulted in no change whatsoever in fuel mileage or driving performance. In fact, we just had our best fuel-mileage-tank ever.
        The load from the second alternator is actually small. 180 amps at 12 volts is 2160 watts. That’s like 3 horsepower. The 300HP engine barely notices.
        The short answer is – don’t worry about it!

    9. Steve Day

      Hi James. Installing the second alternator in my 59G within a month. Not certain when I can make it Mountain View, but as I’m in Los Angeles, it’s not a big deal to get there. Definitely interested your protective plate solution. Also, I know you do not have a wiring diagram of your inverter/battery/alternator installation, but even an elementary napkin sketch would be helpful. just curious about how you connected your runs and in what order they went. Though I’ll be having knowledgable help with installing my system, I’d still love to see the wiring logic of your project. Thanks!

      1. James - Post author

        Hi Steve – I’ve passed your info on to Edge, and told them it was OK to contact you regarding a potential skid plate install. Let me know if you have trouble syncing up with them.
        As far as a wiring diagram – I’m going to have to pass there for several reasons. First – I’m not an electrician or an electrical engineer and I don’t wanto to put something out there that could potentially get someone hurt. Second – I didn’t actually run the wiring. The crew from Xantrex did most of the heavy lifting, and I was just there for approvals. And finally, since Xantrex designed and installed this system, it’s really their intellectual property. I don’t want to be giving away secrets that aren’t mine to give, ya know?
        The good news for you though, is that I don’t think there was anything all that unusual in the install. A competent installer who has installed RV inverters before should be able to figure things out.
        Sorry I can’t be more help, but hopefully you understand. Thanks!

        1. James - Post author

          I would just start with Customer Service. We’ve met members of that team and they should be able to help you. (They’re all super nice.)

        2. Steve Day

          Totally understand James. I was actually not looking for an actual “wiring diagram”, even though that is what I wrote. I should have worded it differently. I was hoping for an elementary sketch of the broad strokes involved in the flow of energy from alternator to battery, to inverter and how the stock transfer switch was involved. I will have a professional electrician that specializes in RV and boat inverter systems do the installation. I’m just trying to conceive of how to interface with the Travato’s AC system. I’m guessing you substituted the inverter feed in place of where the Onan used to connect. That would leave the transfer switch and everything beyond untouched, which would still allow the shore power override. I’ll send an email to Edge and say hello as well. Thanks for your reply, now get back to your fridge project!

        3. James - Post author

          Well, I can tell you this much:
          There is no more transfer switch because it is not needed. I tried to sell it on eBay but nobody wanted it so I threw it away.
          Incoming power goes through the surge protector and then to the inverter/charger. Inverter charger is wired directly to the inputs of the 120v circuit breaker panel.
          Generally speaking, there’s no point using more parts than are necessary.

    10. Vince

      Hey James. Looks like a great solution to protect the 2nd alternator. Better than the stock plastic shield provided by Roadtrek on my Zion. I too have scraped my protective shield on my fair share of curbs and am very conscious about the way that I park and drive now. I love the 2nd alternator but it does need more protection.

      I live in Santa Clara which is a few miles south of Mountain View down Highway 101. I’d love to be an early adopter. How much would it cost?

    11. Larry

      I came across these gadgets today. Looking at your last photo, they might be useful. I have no idea if they work, or how well they work, but it’s something worth investigating. Brandmotion makes two Curb Alert models but I can’t figure out the difference. There’s also one from a different company with a similar name, Curb-Alert.

      Curb Alert

      Curb Alert Pro


      There are probably similar units available from other manufacturers.

    12. Jim Weeks

      I read your pieces re the underhood generator you installed. As usual they were interesting and informative and very complex. My question is probably much too elementary and simplistic: Why did you need to do it in the first place? Wasn’t your engine already charging your coach batteries? Especially when you’re driving to your destination? Was this more a major upgrade and enhancement, particularly with the lithium battery?

      1. James - Post author

        Hi Jim – you are correct, the engine was already charging the house battery. But the second (and very expensive) lithium battery really needs to be charged differently from your basic engine starting battery. Had we just used the engine alternator for that, we would have been charging the lithium battery improperly and would have shortened its life. Also, the second alternator can give us hundreds of amps of charging. Had we used the engine alternator, we would have been limited to what was left over from the vehicle’s needs.

        Hope this helps your understanding!

    13. James Cynowa

      While I understand a quest to fix something that bothers you, i.e. “Rattles”. There is a cost vs benefit ratio. How much was involved vs. potential savings.

      Cost of materials + fabrication + time + lodging + added weight – cost of alternator= + or – ?

      I totally understand wanting the extra protection and I think the second alternator sits much to low. But is the total cost justifiable?

      Did you consider replacing your oil drain with a ball valve and hose? You could also relocate the filter to the same location and make oil changes a snap.

      With a ball valve on the oil drain it would also be easy to take a little oil out every month, then put it all back in just before a race. Oh, wait, wrong Lance.

      1. James - Post author

        OK. That’s the best Lance joke we’ve had on here in a long time. Well done, sir!
        As far as the expenses, yes, it hasn’t been an inexpensive affair. The hope is that we can get this down to something we can sell. I’m just considering all of this work as “product planning”. We may never make it up in the end, but at least we’re having fun!

        1. James Cynowa

          An alternator is a very resilient component. Before belt tensioners you used a pry bar on the alternator to tighten the engine belts. The case housing on alternators can really take some abuse. If you look closely at the picture of the curb your skid plate is near impact but your alternator still has clearance. Between the thickness of material and the insulating space you have actually given up about an inch of clearance. My fear would be an impact that would cause the plate to bend and contact the vibrating engine components.

        2. James - Post author

          Well, I suppose it all depends on what kind of impact we’re talking about. The guard is 1/8 thick steel. Any whack that can push it into the alternator is – I’m guessing – going to cause enough additional damage that I’d call it catastrophic. I don’t know how tough we’d have to make it to protect against that, but it would probably approach ridiculous. I think the less-disastrous impacts are more likely, and I’m satisfied with where we’re set the toughness.

          I had scraped the alternator on curbs prior to the first version of the guard. I actually scraped enough that it had started to file the casing of the alternator down. (Check out the first post for a pic.) Given that, I’m personally sold on the need for something like this.

          If I find that I’m scraping the skid plate too often, I could always attach something on the new bull bar that hangs a bit lower than that. A plastic scrape bar?

        3. James Cynowa

          I was actually going to suggest a deflector/ air dam ahead of the skid plate.

          Are you going to look into the change in underbody aerodynamics due to the skid plate?

        4. James - Post author

          Interesting idea, but I didn’t do any good “before” tests as a baseline.
          But if the mileage suddenly jumps an MPG or so, you can bet I’ll be crowing about it!

      2. James Cynowa

        I was looking all around the site and in a big gear shift from this post. Can we get your opinion on some bicycles.

        I am considering a new bicycle and was wondering your opinion on bicycle types. Especially “fat bikes”

        Good luck on the new MPG.

        1. James - Post author

          Well, the idea is cool, for sure.
          But I don’t have one, personally, so it’s tough for me to comment on them.
          Very specialized. Even if I had one and loved it, I don’t know if we would travel with one except on a dedicated winter trip.
          I also wonder how well they would fit on various bike racks?
          But again, like I said, I don’t have one personally, so can’t give too much of an opinion.

    14. Dave Howell

      Just a thought, we hit deer with our Travato in southern New Brunswick, and after towing the van back to Maine, we found out that the only thing that protected the radiator, air conditioning condenser, and various other cooling lines was a plastic rams head medallion and a plastic grill. These cooling components had no real protection and were mounted inches inside the plastic. Three tow truck adventures, one month and $7800 later, we were finally repaired.

      The body shop mounted, I believe, the exact same grill guard that you have. With a grill guard. one may have more sheet damage as the impact is spread over a wider area of the front of the van, but the better protection offered to the cooling components, helps, I hope, in maintaining driveability

      I think our grill guard is worth the investment and makes me feel better driving in our area that has lots of deer. At least it makes a good place to hang wet things to dry. Maybe helpful.

      1. James - Post author

        I hope neither I, nor any of our readers, ever hit a deer.
        But having said that, I think the picture of Lance without the plastic face tells the same story as yours. There’s not much to protect those up-front components. The grill guard is likely to help in those kinds of impacts.
        Glad you survived your deer incident OK!

    15. Mike Stanley

      70 pounds … any concern about the net effect on GVWR and CCC? Especially since you like to travel with outdoor equipment as well.

      1. James - Post author

        Good question, and that is something we considered up front. But I’ve weighed Lance, and we have about 1300 lbs of CCC to spare.
        For a (heavier) class C built on the ProMaster, this might be more of a consideration.

      2. Wes

        Somewheres is your second alternator “musings” I remember you saying that Winnebago would not delete the standard generator on a factory order because of the electrical. I also asked them to delete the generator and they refused. So my question is…are you carrying around 130 pounds of dead weight or did you have it removed after market and if so what did that entail. Thanks for all the great information. Ordering a 59k next week.

        1. James - Post author

          Our RV came from Winnebago with a generator. It is now gone.
          I removed it myself (well, I had help). It wasn’t terribly difficult… just awkward.
          Eventually even got the fuel tap plugged at the tank end.

    16. Scott

      Nice! I’ve been contemplating adding a second alternator to our (soon to arrive) home brew promaster rv, but really didn’t like the clearance. I’m in Mountain View, so this could be pretty easy once my van arrives.

    17. Winston

      We are converting a new 2016 159″ Promaster at this time. The conversion includes the Nations second alternator – – that we, too, feel must be protected (we can, and have, hit a surprising number of concrete barriers and other ‘stuff’). We’re nowhere close to California (Illinois and Michigan) but do have a very competent local mechanic who can participate.

    18. Tom Lavender

      Have you done a review on the New Paseo from Winnebago and I missed it? From what I have seen and read it looks like the Ideal B Van. We really like the Pleasure-Way Plateau FL. But unfortunately its on a MB chassis (too many bad MB experiences). The Paseo on the Ford Transit chassis looks like a perfect combo.

      Thanks for any input you may have

      1. James - Post author

        We haven’t done one of our formal reviews… yet. BUT!
        We did do a Facebook Live event where we walked through one at its debut at the Pomona RV show. Russ Garfin is in it as well.
        You can see it on the Winnebago Facebook Page.

      2. Pam Chipman

        What are your bad MB experiences? We also are attracted to the Plateau FL and are getting close to purchase as we continue our search..

    19. Dan

      Nice. And I am always concerned about retread waste on the roads, as it can do a lot of damage, really quickly. The idea of adding protection, even without the need to protect the second alternator, is attractive. That said, I won’t be driving to Mountain View any time soon… kind of far.


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