My rooftop AC won't stay running when underway

Michael, I remembered in your post that you had added the circuit to your block heater circuit. Call it irony or not but while working on installation of our flooring I discovered the block heater switch was not properly installed. The white (neutral) was not pushed in for a tight connection, the black (load) showed overheating, and worst of all in another junction box the wires were swapped so that the neutral had become constantly energized and the switch broke the neutral which is now the black wire... My thought was where you had connected to the circuit and if there would signs of overheating in your junction boxes or switch. I had noticed once that power on that circuit was undependable.

Update: At Gary's suggestion, I swapped the leads for the power cable and generator. I drove from Sherman, TX to Little Rock, AR with all of the air conditioners running. I had my test light connected and for the 5 1/2 hour ride, it didn't blink once. This definitively identifies the problem as the transfer switch and I think it has been faulty since I got the coach.

According to the owners manual, it is warranted for two years and I have had the motor home for about 26 months. I am going to attempt to get Winnebago to repair it, but I am not sure they will. I am not even sure how they can verify the problem with it.

Worst case is I'll suck it up and either attempt to fix it (unlikely) or I'll replace it.

Thanks to everyone for your help.

Here's a surprising update after talking with Winnebago and Parallax Power, the manufacturer of the transfer switch:

Winnebago agreed with my diagnosis that there was a problem with the transfer switch. Since the switch has a two year warranty, the rep recommended that I call Parallax. I did and spoke with a tech support rep there. His response was that their transfer switches are not designed to be powered while driving the coach. Because they are generator priority switches, when the generator is running, the contacts are held together with the relay. According to Parallax, there is no way they can design a relay that will remain closed during all kinds of road conditions. They won't replace it and cannot confirm that a replacement switch won't have the same problem, which they said exceeds their design requirements.

When I called Winnebago back, the rep was surprised by Parallax's response. He suggested that if this was common with their switches, he would have heard about it. I asked for a recommendation for a switch that was intended to be used while driving and he told me that Winnebago only uses Parallax switches. He suggested that I replace the switch, but I have a real problem with that. Why would I buy another transfer switch that the manufacturer says shouldn't be used. If it does the same thing, I will be the proud owner of two shoddy switches!

Apparently, Winnebago is installing transfer switches that are not intended to be energized while the coach is under way. I don't recall reading this in their manual and I don't think the guy that did the predelivery inspection mention that I should use the generator while moving, like I have done with my other two motor homes.

I have written an email to Parallax and copied Winnebago asking them to confirm what I was told. If this is true, everyone with a Winnebago coach should look into this and make sure you're not encountering the same problem. The only reason I know about it is because I added a roof air conditioner. With only basement air and road noise, there is no way most people would be aware that it was occurring. Constantly cycling the compressors on and off puts an awful lot of wear and tear on them. If Winnebago doesn't recommend to not use generators while under way, should they be on the hook for electrical system damage that is caused by this?

I don't know about you, but to me this is a BIG DEAL! I live in Texas and if I can't run the generator on the road, Winnebago needs to put a whole lot more resources in the dash air. When it's 100 degrees out, a handful of vents on the front isn't going to cut it. For now, I am leaving the switch wired backwards.

Winnie owners may want to give them a call to get position on this.

Michael, is this transfer switch mounted to a horizontal surface? If it is, it may be unlatching as the result of  bumps in the road. If there is room try mounting it vertically. If it's already mounted vertically....kindly disregard my suggestion.

It was factory installed vertically.

Further update:

I got a voicemail from customer relations Winnebago after I sent them a copy of the email I sent to Parallax. They confirmed that Parallax's official position is that the transfer switch should not be used energized while driving because it is not designed to do so. He reiterated that this was the first time he had heard of this and recommended that I replace the switch, thinking that it is a faulty switch. He was also curious what Parallax's response to me would be. I haven't received one from them, yet.

I am going to see if I can get Winnebago serious with them. It's one thing for them to blow off an individual with one of their products. It's another thing entirely to mess with a customer as big as Winnebago must be.

I am a little surprised that my original conclusion post didn't elicit a single response from anyone. I am surprised again that the second update only got a single response questioning the mounting position of the switch.

I have read many posts about how meticulous some posters are to make sure there are no heavy loads when switching from generator to shore power or vice versa. I am one of them. Wouldn't you be surprised if one or both of the legs of your transfer switch was constantly bouncing under heavy load, not because of something faulty, but because of a poor design and the conscious decision of the manufacturer? With basement air, this could be happening to you and you don't even know it. Wouldn't you want to question Winnebago about their official position on this?

(climbing down off my soapbox)

I'll report Parallax's response if/when I get it. In the meantime, an email from Progressive Dynamics assured me that their transfer switch was designed to work while the vehicle was in motion.

Stay on soapbox! I can't wait to see how this ends. You have me thinking about mine, maybe I should mount it in rubber or better yet maybe WINNIE SHOULD DO IT FOR YOU. Do you suppose Winnie knew this limitation from the beginning and accepted it due to price?

Who made the actual contactor inside the transfer switch assembly??  Is it one of the biggies like Square D or ????? some unknown brand?

I don't know if they did it on purpose to save money. When shopping for a new one, the Parallax unit isn't any less expensive than the other ones I have found. It's not really relevant to me. What's more important is what they do about it.

I don't know who made the relays. They are behind a shield and I wasn't going to take it apart if it was going to be replaced under warranty. Now that that option is out the window, I'll take it apart and see if there's something I can do to fix it.

I don't think the mounting position of a 'normal' relay should affect its holding power when held in the operated position by full operating current.  If the relay was normally in the released position (no current flow in the winding) and contact bounce breaks the contacts that is a relay/switch design problem, not enough contact spring tension or follow built into relay, not usually a problem with heavy, high current relays.

The vertical mounting position might be detrimental if it was a magnetic latching relay that is pulsed into the operating position and released using the opposite polarity of current. I doubt very much it is that sophisticated.

When I swapped the shore power and generator leads, the problem was eliminated entirely. This proved that the mechanics that hold the contacts normally closed (coils not energized) is sufficient. The problem is either somewhere in the power path to the relay coils or weakness in the coils to hold the contacts closed.

I would start out by replacing the relay/contactor that is in your transfer switch. This is just not right. It likely does not have enough holding strength to stay engaged. Of course RVs travel down the road with ACs on and the generator running. Remove your relay and take it to an electrical supply house. Buy a replacement in another brand like Square D.

Regards,
Aubrey Page
Sherman TX