Odd electrical ground / neutral issue on '89 370 classic

[Jammer]

Another way that mod is sometimes done is, instead of a switch, just put in a receptacle for the 20a side of the generator. Then plug into that for generator or connect an extension cord if using shore power. Breaks both hot and neutral and the switch is never in the wrong position.

[3 Dog Nite]

I agree with Jammer in post 16. Instead of using the SPDT switch, I would have went with a DPDT (double pole double throw). This way you would be separating the neutral as well. It's easy to change. Just add another white wire & do what you did with the hot black wire.

[romakdaddy]

I see what you are saying and its a good idea but Lowes didn't have any dpdt switches that I could find...might try one from the internet I guess.

[bkahler]

Originally Posted by romakdaddy

I see what you are saying and its a good idea but Lowes didn't have any dpdt switches that I could find...might try one from the internet I guess.

A proper DPDT switch with the right rating costs about $60. I did the same mod as 3 Dog Nite and it works like a charm. Highly recommended.

Here is the DPDT switch switch I used.

Brad

[romakdaddy]

got the right switch and I must say...it wasn't cheap.got one local for 70 bux and installed it the next day...I shouldn't have to worry now cept getting the front unit to cool...lol

[wxbuoy]

Maybe I am missing something or have a different set up (350). I have a SPDT switch that lets me choose whether to run the front or rear A/C when on shore power (both are fed on Generator). Is this the same on the 370?

Because, even if you used a DPDT switch on the Generator feed to the front A/C it is still not isolated since it shares a neutral on the SPDT switch to choose which A/C to run.... So wouldn't you also need to replace the A/C selector switch with a DPDT switch as well?

I could be wrong, and often am, but I was hoping to do the same mod and was looking at the wiring diagram in my manual.

[bkahler]

Dave,

Refer back to posts #17 and #18. The purpose for installing the switch is to allow running both air conditioners while connected to shore power. Typically these motorhomes are set up to allow only one of the two to run at a time on a 30 amp circuit.

What the switch does is allow you to bring in a separate 20 amp shore power cord , connect it to one side of the switch, the generator feed to the other side and the output goes to the rear a/c unit transfer switch.

With the switch in one position the a/c unit is powered from the generator (or factory shore power). In the other position it's powered from the new 20 amp shore power cord. This allows you run the front a/c unit via the rotary switch that selects which a/c unit, front or rear.

I have a sketch of how I did the wiring change on the 310. If I can dig it up I'll send you a copy.

All in all it's a nice wiring change to make.

Brad

[wxbuoy]

Brad,

I still don't see it. I understand the purpose, but fail to see how the Rear A/C gets a neutral if not tied together somewhere. Since the switch is a SPDT switch the hot is being shifted. But where are the A/C's getting neutral if not tied in. There are 2 Generator neutral ties ins on the main breaker panel and a magnetic transfer switch to switch the hots. I need to look at the switch over relays for the main and rear A/C again.... I am also going to go into the electrician at work ans say "splain this to me".

[romakdaddy]

on the 370 the front ac is only connected to the 20a side of the genny(most gens output 2 110v circuits) on the gen one side(30a) powers the coach side,same as the main shore cord. the other side(20a) is only connected to the front ac.there was no way to run the front unit without running the gen so I fixed it so I can run it from a drop cord connected to another 20a outlet.hope this clears it up.

[wxbuoy]

Thanks, that makes sense. On my 350 I can run both on generator and choose the front or the rear A/C to run via a SPDT switch the factory installed. I guess I need to pull the switch to see what it is doing so I can understand Brads point.