Air conditioner control relay location

[Kvsterling]

I’m having a new generator installed in 1984 excella 270. We are trying to locate the control relay for AC so we can use the auto start feature. Any ideas where it is located?

The shop say it’s the relay that low voltage signal turns on the high voltage for ac unit...

[Magnet18]

By AC, do you mean air conditioning, or alternating current?
What's the function of "auto start"? Do you mean remote start from the control panel?

[Air345Fly]

You don't say what AS you have.

In my 345 there are two transfer relays. These are the automatic
switches that transfer the AC circuits in the motorhome from shore
power to the generator. When the generator starts and comes up
to speed they delay a few seconds and then switch over.

In the 345 there are two such relays. One is under the forward bench
seat at the table. It controls AC power to the rear roof air conditioner.
It is mounted sideways on the generator box. It is hard to see into
without using a mirror.

The other one is under the bed in my unit with the sideways double
bed. Other bed arrangements are probably different. This relay
controls all other AC power in the motorhome.

My rear transfer relay failed. It would not change over. There is
a capacitor that controls the time delay. In my relay it had blown
apart. I got another one and it worked OK. A real simple and
cheap fix.

Pete.

[Air345Fly]

Originally Posted by Air345Fly

You don't say what AS you have.

You did say what model you have, my bad!


Pete.

[Kvsterling]

Have a 1984 270 excella. I’m referring to the air con unit. I’m realizing this was a newer ac unit installed at the airstream shop so I may need to dig around during my demo this winter. The new generator p30 control panel has a feature that sense when the thermostat turns on the Air con , the gen runs. Then when ac is off, gen turns off. I’m looking for that air con control box. Control panel will also sense low battery voltage and automatically turn on generator to recharge. Will be nice when boondocking

[WayneG]

My 84 270 does not have a relay (or 2nd AC unit) I only have a toggle switch over the stove that either goes to the microwave or the roof AC. I found some manual pages that indicate there may be different methods of wiring for the AC unit.
Edit to add, in my 84 270 the relay box shown in page 275 is behind the lower door, to the left of the fridge, it may be on the back side of the panel holding the circuit breaker box


I modified mine for power protection

[Kvsterling]

I have a mechanical switch on driver side for shore power and a separate switch for generator. I appreciate all this info! The module I’m trying to tap into is actually part of the roof air conditioner system, not the AC power for the RV. Believe I have a domestic penguin roof unit that apparently has a separate air con control unit that takes the thermostat signal and some relay in the unit that connects the 110v power to the compressor/blower. I can trace these wires but the disappear in the ceiling/wall and unable to trace. I heard some of these units are actually under the rooftop shroud on top of the condenser

[Kvsterling]

So to finish up this thread, I actually have a dometic ac with 5 button thermostat and needed a separate electronic control module with AGS trigger. I found the parts, hooked everything up (including a new thermostat) and no trigger signal. I am in touch with dometic customer support. They didn’t offer much and suggested getting it checked by a certified tech

As much as this makes me cringe, I don’t see much options at this point

[mayco]

Boy, I've never seen an air con. Set up that way with the genny. I may be misunderstanding but, you have a generator start relay in the air conditioning system that will start the genny , when not on shore power, and you turn on the ac???? Is there a delay built in so the genny has time to warm up before the load is applied? On my Onan 6500, it takes a good 30-60 seconds before voltage registers.

[Kvsterling]

That’s right, it’s called Auto Gen Start. Auto gen start also turns on if battery voltage drops too low and needs to recharge. These are all programmable parameters with Cummins Energy Command 30 generator control panel

Some dometic air conditioners have an AGS trigger off the control board. Mine needed a separate module controlled by the thermostat.

The idea would be that the thermostat recognizes the Air Con is to turn on, starts the generator, and then after a delay starts the fan/compressor. When it’s cooled off, the thermostat turns off the air conditioner and generator.

I’ve heard this is a tricky system to get working, but would be pretty neat if it does.