2nd ac unit not coming on

Slojoe72 wrote:
Well new to me motorhome. Just trying to figure stuff out 1 thing at a time. Previous owner not much help. It's a 99 holiday rambler imperial 40' cummins 350.
Only front ac unit comes on when generator is running. Thing I noticed
Motorhome only seems to have one ac thermostat. It's by the dinning room and it's a duo temp electronic thermo. Now there is a 2 wire plug in the bedroom on the one nightstand but nothing connected to it (could that be a place where a thermostat was/goes.
Other thing I noticed was on the electrical panel. The heart interface only says the incoming ac breaker amps says 30.
Sooooooo
Thanks for helping in advance.

First check the 20amp breaker on the generator as it only feeds the rear air and nothing else. Sometime in the future, you might want to think about splitting that circuit with a plug and mounted outlet in the basement, so that you can run the rear air on a separate 20amp pedestal circuit in hot weather and leaving a full 30amps for the rest of coach.
Also, I checked for a newbie 2005 HR owner the other day and found that zone 2 was off. Their thermo was in in the hall and a two zone like mine, which has a sensor in the bedroom as well.
Seems that you got it now, so all is well that ends well.

DOUGRAINER ............... IS THE MAN. Im not sure how I missed your post.
You my friend are exactly correct. I went out and held those 2 button down and it switched from zone 1 to zone 2 and a minute later I got the other ac unit to turn on. thank you so so much.

Slojoe72 wrote:
Shouldn't I have 2 thromostats?
and what could that 2 wire plug be by the night stand in the bed room.

\

As I stated, there is no such thing as a 2 wire tstat. That "may" be the rear Zone temp thermistor wire and the Thermister is missing. You have failed to respond to a request----Does your existing tstat have an LCD screen or does it have black buttons and a black slider temp control? Doug

Slojoe72 wrote:
And once apon a time there was something screwed there because there is 2 small screw holes in the wall .

You may have solved your own mystery!

Shouldn't I have 2 thromostats?
and what could that 2 wire plug be by the night stand in the bed room.

dougrainer wrote:
IF the Motorhome came with 2 AC units the OEM always installed a large enough Genset to run BOTH AC units. A 5K and larger will run 2 Roof AC units. Doug

I bow to your greater experience......but I'm not sure it "always" applies.

I'm pretty sure I've seen some units with 50 amp service and a generator that will only run one. Maybe that was a class C or 5th wheel.

Anyway, 7500 should be plenty.

If it was made that way initially, I don't understand why it would work differently on shore power though......unless maybe the first one starts and drags the voltage down to where the second one won't start.

Probably not a "easy" fix and likely will require professional service.,

7500 ONAN DIESEL

Vulcan Rider wrote:
What size is the Genset ?

In many (most?) cases, it will only support ONE AC and not both.

If you have a 4K generator that is the case......and you need to be connected to 50 amp shore power to run both.

Just the opposite, In many(ALL) cases, the Genset on a 50 amp RV will run BOTH AC units. In many(MOST) cases, IF the Motorhome came with 2 AC units the OEM always installed a large enough Genset to run BOTH AC units. A 5K and larger will run 2 Roof AC units. Doug

NO Dometic Tstat will have 2 wires, so that plug is NOT for a tstat. IF your front tstat has the LCD screen(4 button CCC), THAT controls BOTH AC units. You should see ZONE 1 on the display. You need to push FAN and MODE at the same time to switch between Zone 1(front AC) and Zone 2(rear AC). The BAD news is this, they discontinued the 4 button tstat CCC in 2001 due to problems switching zones and other parameters. So, you may have a problem switching Zones, which is a defective Tstat. They are no longer available and there are some companies that attempt to repair them with good success. The wiring on your tstat is Phone TYPE 4 wire cable, so you CANNOT install any other kind of Tstat except what Dometic offers. Respond if this is what you have and I will go into more detail on your options. Doug
Copy and paste this link for your tstat.
http://bryantrv.com/docs2/docs/ccc.pdf

What size is the Genset ?

In many (most?) cases, it will only support ONE AC and not both.

If you have a 4K generator that is the case......and you need to be connected to 50 amp shore power to run both.