Roof top A/C's won't start

[casper124]

I went out today to ready my 06 Apex 40' for trip and tried to turn on a/c with no luck. Checked circuit breaker inside and went through switching them off and on again all the way through shutting down whole electrical system, unplugging shore power, switching off power switches in battery bay and turning on generator. I checked the thermostat and it appeared to be working and went through options with both zones, but, again no luck. Being that I'm new to the Alpine world I know I'm missing something simple or at least hope so....any ideas in the land of experts. P.S. all other systems seem to be working fine that I can determine.
Thanks for any ideas/help

Steve

[jesilvas]

Are your other 120V systems (microwave, TV, outlets) working? If so, that's good. If not, probably a transfer switch problem.
How long did you give for them to turn on?

[casper124]

Other systems are working. May have been under 10 minutes, not quite sure how though. Is there a time period to leave switch on before they will start ?

[jesilvas]

Yea but usually just a few seconds.
Maybe you have an EMS system that has turned them off? But if it were me, I'd check for 120V in the ceiling assemblies, then go from there.

[casper124]

What is the EMS ?

[pavepaws]

Check to see if you have voltage to the Air Conditioner unit. If it is present - turn OFF circuit breakers - voltage should not be present at the. Look for a burned up start capacitor, CAUTION - any existing capacitor may have stored an electrical charge...enough to knock you off the roof. Make sure all voltage is OFF, and short the capacitors with a shorting stick. If capacitor is obviously burnt up, replace it. The same for the fan motor assembly.

[casper124]

Ok...thinking someone who knows more than me might be better to check as if I hit the ground after being tossed by a/c charge, there will be seismic readings somewhere. Thanks,

Steve

[jesilvas]

Originally Posted by casper124

What is the EMS ?

Electrical management system.

Originally Posted by pavepaws

Check to see if you have voltage to the Air Conditioner unit. If it is present - turn OFF circuit breakers - voltage should not be present at the. Look for a burned up start capacitor, CAUTION - any existing capacitor may have stored an electrical charge...enough to knock you off the roof. Make sure all voltage is OFF, and short the capacitors with a shorting stick. If capacitor is obviously burnt up, replace it. The same for the fan motor assembly.

Voltage shouldn't be present? If they're going to work they should.
Voltage should be present, but if you're going to do more work, then yes, turn it off.

Originally Posted by casper124

Ok...thinking someone who knows more than me might be better to check as if I hit the ground after being tossed by a/c charge, there will be seismic readings somewhere. Thanks,

Steve

If you know nothing of 120V and 12V electrical systems, either take a class or get someone to do it. It's not hard, but you just have to learn first.

[clyon51]

Shooting in the dark here... If you have a Duo Therm digital thermostat with 2 Zones, are both ACs and furnace showing available on the display? I will assume so since you tried to turn them on.

On my unit, the Dometic - Duo Therm system does have a time delay on the ACs. It's about 4-5 mins. If you have Fan set to Auto, it could be that long before anything happens.

I would run this test which will let you know if there is power at the ACs. Start with Zone 1 and just use Fan mode on High. The fan should come on in a min or so. Do the same on Zone 2. If both fans work, you have ac power. If they don't work, you may not have ac power, but it could also be a blown 3amp fuse on the control board on each unit, which would also cause ACs not to work. I'll end here until we know what system you have.

[RedWing Nut]

Originally Posted by casper124

I went out today to ready my 06 Apex 40' for trip and tried to turn on a/c with no luck. Checked circuit breaker inside and went through switching them off and on again all the way through shutting down whole electrical system, unplugging shore power, switching off power switches in battery bay and turning on generator. I checked the thermostat and it appeared to be working and went through options with both zones, but, again no luck. Being that I'm new to the Alpine world I know I'm missing something simple or at least hope so....any ideas in the land of experts. P.S. all other systems seem to be working fine that I can determine.
Thanks for any ideas/help

Steve

You say you're new to the Alpine world. Have you ever had them running before?

[Jim A]

I would suggest cylon51's approach, especially if you are not comfortable with electrical work. It is an easy way to check if the A/C's have power. There is definitely a time delay between turning the A/C on and when it starts. I never timed it but it is probably in the 4-5 minute range. And it will seem like an eternity on a hot day!! (Not that you have those in Redding!)

It is hard to imagine that both A/C's would be bad at the same time.

[bruceisla]

Originally Posted by Jim A

I would suggest cylon51's approach, especially if you are not comfortable with electrical work. It is an easy way to check if the A/C's have power. There is definitely a time delay between turning the A/C on and when it starts. I never timed it but it is probably in the 4-5 minute range. And it will seem like an eternity on a hot day!! (Not that you have those in Redding!)

It is hard to imagine that both A/C's would be bad at the same time.

It's a 2 minute delay on Dometic/Duo Therm w/digital thermostat ... plus or minus a few seconds.

BTW, the common link here seems to be the thermostat. Although you can apparently change modes etc. it may not actually be communicating with the A/C controllers. The thermostat is linked to the controllers via a flat telephone cable. Typically, the cable is from the thermostat to #1 A/C and then from #1 A/C to #2 A/C. You could try removing the thermostat and reseating the phone cable (it's like a phone jack).

[Guido1967]

Took two days to trace and find the 12vdc supply wire to the thermostat that a mouse chewed through.
If you have 120 vac at the units check the 12 VDC supply at the thermostat.

[bruceisla]

Originally Posted by Guido1967

Took two days to trace and find the 12vdc supply wire to the thermostat that a mouse chewed through.
If you have 120 vac at the units check the 12 VDC supply at the thermostat.

Could be wrong but I think the thermostat is 12vdc powered .... if it switches modes and lights up it should have power.