How can a 12vdc light cut off my A/C unit?

Check grounds

John Wayne wrote:
Just don't turn the A/C right back on give the A/C head pressure time to bleed off or you'll have a bigger problem.

My A/C units have a timer built-in that does not allow the compressor to kick in.

msmith1199 wrote:

allbrandauto wrote:
weird problems like that turn out to be ground problems

I'm no electrician myself, but every time I've had something screwy like this with anything electrical is has always been a ground problem. Weird how that works.

if your charger died and your batteries are low, turning on a light could be enough to lower your battery voltage below the operating level your thermostat requires, thus no AC.
try putting a charge (with an external charger) on the batteries overnight and then run the AC and lights, if your problem goes away, it was caused by a kaput charger and low battery charge.

allbrandauto wrote:
weird problems like that turn out to be ground problems

I'm no electrician myself, but every time I've had something screwy like this with anything electrical is has always been a ground problem. Weird how that works.

Thanks for the thoughts folks. To add to the weird issue, the coach batteries are no longer being charged by the converter. Had both batteries checked and they are good...cleaned off all terminals and batteries to see if corrosion was a problem but....same garbage. It appears the Magnetek 6345 had either bitten the dust or at least the charging portion has. Any ideas????

Mine did the same, turn on a 12 volt light with a single Ac running and mine would shut off for approx 3 minutes (time delay thermostat) Turn on light with both ac's running and same thing.

So far I replaced my rear thermostat and if my rear ac is running and I turn on a light all is good. Since I haven't replaced my front thermostat yet, and if it is running it will shut off when I turn on a light.

I am very confident once I replac my front thermostat all will be good.

I just changed the rear Friday and will do the front when I get back from my camping trip.

Think about this, a low (bad) battery. The converter is constantly trying to charge the battery you turn on a 12V light and it tasks the converter enough it glitches the 120VAC enough to shut down the AC.

Only other thing I can think of is a bad ground in the air conditioner 12V control board and ground is being supplied through the filament of the 12V lamps and when you turn on one of the lamps you lose the ground to the control board.

Long shot but it is a weird problem and I hope you post whatever you find.

Just don't turn the A/C right back on give the A/C head pressure time to bleed off or you'll have a bigger problem.

As noted the A/C likely uses 12 volts for command and control. If you loose 12 volt it shuts off.

If your batteries are low, and your converter is not converting. Or if you have bad connecitons in assorted areas.. Turning on the light may draw down the 12 volt beyond the minimum of A/C operation

Question is the light strong and bright or weak (Dim)? if Dim you have a 12 volt supply side issue.

weird problems like that turn out to be ground problems