Daily Archives: March 30, 2016

March 30, 2016   Uncategorized

Still on the Trail . . .

After coffee this morning, I got back to looking at my AC problem, this time starting to run tests at the control box from inside the unit.

AC Control Box_thumb[3]

The first test was to look for 12vdc between the ‘Y’ terminal and the ‘B’ terminal on the control box, and there’s where it went off the rails.

Instead of 12v, I found 0.77v, not quite enough. This voltage is what pulls in the relay that turns on the compressor. So if it’s not right, then no compressor, no cooling.

Looks like I’m on the right track.

Since this 12v signal is supposed to be coming from the thermostat, I thought I’d next eliminate the thermostat itself by swapping out the control heads between the front and back units..

Honeywell Thermostat_thumb[6]

I was hoping this might be a quick fix, but no. So next I measured the voltages on the thermostat base plate.

Honeywell Thermostat Base Plate_thumb[2]

To get a baseline on a working unit, I measured the voltages on the unit in the bedroom, and found that from the red wire connection on the left, I had 12v on the White, Yellow and Red wires. The switch is something I added a while back to let me manually switch between HIGH and LOW fan speeds.

But when I measured the unit up front, I got 12v, 5.9v and 12v. And the 5.9 volts is on the Yellow wire which is the compressor signal. So I’m still on the trail.

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OK, but why when I measure the voltage on the yellow wire at the control box I get .77v, but when I measure it at the thermostat base, I get 5.9 v. It’s supposed to be the same wire. I mean, according to the diagrams, it is.

But, next, when I checked the continuity between the two yellow wires, I get nothing. It’s completely open. But it couldn’t have been this way to start with. Otherwise it wouldn’t have worked . . . ever.

Then in looking over the Coleman diagrams again, I suddenly realized something. I don’t know where the 12v is coming from that feeds all this. On a home system there’s a 24VAC transformer that provides the power to the thermostat and to the relays. But this thermostat runs on 2 AA batteries.

Thinking maybe it was coming from the AC unit somehow, I switched off the breaker feeding the AC, and still found the 12, 5.9, 12 voltages at the thermostat base. So next I checked the rig’s12 volt fuse panel, but found nothing there either.

So the 12v must be coming from the rig somewhere, but where? The wires just feed out the side of the opening where the AC unit mounts and into the area between the roof and the ceiling, and the 120vac wires do just the same.

At this point I called it a night, and I’ll call American Coach tomorrow to see if they can help me out.

A number of you ask about Jan’s Funeral Potatoes recipe. First off, Jan will be the first to tell you it’s not hers, it’s Ree Drummond’s, from The Pioneer Woman cooking show. But if you want to try it out, I’ve posted it on Jan’s Favorite Recipe page.

Bon Appétit !

 

 

Thought for the Day:

“Of course I talk to myself, sometimes I need expert advice!!!”

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