Community Forums

Rickmd00 · 05-05-2015, 07:09 PM

Is it possible for the Evans Tempcon Rotory Control Panel switch to somehow develop an internal short? AC suddenly develop a problem. When the switch is turned from outside ventilation to AC, the fuse immediately blows. Any ideas?

Skip426 · 05-05-2015, 07:22 PM

I'll look at the wiring schematic for my Evans set up , but I think the dash control sends a signal to a relay for the compressor and evaporator fan that have a separate power through the relay , if that fuse isn't involved then the problem is in the control, or the relay.
With electrical anything is possible , I spent 34 years doing automotive electrical, for a living, to figure that out.

Rickmd00 · 05-05-2015, 08:10 PM

Quote:

Originally Posted by Skip426

I'll look at the wiring schematic for my Evans set up , but I think the dash control sends a signal to a relay for the compressor and evaporator fan that have a separate power through the relay , if that fuse isn't involved then the problem is in the control, or the relay.
With electrical anything is possible , I spent 34 years doing automotive electrical, for a living, to figure that out.

Thanks. I would like to see a copy of that wiring diagram. Evans will not provide info to a non-registered tech. The fuse that blows provides power to both a relay and a vacuum pump. The relay appears to go to a high pressure switch and also runs toward the back of the coach. I assume to the compressor but not certain.

Skip426 · 05-05-2015, 09:35 PM

Ok , that description doesn't match the schematic or what I have so Newmar may have had there own system wired up.
Is this a 25 amp fuse ?
Could you disconnect the wiring from the relay to the clutch , to narrow the search area down, by eliminating the A/C compressor clutch ( the biggest load on the system)
I'll scan this diagram through and post it but I'm sure you won't find it much use.
May be tomorrow before I can get to this, sorry.

EDIT: Forgot to ask is your coach on a Freightliner Chassis ?

Skip426 · 05-06-2015, 02:57 PM

Here's the image of the wiring schematic ; for what it's worth ; I think I could have done better when I was 10.
Note that the relay, vacuum pump and condenser fan are not shown, yet , at least on my coach ,they are powered by the same fuse. C/B in my case.
That's another thing you should check , if the condenser fan is jammed by debris, or seized that will blow the fuse too.

dennis45 · 05-06-2015, 05:01 PM

Loosen the compressor drive belt (with the engine stopped of course) and try to rotate the compressor drive. I had the same problem a few years ago and it turned out the Desiccant Dryer had come apart internally and distributed Desiccant beads through the system and caused the compressor to seize.
Expensive repair.
I'd start here and see if the compressor turns. Don't forget, the compressor clutch must be engaged to rotate the pulley. If the clutch is not engaged, the pulley will spin freely so you need to try to rotate the clutch housing closest to the compressor body. It should rotate by hand.

wa8yxm · 05-06-2015, 06:06 PM

Is it possible yes.. Is it common no.

More likely the problem is near the engine.. There is a wire that goes to the A/C compressor.. Just one... Inspect that wire.

If there is is a second short wire (often black) do not worry about that one it can NOT short to ground.... it IS ground.

Rickmd00 · 05-06-2015, 07:58 PM

Thanks everyone for the great suggestions. Turns out it was the condenser fan. It was frozen in place. I was looking for a short. Skip426's suggestion about disconnecting the compressor wire to eliminate the biggest load on the system got me away from searching for an actual wire that was shorted to ground. The fan was the easiest to check, and sure enough, it was locked up. In see where Skip426 reach the same possible conclusion as I was outside playing with the fan! Wow! You guys are good! The compressor/clutch was going to be the next thing to test. That's much more difficult to get to. Glad it was the fan. Thanks again.