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Old 03-23-2021, 03:54 PM   #1
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Evans Tempcon cold control (thermostat) function?

Hello irv2:

Trying to troubleshoot the dash AC on my new-to-me 1999 Four Winds Hurricane (Ford F53).

I can't get the compressor to turn on, even when shorting the low pressure switch. My gauges say there is pressure but it's roughly the same on both sides (hi and low) so I'm thinking I need to get the compressor turning for a true read (right?).

I will mess around with the compressor itself, but before I do so I want to understand the role of the thermostat/cold control switch - I saw a schematic showing it in line before the pressure switches, and the coil on it that's usually sticking out of the black Evans box broke off in my hand -- so I'm wondering if that might be playing a role in my unit not starting. At 51k miles, I'd be surprised if it was the compressor itself, and with that thermostat obviously defective, I'd like to rule it out but don't want to take that box apart and start poking at stuff until I have more information.

The one thing I found at one point is that the thermostat stops the system from freezing up - which wouldn't be an issue now, so on the one hand I am seeing that it's broken, but OTOH, I'm also seeing that it might be irrelevant at this point. Is that thermostat usually closed unless it's too cold, or usually open unless it's warm enough? If it's normally closed, that tube shouldn't prevent anything else from going, right?

At this age, the unit's all vacuum-actuated, with some kind of spring-loaded switch on the outside that appears to then run to the low pressure switch. Tempted to mash that in and "mess" around and find out but don't want to destroy anything.
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Old 03-23-2021, 07:02 PM   #2
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This is all I have to offer;
https://www.proairllc.com/design-eng...empcon-guides/
As to not turning on, is the clutch getting 12V power and has a good ground?
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Old 03-24-2021, 12:18 PM   #3
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The electrical troubleshooting guide has promise. I'll report back when the rain stops and I feel like crawling around on the ground again :-)

Thanks Ray,IN
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Old 03-26-2021, 08:34 PM   #4
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The troubleshooting guide has my compressor as suspect. Now to find a guide for replacing it...
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Old 03-27-2021, 08:28 AM   #5
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You haven't got your compressor clutch to pull in yet right ?.....If you scroll through linked websights it shows several controls what does your look like.? I believe most vehicles have an AC fuse even though I did see one in diagrams. in the six or so diagrams I looked at it shows pressure switch after thermostat do you have power to either pressure switch wire.
I'm not familiar with the thermostat you mention can you supply a pic.
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Old 03-29-2021, 10:28 PM   #6
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Originally Posted by 153stars View Post
You haven't got your compressor clutch to pull in yet right ?.....If you scroll through linked websights it shows several controls what does your look like.? I believe most vehicles have an AC fuse even though I did see one in diagrams. in the six or so diagrams I looked at it shows pressure switch after thermostat do you have power to either pressure switch wire.
I'm not familiar with the thermostat you mention can you supply a pic.
I have bypassed the thermostat and pressure switch just for testing's sake - so the flow is 12v from the control switch straight to the pressure switch output. I don't have pictures because I haven't opened the Evans box yet but I believe it is this or similar to it: https://comfortairgr.com/shop/evans-...-culter-hammer, with the capillary tube broken off.

The pressure switch output is (from memory) red and ..white(?), spliced into a yellow wire which runs into the coach, under the dashboard, splices back into a red/white(?), then I couldn't find it - maybe that runs out to the relay box under the hood? I need to then find the wiring from there and trace it down to the compressor and see what I get down there ... I poked around a little bit and don't recall getting anything with my multimeter, and then applied 12v with my variable power supply and didn't get any response from the clutch, but I'm going to try both again when I get back home next week and hopefully after the ground dries out.

Changed fuses and swapped relays, no problems there.
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Old 03-30-2021, 06:43 AM   #7
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The capillary tube sounds like part of a TXV thermal expansion valve . Pressurized gas/vapor heats and adjusts freon pressure differential is strictly mechanical but you need it replaced unless its left over from an old replaced one. The wired thermostat you mention sounds like freezestat keeps coil from frosting over.
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Old 03-30-2021, 12:11 PM   #8
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Evans Tempcon cold control

My compressor clutch would not lock up with the 12v signal from the AC unit. I jumped with a good 12v line and she activated. I think all the length of wire from front to rear reduced the amps needed to lock - bad ground, resistance? When my new knees allow, I will use a relay to get a good connection. When I jumped the clutch, got cold air in the dash.
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Old 03-31-2021, 09:34 AM   #9
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Trust me it's very possible to get a 12 volt or any voltage reading on a multimeter but there's zero amperage available. Most breaks on a 12-volt wire happened right at the plug. Look for any butt connectors . You did good Try a 12 volt test light are breakouts a soldering iron and use an old light bulb and some wire.
It's good that compressor seems to function thus far. If the TXV capillary tube is damaged it may have a default position that works. Fingers crossed it's left over from a swap.
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Old 04-01-2021, 07:31 AM   #10
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Quote:
Originally Posted by blevtr View Post
My compressor clutch would not lock up with the 12v signal from the AC unit. I jumped with a good 12v line and she activated. I think all the length of wire from front to rear reduced the amps needed to lock - bad ground, resistance? When my new knees allow, I will use a relay to get a good connection. When I jumped the clutch, got cold air in the dash.
I can definitely vouch for there being about a mile of wire to go 10ft and really like the relay idea. I think I even have a spare relay and socket lying around. More testing needed when I get back home next week.
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Old 05-06-2021, 12:50 AM   #11
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To close the loop on my issue (at least as far as I'm concerned...)

I bypassed both the cold control and the low pressure switch, and neither of these got me any life

I removed the pulley from the compressor. It was quite rusty so I cleaned it up. No life.

Put 12v straight on the coil and actually got working AC.

Wired low pressure switch back in, still worked - so that wasn't it

Wired cold control back in, lost air - so I replaced that (I knew it was broken as I mentioned in my original post) and got working air again

Last culprit as yet unchecked = high pressure switch -- but for now, I redirected the AC switch wire from the control panel to a relay and ran a new wire down to the clutch. This setup costs me high pressure protection (when is that ever an issue in routine usage?), WOT shut-off and engine overtemp shutoff. I'm somewhat content with that but will still check the high pressure switch next week. Pretty sure everything in this system is original to 1999 so something's going to fail at some point and I'll deal with the high pressure switch then instead of discharging, flushing, and reassembling with old parts now.
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Old 05-06-2021, 12:57 AM   #12
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Quote:
Originally Posted by blevtr View Post
My compressor clutch would not lock up with the 12v signal from the AC unit. I jumped with a good 12v line and she activated. I think all the length of wire from front to rear reduced the amps needed to lock - bad ground, resistance? When my new knees allow, I will use a relay to get a good connection. When I jumped the clutch, got cold air in the dash.
So now you can rule out your compressor and whether there is enough freon. When turning on switch on dash to AC, you should be getting 12v at the pressure switch. Do you have that? Pressure switch should be cheap and simple to replace with very little freon loss.
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