Skip to main content ↑ ↓
Topic: Dash A/C Part Location (Read 415 times) previous topic - next topic

Dash A/C Part Location

Is there a biblical admonition about smugness? I was feeling pretty good about how well my dash A/C works until... Anyhow, hot air now. GaryB has helped me get started on diagnosing the issue.

Now I'm trying to find out where the high pressure switch is. Anyone know? Finally, I am told there is usually a fuse associated with it. I see on my schematic that I have two 30a auto resets up front (a/c fan and evap blower) and I have a relay and 15a auto reset back on the isolator board but that's all I see on the schematic - no fuse. Anyone know where it might be?

The problem I'm working on is a cycling compressor. It blows cold at start up but soon the compressor starts cycling and the air warms to ambient temp. I bypassed the thermostat that goes into the evaporator but the compressor continues to cycle. Thanks.

Here's a photo of my setup on the Grand Villa. You can see the condensor, fans, accumulator and evaporator. All we've got in back on the GVs is the compressor.
jor
93 225
95 300
97 270
99 320

Re: Dash A/C Part Location

Reply #1 –
On my coach, the high pressure switch is on a metal line very near the compressor. One time the connector came loose from the switch and shut down the compressor. It has remained secure since I pushed it firmly on the switch.

Have you put gauges on the lines? The pressures might give some clues regarding the problem. Are the fans on the condenser running? If they fail, pressures will rise and the system won't cool. Temperatures might rise enough to temporarily turn off the compressor via the high pressure switch. You may want to check the circuit breakers. One (or more) could have gotten weak and started cycling.

I replaced a cube relay that controlled the condenser fan. The spades had corroded enough that the relay would not supply power to the fan. One of your relays could have gotten flaky.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX
 

Re: Dash A/C Part Location

Reply #2 –
Cycling may be caused by high or low pressure or a loose wire, among things.

Our high pressure switch is screwed into a compressor output high pressure hose fitting located quite close to the compressor. Same with low pressure switch, but in the low pressure input hose. These fittings are equipped with valve cores similar to a tire stem, the prevent gas from coming out of fitting when replacing the switches, but sometimes the valve core fails to close and leaks when switch is removed.

When the dash air selector switch is turned on, 12 volts flows to one of the pressure switches, then to the other pressure switch and then to the compressor. You might say the switches are wired in series.

Putting a meter on the each switch will tell you if the 12 volts is being switched on & off before the pressure switches or by the low switch or by the high switch or by the compressor. Low switch opens when pressure is very low and high switch opens when pressure is above the switch psi rating. Both switches are closed almost all the time, engine off or on, when the correct amount of refrigerant is in the system. A temporary high pressure situation could cycle compressor.

Often he low pressure switch electrical contacts are manually closed to fill an empty system with refrigerant, because if the system internal pressure is too low, the compressor will not run to draw in refrigerant.