OT GM A/C Question

My RV is a 1995 Chevy 1 Ton Van cab over style Class C with a 454 Throttle Body and factory AC.

1) Isnt the limit switch on the big shiny quart sized Receiver/Filter/Dryer (with the big rubber removeable plug) the Low Limit???? Im pretty sure it is. The input light green wire is hot ONLY when the AC inside dash switch is on and its ALWAYS CLOSED MADE UP i.e. the voltage on the light green input is transferred over to the dark green output ALL THE TIME.

2) According to the diagram I have, the 2 limit switches (high and low pressure cutouts) are in series and then go to feed voltage to the electric fan clutch so the compressor turns.

3) MY mechanic buddy has used his snap on gauges and BOTH the low and high pressure are correct AND IT COOLS FINE BUT ONLYYYYYYYYYY IF I HOT WIRE DIRECT TO THE CLUTCH

4) Its my "best guess" the other limit switch is bad and always OPEN because it never feeds voltage to the clutch. I have it jury rigged now taking the output (dark green) of the limit switch on the filter/dryer/receiver and jumping it direct to the clutch. That way it goes dead when the inside switch is off or the limit switch on the filter/dryer/receiver would open.

I guess iffffffffff the bad/open switch is the high pressure???????????? I run the risk of blowing a hose if she over pressurizes the way its jury rigged currently. I have not found the other (NOT on filter/dryer) limit switch so far but I havent looked real hard yet.



ISNT THE SWITCH ON THE FILTER/DRYER/RECEIVER WHERE THE PLUG IS THE LOW PRESSURE ONE??

The other (high pressure??) isnt up under the dash hard to find on the evaporator I hope!!!!!!

How risky is it to by pass jump the switch as Im now doing???

Sure, I know I need to get it fixed CORRECTLTY and will so eventually btu for now it works lol Its my best guess the other switch is the HP and its bad and open or else its a simple wiring problem, but theres just no voltage getting out of the one switch (on dryer) to the compressor clutch grrrrrrrrrrrrrrrrrrrrrrr

PS sure it "sounds" easy to just trace the wires (find other switch) but on that van its just not so easy to find things grrrrrrrrrrrr

God Bless yall

John T Just NOT an auto AC kinda guy

The switch on the RECEIVER /DRYER is the low pressure cut out. If it is open the compressor will not work as it sees the freon is low. You will need to recover the refrigerant and recharge. If it has the correct amount of refrigerant then the switch has failed.

The pressure switch on the ACCUMULATOR is the "clutch cycling switch" that cycles the compressor "off" when the evaporator pressure drops low enough to indicate it's about to start freezing up, allowing it to restart when the temperature/pressure in the evaporator comes up.

A side result is that it also acts to protect the compressor by shutting it off entirely as the refrigerant gets low or absent altogether.

The high limit switch MAY be in the compressor or nearby in the discharge line.

Any wires to the compressor besides the clutch connector?

Am I understanding you correctly that you still have the cycling switch IN the circuit but are bypassing ONLY the high limit?

Thanks Bob,

YOUR QUESTION
Any wires to the compressor besides the clutch connector? NO Just the little green wire and black ground clutch connector with the diode across it as GM used

YOUR QUESTION
Am I understanding you correctly that you still have the cycling switch IN the circuit but are bypassing ONLY the high limit?

YES, Im taking the output from the cycling switch (so it can still function if it opens thereby releasing the clutch) and jumping it to the compressor, by passing the high pressure wherever in the heck it is???? PS its (the switch I cant find unless its just wiring problem) always bad/open regardless if the compressor is engaged n pumping or not, ITS OPENNNNNNNN

Now whatcha think ????????????

Thanks Bob

John T

The refrigerant is fine, NOT LOW, she cools perfect so long as I jump the clutch so the compressor runs. The switch you mentioned IS CLOSED (as it should be because it has Freon) its NOT the problem

Thanks

John T

Hello John T,
If the low pressure switch is bad on the receiver you can check the voltage. Or a quick check is simply jump the switch at its terminals. If the switch is bad the jumper will cycle the clutch on and off each time you jump the wires. you have to have the system on calling for cooling to do so. A high pressure cutout switch , if you have one, would be on the high side, in series with the low side switch to the clutch.
Guido.

That switch (low presure on filter/dryer/receiver/accumulator) is working, it doesnt require jumped across, its currently closed because it has sufficient freon. Its just that somewhere AFTER IT (perhaps a bad/open high pressure cutout) the circuit is open so the AC clutch isnt getting voltage.

Thanks

John T

At this point you need to get a schematic and test the sensors that send signals to the control head.
You have not included the pressure or the weight of the refrigerant.
What should have taken a few minutes to diagnosis is confounded by distance.

The high pressure cutout should be near the top of the condenser on the passengers side. You might be able to see it by looking through the grill.

The high pressure switch is on the rear of the compressor.
The temperature and pressure it works with, the switch is probably bad. Dark green in and out.

Im not even sure it has any high pressure cutout??????????? Theres no wires going anywhere near the condensor (unless hidden), the wire comes from the output on the low pressure then in a loom (towards top of motor NOT towards condensor) and the same colored wire comes out of another loom to the clutch. Shes cooling fine with my jumper after the low pressure switch over to the clutch so the low switch is still in the equation MAYBE IM GOOD TO GO and its just a bad/open wire in one of those looms UNLESS theres a HP switch I havent located

John T

Thanks, I havent looked there because the whole top of the inner cover has to come off grrrrrrrrrrr

John T

My information source shows the high pressure switch on the back plate of the compressor. Have fun!

Hello John T,
If the low presuure switch is working, then you need to trace the wire going to the compressor.
Look for a spot where the wire is close to a braket with a sharp bent. Adjusting the belt sometimes requires a bar to get it tight, or replace it.
May be the wire got cut then.
Guido.

Just because it cools when jumping the low pressure swith doesn't mean it has a full charge.
I didn't see where you checked the pressure with a gauge. This should be your first step. HTH
WaltMo