2nd Gen Non-Engine/Transmission air conditioning

[SAndreasen]

i cant get the compressor clutch to kick on i hooked gauges up to the system have 60 psi low side high side zero do i need more refrigerant ? i hooked my power probe to the wires coming off the compressor have good continuity to ground on black wire had 12 volts on the blue wire so is my clutch bAD ?

 

[Tuesdak]

Looks like it. With 12v at the coil plug and clutch isn't coming on the magnet is open. (bad) I would double check the ground connection for the coil first or ohm out the clutch coil.

 

[Bill Stockard]

i cant get the compressor clutch to kick on i hooked gauges up to the system have 60 psi low side high side zero do i need more refrigerant ? i hooked my power probe to the wires coming off the compressor have good continuity to ground on black wire had 12 volts on the blue wire so is my clutch bAD ?

Something isn't right with your gauges if your gauges read 60 psi on the low side and 0-psi on the high side when the compressor isn't running. Are you sure the connection to the high side is correct? When the system is static, the pressure should be equalized on both sides.

Bill

 

[DavidC]

I agree if your hooked to High and low readings should equalize with a non running system. Save yourself some headache and recheck. I just did the Wife's Toyota yesterday that had voltage and ground. When I would unplug the compressor I would hear a clunk but no spinny. Ordered a new compressor from Rock Auto and 6 hrs later she had AC again. It was a sideways V6 so a little bit of a pain to change.

Dave

 

[SAndreasen]

ok ive been working on it again today . cannot get voltage to the compressor i removed and jumped the connector from the clutch cycle switch on the receiver drier like the fsm says still no voltage to compressor power probe shows a broken wire somewhere in that circuit so i gotta find that , old compressor clutch still wont cycle when i ground it ang give it 12 volts . what a pita

 

[JR]

Did you ohm your compressor out with a voltmeter? If it is open your compressor is burned up and is why you can't get it to kick on by jumping it.

 

[DavidC]

Do you have the wiring schematic ?. If not I can shoot you one for a 99


Dave

 

[SAndreasen]

thanks yes i have the schematic . i have ohmed the compressor no continuity so i need to install the new one anyway need to figure out the wiring first though

 

[DavidC]

The clutch 12+ goes through the ac clutch relay so if it is not energized you will show an open to the clutch. The relay coil gets it ground to energize thru the PCM. 12v+ to energize the ac relay comes from fuse 11 in the fuse junction on side of dash. If you already know all of this disregard and I will shut up.

Dave

 

[fest3er]

For the clutch to engage, the signal must pass through:

• B+
• ST-RUN ignition switch
• A/C Clutch Relay control circuit
• PCM
• Low pressure switch
• High pressure switch
• Dash control (must have A/C selected)
• Ground

If you're good with circuits, this should be enough to show you what to check.

It's possible your PCM has stopped passing the signal through.My '98's bypassed the PCM control for years.

Jumper the ground pin of the A/C clutch relay control to ground (not not for too long; if you let the compressor run too long with neither pressure switch in the circuit, you may need to change your trousers). This should activate the relay and cause the compressor to engage. If not, make sure the power side of the relay connects 12VDC to the compressor clutch and that the clutch works.

If the compressor works, jumper that relay control ground pin to the PCM side of the low pressure switch connector. This should make the A/C run normally; it should cycle normally and the dash control should turn it on and off. If so, your PCM has stopped controlling the compressor and you need to make the jumper permanent. The PCM isn't needed in the circuit anyway; rare is the Cummins 6B that can't make it up a hill with the A/C running.

If the compressor doesn't work, bypass each pressure switch (jumper each connector) in turn to see if either switch is bad. Low pressure switches don't last forever.

 

[SAndreasen]

thanks for the info i am going to try jumping the high psi switch and see what happens makes sense that maybe its bad because the relay is opening and closing fast so maybe that is the problem ill report back

 

[DavidC]

If the relay is cycling very fast it sounds like you are low on 134. My static pressures are around 120 on high and low at 90 degree's ambient temps.

Dave

 

[SAndreasen]

well ive been back at it again i have 12v at terminal 86 in the pdc box . when i send power to terminal 87a the clutch will engage . i tested the relay and it closes when i apply power also switched it with another relay still cant get the compressor clutch to engage on its own with the low psi switch bypassed .

 

[fest3er]

well ive been back at it again i have 12v at terminal 86 in the pdc box . when i send power to terminal 87a the clutch will engage . i tested the relay and it closes when i apply power also switched it with another relay still cant get the compressor clutch to engage on its own with the low psi switch bypassed .

If I read the SM right,

• Pin 30 should have B+ all the time
• Pin 86 should have B+ when the key is 'on'
• Pin 85 can be jumpered to ground to activate the relay
• Pin 87a is connected to the compressor clutch

One of the pins (the non-PCM-side pin) should be connected to ground when the dash switch selects an A/C mode.

If you ground pin 85 and the compressor engages, then it's almost guaranteed that the PCM no longer controls the A/C compressor.

 

[SAndreasen]

only power i have is at 86 no matter what i do not have voltage to any other pins when i send power to the 87a the clutch will engage the compressor clutch so i tried sending power from 86 to 87a via a jumper and now no power to 86 terminal

 

[fest3er]

Check the fuses again. There should be a smaller fuse for the A/C relay control and a larger fuse for the compressor clutch.

If you have power at 86, then the relay control should work; you should (barely) feel it click when someone turns the dash controls or key on and off (unless your arms are long enough to reach). If you don't have power at 30, then there's an open between 30 and B+, probably the fuse. If the fuses are OK, open the PDC box and inspect the wiring and connections inside.

 

[SAndreasen]

well i re checked the fuses replaced the blown 10 amp ac fuse now i have power at 30 but ive lost power at 86 .