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Discussion Starter · #1 · (Edited)
AC will not come on. System has full refrigerant charge, low pressure switch is made. Compressor clutch mag is good, 4 ohms. No power present at compressor plug when AC turned on. Fuse is good, was not blown or replaced.
Problem seemed to start after replacing Power Master Brake system, but not completely sure about that. AC was working excellent up till last Fall. New lines, dryer and tested fine.
Any ideas ? I've checked that all relay connectors are on, but that is as far as I got without a wring diagram for the AC circuit.
High pressure switch has power to it,green wire but is open in both states to black & white & green & yellow ? Should a 3 way switch not be closed on one circuit ? ex NO/NC then switch on pressure ?
 

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fantasy tuner/investor
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The pressure switch on the line controls low and high fan, if you don;t have enough line pressure it won;t come on either it is inot a no/nc switch. Sounds like you have a bad AC head unit switch in the dash or a blown fuse, your missing.
 

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AC

AC will not come on. System has full refrigerant charge, low pressure switch is made. Compressor clutch mag is good, 4 ohms. No power present at compressor plug when AC turned on. Fuse is good, was not blown or replaced.
Problem seemed to start after replacing Power Master Brake system, but not completely sure about that. AC was working excellent up till last Fall. New lines, dryer and tested fine.
Any ideas ? I've checked that all relay connectors are on, but that is as far as I got without a wring diagram for the AC circuit.
High pressure switch has power to it,green wire but is open in both states to black & white & green & yellow ? Should a 3 way switch not be closed on one circuit ? ex NO/NC then switch on pressure ?
Is this one of those Touch Climate Control Unit?
 

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Homer Simpson
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1) Check the obvious stuff like the power to the circuit: does your blower fan work okay? Does your power trunk release work (if equipped - same circuit).

2) Start the car and check for voltage on the plug for the pressure switch by the accumulator. On the light green wire side it should be 12V with the A/C selected on in the car (Norm/Max/Bi Level) and no volts when selected off.

3) If you have good voltage here, shut off the car, jumper across this plug with a paper clip or a piece of wire, unplug the connector for the A/C compressor clutch, start the car back up and check for voltage at this connector (dark green wire side).

4) If you don't have voltage here you probably have a bad A/C cut out relay.
 

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Discussion Starter · #6 ·
1) Check the obvious stuff like the power to the circuit: does your blower fan work okay? Does your power trunk release work (if equipped - same circuit).

Yes, 25 amp fuse good

2) Start the car and check for voltage on the plug for the pressure switch by the accumulator. On the light green wire side it should be 12V with the A/C selected on in the car (Norm/Max/Bi Level) and no volts when selected off.

Checked, 12 Volts at plug, switch continuity verified

3) If you have good voltage here, shut off the car, jumper across this plug with a paper clip or a piece of wire, unplug the connector for the A/C compressor clutch, start the car back up and check for voltage at this connector (dark green wire side).

4) If you don't have voltage here you probably have a bad A/C cut out relay.
Which relay is for the AC Clutch, from relay diagram map, looks like relay to front of car on passneger side . Power across coil on this realy, but no main power.
 

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Homer Simpson
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Which relay is for the AC Clutch, from relay diagram map, looks like relay to front of car on passneger side . Power across coil on this realy, but no main power.
Yup, passenger side fender wall, closest to the front of the car.
If you don't have voltage at the connector to the compressor clutch, check across the contacts of the A/C cut out relay - the light blue wire and the dark green wire with a volt meter (the service manual warns not to use an ohm meter on any points connected to the ecm).
What do you mean about power across this coil but no main power? The pink/black wire is the supply to the cut out relay coil and the ecm energizes this coil by completing the circuit to ground. If the coil is picked up by the ecm and the contacts are open across the relay contacts (light blue wire 12V, dark green wire 0V) then you have a bad relay.
If this is what it looks like, try jumpering across the light blue/dark green wires and see if the compressor clutch picks up.
 

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Discussion Starter · #9 ·
Yup, passenger side fender wall, closest to the front of the car.
If you don't have voltage at the connector to the compressor clutch, check across the contacts of the A/C cut out relay - the light blue wire and the dark green wire with a volt meter (the service manual warns not to use an ohm meter on any points connected to the ecm).
What do you mean about power across this coil but no main power? The pink/black wire is the supply to the cut out relay coil and the ecm energizes this coil by completing the circuit to ground. If the coil is picked up by the ecm and the contacts are open across the relay contacts (light blue wire 12V, dark green wire 0V) then you have a bad relay.
If this is what it looks like, try jumpering across the light blue/dark green wires and see if the compressor clutch picks up.
Thought I measured power across the coil last night, but I have power on the contacts for the Compressor Relay. Jumpering the terminals there engages the compressor clutch mag. So something is keeping the Compressor Relay from picking up ?
 

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Homer Simpson
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If the coil is picked up then the ecm signal is good. If the contacts are still open then it is a bad relay. If the coil is not picked up then you need a scan tool to look at the ecm to see why it is bypassing the A/C. Its been a long time but I think full throttle will shut down the A/C.
 

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YOU KNOW MY NAME!
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As far as I know...laying into the loud pedal...will shutoff the AC.
 

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Discussion Starter · #12 ·
I appreciate all the help & input from forum members, but just cannot get the AC ( clutch mag relay ) to pick up. Off to the shop it goes next week & let them have a go at it.
 

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Discussion Starter · #13 ·
Follow up.
One thing I've noticed while searching issues is that once the problem has been located or corrected people do not post it, so here is what I found.
(1) AC clutch cut out relay intermittent, replaced it. & it was located in the most forward position on the gray plug, not second back as some relay location diagrams have them.
(2) AC Compressor high pressure switch on the backside of the compressor open. This was the hardest one to find, but once the problem was located, AC blows cold and everything works the way it should.
Along the way, also found that the coolant temperature sensor was not sending the correct signal for the actual engine temperature, reading lower than it should have, but not setting any faults.
All is good, many thanks to a few of the Forum members that helped me out with these issues, specifically 278cikiller. :cheers:
 

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AC Problem

Follow up.
One thing I've noticed while searching issues is that once the problem has been located or corrected people do not post it, so here is what I found.
(1) AC clutch cut out relay intermittent, replaced it. & it was located in the most forward position on the gray plug, not second back as some relay location diagrams have them.
(2) AC Compressor high pressure switch on the backside of the compressor open. This was the hardest one to find, but once the problem was located, AC blows cold and everything works the way it should.
Along the way, also found that the coolant temperature sensor was not sending the correct signal for the actual engine temperature, reading lower than it should have, but not setting any faults.
All is good, many thanks to a few of the Forum members that helped me out with these issues, specifically 278cikiller. :cheers:
No problem Don anytime,glad things are working awesome.:cheers:
 
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