Ac compressor clutch will not pull in

Good afternoon.

Did you check for two powers at the relay? 30 should have voltage and 86 should have voltage.

There is only one pressure switch. you need to verify 5 volt reference signal from the switch.



Roy

I checked and had both voltages at relay and had 5 volts at pressure switch.

Have changed relay.

Okay, the PCM is what grounds the control side of the relay when it gets the correct signal from the pressure switch.

You have a 5 volt reference, a ground and a signal wire that go from the pressure switch back to the PCM.

What are the pressures in the system?

Roy

35 and 135.

With jumper in, sorry.

85 low side and 35 high side jumper out not running.

High side went to 45.

High side slowly climbing at 55.

Okay, the 35 and 135 are not bad.

You will need to check that transducer or switch.

Back probe the switch. You should have 5 volts on the feed, one is ground and the other is the signal. Can you tell me the voltage on the signal wire?

Roy

3.2 volts.

Correction 4.6 did not have a good connection.

What color wire?

If that is the signal wire, that should be good enough to ground the relay and turn on the compressor.

Roy

Red and black - red wire is the signal.

Sorry, grey wire is 5 volts.

Okay.

You need to check the wire at the PCM next. Check the diagram and go to the connector and pin number. Back probe the wire for the relay control. See if there is any voltage there with it hooked up to the PCM.

Roy

I checked conductivity on both wires red-signal and the black ground from the pressure switch connector back to the PCM connector and they checked good. Could not get on connector to check the voltage with it plugged in.

Okay, you need to check the wire from the relay to the PCM. It is the dark green/white wire from the relay to the PCM. You need to see if there is voltage at that wire at the connector.

With the plug removed you should have voltage and when you plug it in, it should not have voltage.

Roy

I pulled the relay and probed the coil side of the relay in the base of the connector and I had power with relay out twelve volts, I reinstalled the relay and had some jumpers in with relay prongs and when I plugged the relay back in I lost power to the coil side of the relay. The voltage I had was twelve volts. I am assuming there is a triac output in the PCM is the reason for this?

The control side power is controlled by a fuse from the fuse block. The ground for the control side is controlled by the PCM and that is based on the signal from the pressure switch.

If the dark green/white wire has voltage, then it is not being commanded to ground. It should 0 volts if it is grounded.

Do you have a scan tool to monitor the operation of the AC commands?

Roy

I do not have a scan tool.

Okay, then if you cannot borrow one or rent one, then we will have to do this check manually as I suggested.

Roy

I am going to borrow a scan tool tomorrow and check it and I will let you know.

Sounds good. Keep me updated.

Roy

Carried car to shop and put the scan tool on it and the following is what we found:

1. The high side pressure sensor was reading or showing (444.92 psi).
2. The high side pressure sensor volts was (4.92 volts).
3. A/C relay command was (off).
4. A/C request signal was (no), but we had the switch on and blower on.
5. FC relay 1 command was (on).

We drain system and pulled the orifice and was very dirty and had look like alum metal shavings on it. I feel like the condenser maybe stopped up? So at this point I am not real sure if I need to replace it all and do not mind if it will fix it. We tried to force the compressor on with scan tool and it would not come on. Said it was on by the screen, so that is the problem is something else bad also like ECM also. Strange but the small line from the evaporator was ice cold but the large line was cool and got cool air out vents for a minute and then warmed up when we where checking everything with the jumper in contacts on relay base. Also, wondering about the high pressure seems real high. And I do need one of these scan tools they are nice?

Okay, yes 400 is way high. The aluminum is the key. I would suggest a compressor, condenser, orifice and a dryer. Flush the system of all debris.

No, to the ECM. It may have sent a command but the compressor did not kick on. That may be a compressor issue.

Roy

Okay, I will let you know what happens when I get all this done. Thanks

Sounds good. keep me updated.

Feel free to return with additional questions.

Roy