1998 Volvo S70 AC compressor not turning on.

pb49415 · Post by **pb49415** » 05 Jul 2018, 13:33

Is going to ground on the negative battery post an acceptable choice for ground during this procedure or should I ground elsewhere? I know Power travels through the negative post during operations. Or should I connect to positive post. I always get a little confused on this.

dj_v70 · Post by **dj_v70** » 05 Jul 2018, 13:53

Yes, I would use battery negative terminal as ground as quick check.

pb49415 · Post by **pb49415** » 06 Jul 2018, 11:28

I checked for voltage on the low pressure sensor harness at the sensor with system on. I’m definitely getting 12v on one side of the harness terminal. I guess the dash control is functioning. From my understanding there’s another sensor of some sort to the left of the dash control/radio. Does that impact the system and the cycling of it?

dj_v70 · Post by **dj_v70** » 06 Jul 2018, 13:52

Assuming you verified voltage went away when you turned ac off, then yes, you verified dash control is ok.

It sounds like you troubleshot all of the major components except ecm, half of wiring and the input from dash (which I can’t figure out what it is for). You are ahead of me and troubleshooting my V70, I am out of state for next week.

If I was you, I’d retry testing at ecm cable. That assumes it is easy enough to take off (I never tried it). This would prove whether all of your wiring was ok. If that passes, i’d Try a junk yard ecm.

Let me know if you want to try testing on ecm wiring, I can put together a list of tests. However, need to see if cable connector can be disconnected and accessible for probing with voltmeter. Probably start by testing cable to your linear pressure sensor from ecm.

pb49415 · Post by **pb49415** » 06 Jul 2018, 19:37

I’m not sure if I want to take that leap of faith or fate. I’ll have to ponder over it. I can live without the AC for this year. May look into parting with the car anyways next year. My wife is planning to get an upgrade for hers next year. And I’ll take over her wheels. Not too concerned about resale valve on my s70. A couple hundred dollars difference isn’t going to break the bank. I’ll let you know. Feel free to send me your list anyway is case I get daring.
Thanks,
Paul

pb49415 · Post by **pb49415** » 07 Jul 2018, 12:08

I’ve got an idea. It possibly might work. It’s a 12v temperature relay switch. My thoughts are to add it in place of the compressor relay. Run the wiring into the interior of the car and let it cycle. Any thoughts on this idea? Please refer to attached link. There are multiple options on different switches offered.

https://www.amazon.com/gp/aw/d/B076M9JS ... Y5G6&psc=1

Post by **abscate** » 13 Jul 2018, 05:16

abscate wrote: ↑05 Jul 2018, 11:54 I think you have traced fault to where you arent getting a command signal to the relay from the ECC control unit (ECC is an abbreviation for Electronic Climate Control, but is often used to refer to the control unit in the dash)

I guess trying a junkyard ECC control unit might be next?

My post above I sent a fail

The ECM commands the AC relay to close , not the ECC control unit.

The problem here is the ECM only closes this relayafter processing multiple inputs from the ECC control unit, temp sensors, pressure sensors, engine load

Without seeing source code on the ECM, our troubleshooting ends here.

All you can really do is test wiring for continuity, contacts for cleanliness , and swap in known working parts.

1998 Volvo S70 AC compressor not turning on.

Re: 1998 Volvo S70 AC compressor not turning on.