V70-XC A/C high pressure switch?

[Ozark Lee]

Ray, you can replace either or both while holding the system charge on a 2000. That said, I don't think your description of the problems really point to a problem with either of the pressure switches.

Bad pressure switches typically result in the compressor not engaging, I've never heard of one arcing.

...Lee

[rainman]

Thank You Lee. I only have a innova 3160d scanner. It threw the P0532.This is all I could find;

Generic OBD Error Code Details for P0532
A/C Refrigerant Pressure Sensor "A" Circuit Low
What does this mean?
OBD Code P0532refers to
The powertrain control module (PCM) monitors the high side refrigerant pressure via a A/C refrigerant pressure sensor. When the pressure is high the signal voltage is high. When the pressure is low the signal voltage is low. When pressure is high the PCM commands the cooling fans on. When pressure is too high or too low the PCM will not allow the A/C compressor clutch to engage.
Symptoms
Possible sumptoms of OBD code P0532
- Engine Light ON (or Service Engine Soon Warning Light) - A/C Inoperative - A/C Blows Warm
Causes
Possible causes of OBD code P0532
- A/C system low or over charge with refrigerant - Faulty A/C refrigerant pressure sensor - Cooling fans in-operative - A/C refrigerant pressure sensor circuit open or shorted The Error code is generally activated on detection of the following conditions: The P0532 code is detected when the signal circuit is too low.
Possible Solutions
Volvo OBD Error Code Details for P0532
A/C pressure sensor Signal too low. Intermittent fault

The static grounding out noise I heard sounded like it was coming from where the low pressure switch is, by the firewall. I have looked at the wiring around that area and don't see any thing abnormal. If the pcm senses a fault and disables the compressor clutch, and because the cars/climate control is still calling for the A/C to be on, is it possible that the low side pressure dropped too low and in turn increased the high side out of range? Is that why this code can mean overcharged or pressure too low?

Also, with replacing the low side sensor by the firewall, can I assume there is a schrader type valve underneath the sensor when I unscrew it so I won't get blasted with refrigerant? I'm usually pretty carefull with things like these and would probably crack it loose, and them throw a shop towel over it and finish removing it with a small adjustable vise grip.
I think the low side sensor is 1/2 the cost of the high side one on the accumulator, so I think I would try that one first. Thank You Lee, Ray

[Ozark Lee]

When you unscrew the sensors be deliberate and having a shop towel around it isn't at all a bad idea. If you try to unscrew it real slowly it may actually leak quite a bit as the Schrader valve transitions to the closed position.

...Lee

[rainman]

Thanks for your help Lee, God I love this site Ray

[goVolvo]

Thanks for all the info and advice. I was told this same thing by my dealer. However, I ordered a new high pressure switch, and it had a spade on the underside for depressing a schrader valve, so I carefully unscrewed the old one. It popped a bit when the valve released, but that was it. So despite what we've been told, the high pressure switch has a schrader valve underneath it and can indeed be replaced without draining the system. I screwed the new one in, and now the A/C works like a champ. 45 degree air out of the vents, and it comes on when the auto climate control calls for it.

It's great you fixed it. I have a 1998 S70 with same problem. I probed the pin voltage of the high pressure switch. The voltage between left and right one is 5V. left and middle pin is 0.01V, middle pin and right pin 4.98V. Since I do have 70psi pressure in low side when compressor is not running, this seems showing enough of the problem with the high pressure switch.

But seems there is not adequate space to turn the wrench quickly there, to reduce R134a loss. I'll have to be careful and fast.

[goVolvo]

Today I got a used high pressure sensor and tried. There is progress. The voltage measured now is 4.0V, and if I jump short the clutch relay and compressor is running, the voltage falls gradually to about 2.2V. So this sensor is working. Also I can turn on the inner circulation fan on the climate control panel now, which was unable to turn on before. However the AC LED still cannot be turned on, and clutch does not engage.

I measure the low pressure wire and there is 11.9V, looks fine. So I am not sure what could still be problematic now. Just need more refrigerant? I guess even if there is little refrigerant the AC should still be able to engage. Or the low pressure sensor need to be replaced as well? I tried short-cut the low pressure sensor pins and it makes no difference. Anything else I need to check out?

Update: Oh good news. I disconnected battery for an hour, just to reset the ECU. Now it actually can start AC and blow cool air. Though it cannot keep running. If I press and hold AC button, it runs for several seconds then stop. If I turn the ventilation to windshield, AC LED stays on, and the compressor runs several seconds every 10 seconds or so. I measure the pressure at the low pressure service port, it goes down to below 25 (the green zone, maybe 15 to 20) when compressor runs, and bounces back to 45 when compressor stops.

What does this mean? Outside temperature is 60F quite low. I don't know what caused the compressor to stop running. Temperature too low? Maybe low pressure is too low and nothing much for the compressor to suck? Or high pressure reading is too high? So it is possible that the evaporator is kind of stuck? Maybe I'll just add some R134a and see if it makes difference or not.

[goVolvo]

Ah, I was simply confused by the pressure meter. Below 25psi is low, though it is marked as green zone. The normal range is from 25 to 50psi. I'll charge it to maybe 35psi in winter. Hopefully it will be all good.

[Ozark Lee]

The pressure gauge reading is only valid with the compressor running. The cutout on the low side switch seems to be at about 28 psi. A reading of 45 psi for static pressure without the compressor running is way too low unless ambient temps are Arctic. The static pressure readings are fairly meaningless since they are so temperature dependent but 45 psi isn't even close.

...Lee

[goVolvo]

I give up on this. Added two can of R134a and the pressure does not hold up. Apparently somewhere it leaked. Even I track it down it is too much for me to fix the leak and vacuum it. Let it be a winter car.

[abscate]

The evaporator cores go on these cars after 17 years. Its a cheap part but 10 hours stupid labour.I did my 1999 because I don't do summer heat well and the car is too nice to not drive in summer