AC compressor relay(switch in compressor)stops AC operation

[abscate]

Hi, I am looking at AC clutch not engaging problem on my 1998 S70. Looks like I need to check with this. Do you know how hard to access the compressor? Seems it is pretty deep down there and I cannot reach from top. I'd better try from bottom. A picture if any also will be very helpful.

And to apply 12V at the AC relay in main fuse box, do I just need to unplug the relay and jump short the two output pins with a paper clipper? From OP this could verify the problem but Is this adequate to engage the clutch even if the compressor switch is off? I thought the compressor switch is inline on the circuit to clutch.

Thanks a lot.

The AC thermal switch is in series to the 12 VDC supply to the compressor, so jumping the relay will NOT solve a AC thermal switch problem. The best way to do this is to cut the thermal switch out and solder the wires together, insulating correctly of course.

By the way, your 1998 S70 and 1999 XC in your profile are very different in the AC circuitry, as the 1999 has fly by wire where the AC control signals come from the ECU, not through the low pressure switch.

[goVolvo]

Yeh this is on 98' S70 only. 99' V70XC is another car. The problem is different now, see the last post. The low pressure was very high, 100psi but should be <50psi. Not sure if causing leaks.

[abscate]

The static low pressure ( compressor off) can be much higher than 100 psi. With the compressor running it should Be something like 25-35 psi.

The AC will not overheat the motor from cooling load. You need to troubleshoot that separately...bad cap, reservoir, or loose hose very common. If it's been overheated, head gasket, cracked head or block

[goVolvo]

The static low pressure ( compressor off) can be much higher than 100 psi. With the compressor running it should Be something like 25-35 psi.

The AC will not overheat the motor from cooling load. You need to troubleshoot that separately...bad cap, reservoir, or loose hose very common. If it's been overheated, head gasket, cracked head or block

Thanks. This is the first Summer with this car, so maybe cooling line has problem just surfaced now. It is not overheated. I'll let it idle for some time without AC to repro the problem. I'm too scared to drive it out now. And this radiator does not have its own cap, right? I only see a cap on the reservoir.

I just tried today again not shortcuting AC relay. Engine idles 20 minutes no problem. The AC button on dash bounce up immediately when clicked, the small round green LED goes on and off immediately. Looks like for some reason it does not try to turn on the AC relay. Meanwhile the AC relay seems good. I measured resistance on input pins 1-2 about 89ohm, output 3-4 0ohm 3-5 open. I also measured volt on pin 1-2, only 0.5v, no change when I press the AC dash button. Could even be the dash AC button switch problem?

Meanwhile, if I shortcut the output pin 3-5, even key is not on ignition switch, I hear clearly kah-dah sound, looks like AC clutch works fine. If I turn on engine like this, there is cool air flow. But I only tried for less than 1 minute. Don't want to see the coolant spill again before I'm determined to fix it.

[Ozark Lee]

Is this a manual climate unit or an electronic? They look similar but the electronic version has temperature graduations in numerical degrees and some AUT functions.

If you have the manual version the AC / REC switch itself is problematic. It is available as its own part but from the dealer it is pricey. You can often confirm the diagnosis of a bad switch by yanking out the radio and squeezing the switch. If things change at that point the switch is indeed bad.

...Lee

[goVolvo]

The dash is same as below pic. Base model. Should be manual switch. But I don't want to fix it now as the coolant (or maybe high pressure R134a) leaking steam is more frightening after AC runs for a few minutes.

[goVolvo]

I read more post about AC repairing. Seems there is a quick release somewhere that the refrigerant may spree out if pressure is too high. So it is possible if the high pressure sensor always gives too high reading (open circuit?) so the ECU never turned on the clutch relay.

The high pressure sensor (3pin) is on the high pressure pipe and located at the passenger side around the corner of ECU. I can piecing into the wire and measure volts on the pins. What value should be good reading on those pins?

If to replace the sensor, seems refrigerant has to be vacuumed out and the sensor has to be disconnected from high pressure pipe. I am not capable to do this though.

Found the other thread about high pressure switch. Good news is replacing it does not require refrigerant drain.

[Ozark Lee]

There is no designed pressure relief port on the car that would vent the system. If the pressures get too stupid high then a pipe or a seal can rupture but there is nothing designed to do so intentionally.

Either the low pressure or the high pressure switch can be replaced without recovering the refrigerant as they have a Schrader valve behind them. You will lose a touch of refrigerant but not much more than a "Pfft" if you remove the switches deliberately and the valves are working.

...Lee

[Manitoulin2003]

2002 V70-T5 A/C clutch stays engaged - does not stop turning when it cycles - and it cycles every 20 seconds. - Thoughts?

Thanks

[abscate]

2002 V70-T5 A/C clutch stays engaged - does not stop turning when it cycles - and it cycles every 20 seconds. - Thoughts?

Thanks

The only indicator of cycling is the clutch opening, so I’m not sure I understand your data.