1998 v70 AC will not shut off

Post by **SonicAdventure** » 12 Dec 2015, 10:57

No matter what position the climate control switches are put in, my AC is constantly running. I always have a puddle of water under the car dripping from the evaporator.

My climate control is manual, and the AC button does appear to function as it lights up green when pressed. But, even when the fan switch is set to zero, the thing is still running. I can hear that steady hum in the dashboard that the AC makes.

What are some things to check? Can I just disconnect a fuse or relay as a temporary fix or would that mean I wouldn't get heat either?

Post by **cn90** » 12 Dec 2015, 11:02

Check the AC Relay.

Post by **SonicAdventure** » 12 Dec 2015, 13:14

Cn90, sorry, can you be a little more specific? I have no knowledge of car AC systems . Thanks

crlande · Post by **crlande** » 12 Dec 2015, 13:37

In the defrost setting the A/C is always on unless the fan is at zero. Make sure your control knobs are not broken since they will spin freely on the shaft and not actually be switching functions

Post by **SonicAdventure** » 12 Dec 2015, 13:53

Well, I have a feeling my knobs are working ok because when I turn it to cold I get cold, turn it to hot I get hot, and when I turn the directional dial I get air in the selected area. When the fan is at 0 it is definitely off, and with each turn past 0 it blows with more force. Both the recirculate and AC buttons seem to work, as when you press them once the light comes on, press them again the light goes off.

Last September the previous owner had a new compressor and radiator installed on the car, and the AC works fine - it just doesn't turn off !

NewVolvoUser · Post by **NewVolvoUser** » 12 Dec 2015, 14:01

My car does the opposite. No voltage to the AC clutch. I tried my friends control module, with the same result, no AC. I am right now searching for a schematic of the AC relay control circuit. Relevant leads are welcome.

Post by **SonicAdventure** » 14 Dec 2015, 20:50

Newvolvouser, your problem seems to be more common than mine...check the threads and YouTube esp. for the topic "AC clutch relay" and similar topics.

But I still can't figure out what is wrong with mine, and it's pointlessly killing my mpg while at the same time uselessly taxing my AC system by it running anytime the car is on.

any further input from anyone? Can I pull a fuse or relay and stop the compressor from kicking on??

Post by **cn90** » 14 Dec 2015, 21:11

I posted all the relays in the link below...

Scroll down to see the AC relay. For now, pull it until you figure it out, this way you can turn the AC off.
Another cause: someone installed the clutch wrong with no gap, so it is permanently engaged. With car off, what is the AC Clutch gap in mm?

https://www.matthewsvolvosite.com/forums ... hp?t=52252

Post by **abscate** » 15 Dec 2015, 17:38

Sonic..I'm a bit worried someone wired your compressor clutch always hot to solve some other problem with your AC system. Does your AC cycle while running ..do you hear the clutch clicking on and off every few seconds?

Post by **SonicAdventure** » 18 Dec 2015, 17:02

abscate wrote:Sonic..I'm a bit worried someone wired your compressor clutch always hot to solve some other problem with your AC system. Does your AC cycle while running ..do you hear the clutch clicking on and off every few seconds?

The funny thing is I don't think I've ever heard it shut off, but sometimes in the summer I remember getting the feeling that the AC had temporarily switched off when I was on a long car ride and then start blowing cold again after a few seconds.

Nowadays on my short commuting trips it seems like it is always on I never hear the compressor noise change no matter what buttons I press inside. And, I've recently checked out several other P80 Volvos and listened carefully to the sound the engine makes when the compressor is cut on...my car engine noise is always the same...and, I can hear that noise in the cabin of whatever the part near the firewall is condenser or evaporator, I don't know the term...but I always hear that thing making a hissing sound that a normal AC makes when its operating.