A/C dysfunction: symptom of anomalous electrical system?

decland · Post by **decland** » 07 May 2009, 15:58

Trying to differentiate between A/C anomaly or larger electrical system dysfunction.

A/C blasts arctic at sustained intensity for five+ minutes then goes warm. Restarting the 96`850 reboots a/c-I don't know why-but the air conditioning stays cold for another 5+ minutes. This alternating cold to warm can be duplicated several times during a drive of twenty to fifty minutes.

Concurrently upon starting the vehicle-no problems however after a heavy rain there is a hesitation whilst starting the car. If left the car to rest it will not turn over-I use a portable charger and weeks go by without a problem.

I don't know if there is a problem with the alternator or battery or the A/C. I had a freon charge today and it worked just fine until I shut the car down and started it again in five minutes-and just like that it was blowing warm air.

In a land of shady mechanics ready to cannibalise I suspect the shop I visited for the Freon charge whose less than busy garage suggested a need for a new alternator with dangling suggestions that it "Just my be electical problems."

Resting battery at 12v + (I've checked the battery-no problems)

Post by **vegasjetskier** » 07 May 2009, 16:25

The few things that come to mind are a loose connection on one of the wires - maybe the compressor wire is shutting down the compressor, or perhaps a bad pressure sensor, or a relay getting hot and cutting out.

Does everything else continue to work when the AC goes warm?

decland · Post by **decland** » 07 May 2009, 16:40

Yes, everything works fine. There have been minor electrical problems, ie., the up-top third tail light worked intermittantly-an inconvenience pointed out to me by the local gendarme. After an exhaustive search for causality including a Volvo dealership I dissected the assembly and studied them. Initially nothing jumped out. So I ran a charge through the lamp-it worked fine and checked the ground wires in the left tail light area-no problems. Upon re-inspection of the upper tail light assembly I discovered a corrosion on the contact. By filing it down and bending it, contact was made and its been working fine since.
I've added this to illustrate the friable nature of the vehicle's electrical connections in hot/salty atmosphere.
I suspect your suggestions might reflect the condition.

Post by **vegasjetskier** » 07 May 2009, 17:53

It looks like there are two relays in the underhood box related to the AC. Look in positions 105 and 106. You could try swapping them with each other or other relays in the box that are the same and see if that makes any difference.

Also, your problem might be an excessive compressor clutch gap. Check out this link: https://www.matthewsvolvosite.com/forums ... c&start=20

decland · Post by **decland** » 07 May 2009, 19:27

Any photos or schematics of underhood box related to AC?
I don't know where that is.

With respect to the links:

Not sure about fussing around with the thermal switch.

The diagrams for tapping the center of compressr clutch plate would be tempting, but: that does seem perilous-photos or drawing of these procedures would help a lot.

Overall,
This -a/c failure- seems like a pretty common problem for these cars in warm climates.

Interesting how frequently folks-mechanics-try to pawn off an evaporator job without evaluating alternative interventions. I prefer 3rd world-ghetto repair procedures-People drive Volvos for hundreds of thousands of miles in extreme conditions-