I have a 1999 V-70 with summer-time air conditioning. Summer the time it works and summer the time it doesn’t.

The AC works fine for anywhere from 5 minuets to 90 minuets. When the car is first started it’s great. Seems that after the engine gets to normal operating temperature, it stops cooling. I have noticed that the radiator/condenser fan does not automatically turn on when I first start the car with the ac on. It seems that the sensors controlling the compressor shut it down since there’s no fan running.
The radiator fan seems to work normally for just cooling the engine. No overheating and cars operating temp stays normal.
I was hoping someone might have a wiring diagram for the AC system so I can further troubleshoot the problem. I have checked and reseated all the related fuses and relays without any resolution.

I’d appreciate any advice.
Thanks.

 

Perhaps my inquiries for assistance are too complicated or mundane and that's why my last 3 posts/questions haven't been responded to.

 

Might help if you would post in the V70 section; just a thought..

I made a post awhile back that went into the AC fan wiring in detail but think it was for 850; willing to bet the wiring is the same on 99 S70. Will see if I can dig it up...

here it is; post #4:
https://volvoforums.com/forum/volvo-...ser-fan-55607/

is referring to 850 but again, may be helpful..

 

I don't know about that specific vehicle, but I would first check the high and low A/C pressures with the proper gauges to see if that is ok.

Then next on many vehicles there is an engine temperature sensor for the engine computer. On some vehicles this is a separate sensor from one which displays the engine temperature on the dash. (Again I'm not familiar with your specific vehicle - your vehicle may be different.)

Anyway under certain situations the engine computer will shut down the A/C. Like wide open throttle to give you more acceleration. Another is if it thinks the engine is overheating, which could be because the engine is actually overheating or the sensor is bad and indicating to the computer it is too hot.

So in the case of a vehicle with two separate engine temperature sensors, the dash one may indicate the engine temperature is ok, but the computer one may be telling the computer it is too hot. Thus shutting down the A/C.

Also the wiring associated with all this could have a poor connection or short and that could be the problem.

Anyway I would check the actual engine temperature with a thermometer, then determine if the various sensors are reading correctly. That can be with a computer hook-up to the vehicle or by measuring the resistance of the sensors as would be discussed in a factory service manual. And you would need those books anyway to see what sensors there are and how the A/C system works.

Also A/C systems have high and low pressure sensors. Too high or too low of refrigerant pressure and it will shut down.

Then there is typically a heat sensor on the A/C compressor. Too hot and it shuts down.

The above is generic info for all vehicles.