Good Morning to all:

It was almost 80 degrees here in Norther VA yesterday so I decide to use the A/C in my 98 T5. I set it to the lowest temperature and and I hear the compressor kick on but no cold air. I do my errands get home and put my gauge on the low side port on the passenger side front of the car.

The compressor kicks on and pulls the low side from about 100 psi to 25 psi quickly. While the compressor is running it goes from 25-45 psi. It runs for maybe 10 minutes at the most and the compressor kicks off. If the fan runs at all it does for only about 5 seconds. The fan maybe kicks on every other cycle at the very most. The lower pipe into the firewall is cool but not nearly as chilly as the pipe on my friends dodge truck. The dryer (under the car beside the condenser) stays hot and never gets chilly. Thermometer in the register read only about 60 degress at best most of the time around 70 which at the time may have been very close to the ambient temperature. We also measured the voltage of the high pressure switch and it rose and fell in some relation to the pressure of the low side rising and falling. OBDII reading says the engine coolant temp is 239 degrees and the coolant temp gauge in the car is smack in the middle. i bought this car about 2 months ago, has 40k miles and it pretty much didn't move but a couple thousand miles over the last two years.

Of course, without the high side reading I cannot fully diagnose the problem but here are my theories.

The expansion valve and/or dryer are clogged somehow. The reasoning. If the high side is clogged it would not allow enough condensed 134a into the compressor leading to an only small amount of liquid refrigerant into the evaporator. The fan rarely kicking on leads me to believe that the high side never gets high enough to kick the fan on. Maybe a blocked driyer?

There may some other details that I am leaving out but ask away. My friend and I spent about 8 hours trying to diagnose the problem last night.

Any suggestions or theories are greatly appreciated. I really don't want to have to take this to the dealer to get fixed.

Thanks in advance,
Gino

 

Have you actually checked how much Freon is in the system?

What kind of scanner were you using on the OBDII?
If you can read real time Values then look in there good. Some will also show the A/C pressure.

 

We put in almost 12 oz of 134a but we don't know how much was in it initially. We almost overcharged the system but the symptom of a quicly cycling system did not occur.

The scanner was an Actron and we cannot read the realtime value of the high pressure side. BTW is 239 degrees hot for the 2.3 L?

 

Yes that is a little hot. Are you sure the engine is running that hot?
The sensor might be bad and reading high. Affecting the A/C.
Or the thermostat could be broke causing it to run hot.

I know it is a real bummer that Volvo never added a High Pressure port for testing.

Only on a Very few Ocassions I have seen the Reed Valves in the compressor go bad and it was like it was pumping Backwords. The high pressure lines would get Cold and the Low pressure Hot.

Do you have a Laser Temp guage? If so check the Temp at the thermostat housing and see what it is.

 

I do not have a laser temp gauge but i do have a thermcouple for my volt meter. Will that give me a true enough temp reading? I can do that tomorrow night if you feel that would diagnose the problem.

How I came up with the 239 degree number..........the obdII scanner said that the enging temp was 239 BUT the meter in the car was smack dab in the middle.

With all that said by you and myself..........i guess the temp sensor tells the computer the temperature and I can see if the car was hot it could throw things off.

The whole system seemed hot with the exception of the lower pipe going into the firewall.

Looks like we may be getting somewhere here .

It sounds like you think the coolant maybe hot.......AND OR the temp sensor is bad. It would seem to me that the thermostat would either be stuck open or closed and not in between.......pointing the possible culprit to be the sensor.

Don't think i'd have to drain any coolant to change the sensor....yes...no?

Thanks,
Gino

 

What about unplugging the temp sensor........does that buy us anything?

 

You don't have to drain the collant to change the Parts.
I suggested replacing the thermostat and sensor because it is easy to get the sensor out with the thermostat housing off.

The Thermostats are know to break.

The sensor for your meter should tell you pretty close to the engine temp.

Then compair it to the OBDII temp.

I would say the car Isn't overheating but the sensor says it is.

Unplugging will make the car go wacky. The cooling fan might stay on all the time.The A/C might not work at all either.

 

Ok as fate would have it the A/C started working today. When I got home I used the thermocouple on the thermostat housing at it read 174 degrees. The compressor was cycling normally and the fan stayed on the majority of the time. The register temp was about 53 degrees at it's lowest point. Not the ideal 45 degrees......is 53 close enough to the ball park that you would say it is running correctly? Next time I see my buddy I will check the computer reading of the engine temp.

On thing I left out was the morning before all this happened I covered up the alternator and degreased the engine. After spraying it down I had a bunch of misfires etc. I think maybe I goofed the temperature sensor during this operation. Being that the misfire stopped I thought all problems related to the engine cleaning had ceased.

BTW where is this temp sensor?

Thanks,
Gino

 

I doubt the cleaning had anything to do with it.

The sensor is in the thermostat housing. Under the upper Radiator hose.

 

Tech,

Maybe that is why i did not see the sensor this evening . I'll check the computer reading again soon and find out what it says and get back to you. You have been a tremendous help. I see that they offer a range of thermostats from i think 170 to 195. Which one do you suggest for my 98 T5?

Thanks,
Gino

 

I think it is a 180

 

I rechecked the computer reading of the engine temp yesterday and it read 174......a/c cycling normally. I think the engine washing goofed some of the electronics.

Kinda sad. In my 00 Jeep Wrangler....I just cover the alternator and wash away with no problems. Oh well.....no car is perfect.

 

Keep us posted from time to time on the A/C.

 

The A/C has been acting up again. As a result I decided to change the coolant temp sensor and thermostat. It looked like a pain to remove the entire housing so I was able to get the thermostat housing off (2 torx bolts). Upon putting the housing back on I buggered up the threads a bit but it looks like it will hold.

Is it normally necessary to take the entire housing off (housing that holds the temp sensor and thermostat) to to do this job? It looked like I would have had to remove the PS pump to do this . Hopefully the repair will hold and not start leaking.

Anyway, the end result is that the compressor just wont cycle for very long. It cycles for about 3-4 seconds and just kicks off. I have hooked up my pressure guage and it appears to be running within acceptable ranges. In fact even when it kicks off, it nevery really builds up much pressure.

Suggestions please?

Thanks,
Gino

 

Being that there has been no apparent change in behavior with the fixes from my previous post, I was thinking of replacing the aux fan switch with the one I removed for the thermostat housing. Something has to be wrong with it since I actually rarely see the fan kick on and if it does it will only do it for a few seconds.....never more than 10 or so.

Can someone tell me where this sensor is located? radiator?

Thanks,
Gino

If this doesn't work I guess i'll have to concede that something is very wrong with the compressor .

 

The sensor you changed controls the Fan.
What do you have the Fan speed at inside the car?
What is the pressures?
Are you sure you have enough freon in there?

 

Blower speed can be on high for an hour or on low.....the compressor cycles the same. The pressure goes between 20 and 45 psi. pretty sure there is enough freon. It only cycles for a few seconds so getting more in there is a little difficult. I don't have a high side port so can't measre that.

 

If the Cooling fan doesn't come on after turning the A/C on then the cooling fan,Relay,or High pressure switch might be bad.

Try driving it on the highway with good air flow and see if it gets cool at all in the car.
That would also point you to the coolong fan.

 

The behavior on the highway is the same. It gets a little cooler but not by much...cycling intervals are about the same. Where is the high pressure switch? How easy is it to get to? Is this what is called the pressostat?
Thanks for your suggestion . BTW the fan does come on when the temp gets high so can I assume the relay is ok?

Thanks,
Gino

 

Yes they call it a Preostat/pressostat.
It is located about 8-10 inches infront of the low pressure port on the high side line.
It is easy to get to.
Sounds like the A/C isn't kicking the fan on at the proper time.
If it gets a little cooler driving on the highway that might be the Fan.
When the ran runs the Highpressure will stay lower.

Check the wiring diagram for the car to see the A/C circuit for the Fan.
http://www.volvotechinfo.com/WD123/