|
|
When the engine is cold (first start) and I put the A/C on, it blows ice cold no matter how hot it is until I shut it off. On restart after a short shut down, the air out of the vents will just start to get cool (not cold) for a about a minute, then go warm and stay warm. Turning off the compressor for 15 minutes or so then turning it back on does nothing. Just warm air blowing out of the vents.
The next day, cold engine again, the A/C blows ice cold again until I shut it off and restart.
I have checked the following, the heater valve is in the closed position (no coolant to the core), the pressure in the low side pipe is 25-30 psi with the compressor running and engine fan running at idle speed. The accumulator is hot/very warm to the touch.
The air coming out of the middle, dash vents is noticeably warmer then either side vents when warm air is comming out.
I am baffled. Could use some advice.
Thanks, DEWFPO
--
1998 S90 077,400 and 1995 964 154,100
|
|
-
|
|
|
There is one thing that causes such behavior and is moisture in the system. I found out that by using the chippo plastic charging couplers I had bent the valve shaft in the low side port. In a couple of occasion later I could hear air being socked in when I was inspecting or toping the system with refrigerant. That caused the same symptoms you have and the total failure of the A/C eventually.
|
|
-
|
|
|
After all my diagnostic work, I couldn't find anything malfunctioning other than it wasn't cooling after everything got hot after a shut down. I added just a couple of ounces (1-2) of R134a and it is cooling very well now. I still don't understand why it would operate fine (32.6F out of the center vents) even in 92F temps until I shut if off. Maybe with the R134a being on the borderline, as the the temps went up it was not able to cool at all. I know the amount of r134a in the system is critical to it functioning properly. A lot moreso that R-12, you could be a little above or a littel underfilled and it would usually still cool just fine. I've been running it for the last few weeks this way and it's been cooling great even after very hot shutdowns.
DEWFPO
--
1998 S90 077,400 and 1995 964 154,100
|
|
-
|
|
|
Hello DEWFPO,
I'm not much of an AC guy, but for what its worth, let me offer some thoughts.
1.) On my Grand Caravan, a low side of 25-30 PSI is very low. On my van, if the ambient temperature is 90 degrees (f) then the low side should be 35-40 psi. So you could have a very low charge that kind of works--it would stop when the engine got hot.
2.) It would be a big help if you had the high side.
Best Regards,
Stan
|
|
-
|
|
|
Hi Stan,
I'm still checking things out. I verified this morning that I have no vacuum leaks in the HVAC vacuum system, including all te servos, and the check valve works. The pressostat on these cars is set to turn the compressor off at 23 psi and back on when it hits 45 psi.
Yeah, no high side port is a problem. Not sure why it's not there. We have a new 2007 Toyota and it's got both ports.
Thanks
DEWFPO
--
1998 S90 077,400 and 1995 964 154,100
|
|
-
|
|
|
Could your heat be on with out you knowing it. Maybe a vacuum leak in the climate control?
DanR 94 964 330,000 miles (96,000 on the new engine)
--
DanR
|
|
-
|
|
|
Hi DanR,
I've got plenty o airflow coming thru the dash vents (they are plugged off with a golf tee in the vacuum line due to a bad vacuum servo. And, I've added a vacuum check valve to the heater control valve line so that it maintains vacuum (closed). If will keep the heater control vlave close for a good 15 minutes after shut down.
Thanks for your thoughts.
DEWFPO
--
1998 S90 077,400 and 1995 964 154,100
|
|
-
|
|
|
It could never be something simple.
Good luck.
DanR
--
DanR
|
|
-
posted by
someone claiming to be David HUnter
on
Sat Jun 23 02:49 CST 2007 [ RELATED]
|
|
Can you clarify.
When this condition occurs are you saying the compressor is running yet the accumultor is warm?
|
|
-
|
|
|
Hi David,
Yes the compressor is running, the engine fan is on and the accumulator is very warm.
Thanks,
DEWFPO
--
1998 S90 077,400 and 1995 964 154,100
|
|
-
|
|
|
Hmmm. Compressor running, and - we assume - compressing refrigerant, which will heat it up.
Can there be a blockage in the system somewhere, frozen place or?? Is there supposed to be a fail-safe kick-out that has failed?
The symptoms of cold at first, then not, sound like a freeze-up somewhere. A real solid freeze-up. The time from hot air blowing to cold the next morning is likely a largee number of hours. How about a test to see if that number is smaller, just enough time for the freeze-up to thaw out. Maybe four hours, Two? Six?
Good Luck,
Bob
:>)
|
|
-
|
|
|
Thanks B.C.
When it's not cooling and the compressor is running, the low side pressure is 25-30 psi at idle, compressor not cycling. I consider this normal. I've shut the A/C off for upwards of 15 minutes with 100+ degree air blowing thru the dash vents so I don't think the evaporator is freezing. The accumulator is hot (ambient for the engine compartment). Next time I will check down by the VOV (variable orifice valve) on the frame. I can't think of any other place it could freeze. You would think that if it is a freeze up, leaving off for 15 minutes in that heat would free it up.
Good point though. The second time I turn it on during the day I just start to get a little cool air before it goes all warm.
I am wondering though ... If I had a blockage, wouldn't I see it on the low side. The suction side should go below 25 and the presostat would kick off.... ?
I'll check out your suggestion, Thanks!
DEWFPO
--
1998 S90 077,400 and 1995 964 154,100
|
|
-
|
|
|
Taking a low side reading at idle is not really a functional test. You need to bring the engine speed to 1500-2000 RPM to see what's happening. If the low side drops and you still have a warm accumulator, then you have a restriction somewhere. Since the car gets cold initially, a low charge is not likely.
A restriction will be evident by noting frost or sweating on its low side and dryness behind it. You fail to mention the temperature of the high-side pipe immediately after the orifice and further up at the evaporator inlet.
|
|
-
|
|
|
Thanks MapleLeafer,
I'll take temp readings and a few more observations as you suggest and report back.
DEWFPO
--
1998 S90 077,400 and 1995 964 154,100
|
|
-
|
|
|
I won't profess to being an expert but, have you checked the ac relay, under the passenger side dash. It may get hot, break the connection and even though you cut the power to the ac it may stay hot. Usually shows up as a little burned area where it arcs.
The last time I had my car in they told me there was a Volvo bulletin to bypass the temperator sensor on the back of the compressor. Although your symptoms don't sound like that to me it's also a possibility.
--
~William~ 1985 240 DL - 357,000 & 1998 V90 - 150,000
|
|
-
|
|
|
Thanks for your ideas Jacobite. I haven't checked the relay. The compressor does go on & off when I push the A/C button. The last time it happened I turned the A/C off for about 15 minutes in case it was the overheat circuit kicking in but even after 15 minutes of driving at 30 mph, and engaging the compressor.... no cold air. I could feel the compressor kick in as I was driving it but just warm air out.
The next day it's fine (on the first start of the day only). I can drive around town for a hour in 90+ heat and the A/C is ice cold.
Very perplexing.
Keep the ideas coming.
DEWFPO
--
1998 S90 077,400 and 1995 964 154,100
|
|
-
|
|
|
What are the high side pressures??? I know some volvos do not provide for high side hook up, But maybe the compressor is just worn out and gets worse as it warms up, sorta like an engine losing compression. Is it a new compressor?
Jeff
|
|
-
|
|
|
Hi,
The car doesn't have a high side port and I don't have a Scan Tool that can read them. It's not a new compressor but it doesn't have a lot of use.
Keep the thoughts coming.
Thanks,
DEWFPO
--
1998 S90 077,400 and 1995 964 154,100
|
|
|
|
|
