another a/c puzzle

[mishalah]

1996 T&C LXi, 145,000 miles, F&R air, original a/c components. This spring I evacuated the system as it was not blowing very cold. Recharged, and was working pretty good until it got over 100. I checked the pressures, tried a little more freon, it seemed to do worse and the pressures started to go up instead of down so I let some gas out and let it stay with the low at approx. 35, hi approx. 200.

Again, it would work fine sometimes, blow warm others. After reading a ton of threads about the lack of cooling in these vans, I again added freaon and ran it a high rpms for about 20-30 minutes while we watched the guages, felt the air at the vents, and did a little water over the condensor testing. It would still vary from fairly cool, to cold, to warm depending on engine speed and whatever it felt like doing. Low about 25-30 at high rpms, high about 200.

We forced water through the condensor, which did make the pressures drop and run cooler. We inspected the condensor/radiator fins and couldn't see any debris. I drove it that evening with amb. temp about 85-90, and it cooled well. Drove it this morning with ambient temps about 90+ and it was ice cold the first trip, warm the second trip, cool but not really cold the third leg, and a little cooler on the way home (each leg about 5-6 miles in traffic).

I understand the less cool air when it's idling, but to go from very, very cold at the vents to blowing warm/neutral after it sat for about 40 minutes just doesn't make sense.

I think the fans are working properly, as I have replaced the module and switch twice. However, when we were doing the last fill and test there were times when the exra fan didn't come on. In fact, at one point the compressor shut off for a brief time. So....is that a high pressure release that cuts the flow to let the system cool, and could that be a source of the intermittent problem? I can't laways hear when the aux. fan comes on from inside the van.

[TXracefan1320]

I'm just learning about AC but I think your high side is too low. My 97 service manual says 290-380 psi at 90 degrees outside air. Maybe add another can? Also, do you have the same symptoms both front and rear? Mine was cold in front but hot in back, so I'm about to replace the rear expansion valve.

[mrtinker]

I can't over state it that you guys need to start this diagnosis knowing there are no leaks and that the refrigerant level is correct before even considering replacing an internal component such as an expansion valve. Just adding or removing refrigerant is going to get you into trouble here!

I recommend you verify the system is leak free and has a proper refrigerant charge in it before doing anything! Post your results here and hopefully we can help you from there.

Good Luck!

[mishalah]

Originally Posted by mrtinker

I can't over state it that you guys need to start this diagnosis knowing there are no leaks and that the refrigerant level is correct before even considering replacing an internal component such as an expansion valve. Just adding or removing refrigerant is going to get you into trouble here!

I recommend you verify the system is leak free and has a proper refrigerant charge in it before doing anything! Post your results here and hopefully we can help you from there.

Good Luck!

I have no known leaks. My system had never been opened in 15 years. When I did the recharge I vacuumed the system at -30 for over an hour, let it stand for another hour just to check, then began the charge. I put in exactly what the manual says (I have original factory manual set). My compressor could be a little tired, or my condensor could be getting clogged or the fins not clean enough, I guess. I was going to replace the Xvalve, but after a lot of researching I'm not sure that's the issue at all. The rear air seemed to be cooling about the same as the front, but I didn't really spend much time on it.

I do not want to overfill the system. The second time we added charge the high side went pretty far up (over 300), and the low side was returning to 50 at idle. After releasing some gas, running it around for a few days, we added some back in and monitored the pressures. Like I said, yesterday morning it was so cold I had to keep turning it down, but an hour later it blew warm until I ran the rpms up and held them at stop lights and drove in 1st or 2nd gear to keep the r's up above 2000. It finally got cool, but never as cold as it was the first time driving it.

[b1lk1]

When using the system when the van is first used for the day, the van has no heat soak. After driving it, you now have a hot engine, transmission, radiator, condenser, etc... To me, it sounds like something in the system, whether it is the compressor, condenser, or some other part becomes less efficient in the heat. I don't have a good answer to help other than to try and isolate anything that can be picking up and storing heat making it not work to capacity after warmed up.

[jpb53]

This link will explain how the fans are supposed to work.
http://www.automotiveforums.com/vbul...d.php?t=909708 The wiring diagram is for the fans. They are pulse width modulated and both run at the same time as you can see by the wiring diagram.

[mishalah]

Originally Posted by b1lk1

When using the system when the van is first used for the day, the van has no heat soak. After driving it, you now have a hot engine, transmission, radiator, condenser, etc... To me, it sounds like something in the system, whether it is the compressor, condenser, or some other part becomes less efficient in the heat. I don't have a good answer to help other than to try and isolate anything that can be picking up and storing heat making it not work to capacity after warmed up.

Exactly. The fans will both come on, but I'm not sure if they are coming on together at the right time. I'll try the water over the condensor again and see if that makes an immediate difference....though I'm not sure exactly what that will mean.

[Alphabravo]

Just a thought, have you checked the blend door?

[mishalah]

Originally Posted by Alphabravo

Just a thought, have you checked the blend door?

Hmmmmm. While I seem to get plenty of air through the vents I did notice that several times the fan seemed to crank it up and turn even higher all by itself.

But would that keep the air from blowing colder....oh...the heat/a/c blend. Hmmmmm...I'll check it out.

[mrtinker]

Hey y'all, good subject info here!

Looks to me like you might'a diagnosed the problem already.... The fact that you seen only one fan running instead of both. (according to someone else's post above)

Only one fan running would definately be a problem! I'd look there first.

I was wondering,,,, Does everyone here rely on a "Vacuum" test for leak checking? There's only 14.7 psi difference when leak checking a system this way. I always rely on nitrogen at 100psi to do my leak checks....

Any comments?

[mishalah]

Welllllll, it looks like the blend door is the problem. I have been out of town for a couple of weeks, but before I left I tried moving the slide control for both sides back and forth a few times when it started to blow hot. It immediately began blowing cooler. My wife has been fiddling with it since I've been gone and it works for her, but she says it's starting to take more manipulating.

I think that blend door system has servo motors to move the doors, meaning there's a good chance it's an electrical issue at the doors or controls. Has anyone here actually replaced any of the blend door components???

[Alphabravo]

I would first try to do a climate control calibration. Here's a link:

http://www.automotiveforums.com/vbul...er+calibration

The last paragraph of post #2 (by RIP) shows how to do it.

If that doesn't work, I would look into replacing climate control module itself. The fact that you have to "fiddle" with the controls tells me that the potentiometer on the sliders could be going bad. You should be able to get one fairly cheap from the junkyard.

If you need to change the blend door actuator, I think they are on the driver's side of the center console. Never had to change one, but it doesn't look too difficult, you'll just have to figure out which one to change.

Good luck.