Automotive Air Conditioning Information Forum (Archives)

lyonkster on Fri September 18, 2015 3:16 PM

Year: 1997
Make: Chrysler
Model: Town and Country
Engine Size: 3.8
Refrigerant Type: R134
Ambient Temp: 80
Pressure Low: 45
Pressure High: 220
Country of Origin: United States

I would appreciate any help on how to tackle my AC issues. Quick background - van AC has worked well until recently, when I noticed the air was no longer cold. After full evacuation of R134, I connected a vacuum pump to it, and afterwards it held vacuum for over an hour with no change. So I assumed that the system was free of leaks.

I then filled it with the required 48 oz of R134, and it worked beautifully, vent temps of around 42F. That lasted about two months, when the vent temperatures moved back to the mid 60's (about 80F outside).

I then assumed that I had a leak that was only present with pressure but not vacuum (since it held vacuum just fine). I added a can of R134 with dye, but so far have not seen any signs of leaks. I also added another can of R134 just to see if that would bring down the vent temps at least temporarily. Oddly, that additional can did not reduce the vent temps, still about 65F on an 80F day.

Today I used the shop manual curve to determine whether my system was overcharged or undercharged. Using a thermocouple, I measured 114F on the liquid line, which is exactly in the right range of charge for 220 psi high pressure. So my system is supposedly not overcharged nor undercharged. Yet my vent temp is still 65F.

Where do I start with this??

Thanks in advance.

Cussboy on Fri September 18, 2015 3:35 PM

Quote
Originally posted by: lyonkster
I then filled it with the required 48 oz of R134, and it worked beautifully, vent temps of around 42F. That lasted about two months, when the vent temperatures moved back to the mid 60's (about 80F outside).

Where do I start with this??


I think you have a leak. Still.

lyonkster on Fri September 18, 2015 3:38 PM

Thanks for the reply. So I shouldn't trust the thermocouple readings? The shop manual suggests that this is way to determine level of charge. Also I'm puzzled why adding a can of R134 didn't decrease the vent temp.

Does it make sense to add another can of R134 and see what happens? If the issue is a leak, then that should improve the vent temps at least temporarily, right?

Edited: Fri September 18, 2015 at 3:39 PM by lyonkster

Dougflas on Fri September 18, 2015 5:13 PM

Since you do not know how much r134 is in the system, recover and recharge. You probably have a leak. Those evaporators were a trouble spot. If you added dye when you recharged it, check the drain tube for dye. A sniffer would do womders to help you find the leak.

lyonkster on Fri September 18, 2015 6:41 PM

I've tried the sniffer with no success so far. I haven't dug it into the evaporator area yet, but I have seen some members of the minivan forum have problems with their evaporators. Given how much work it is to get the evaporator out, I'd like to rule out the other suspects first .

So if I do have a leak and the vent temps are high because of that, should an added can of R134 drop the vent temp, thus confirming that the problem is with the system being low on R134? Seems like a very easy and cheap way to confirm the problem, or am I missing something?

Cussboy on Fri September 18, 2015 8:14 PM

Quote
Originally posted by: lyonkster
So if I do have a leak and the vent temps are high because of that, should an added can of R134 drop the vent temp, thus confirming that the problem is with the system being low on R134? Seems like a very easy and cheap way to confirm the problem, or am I missing something?

I think you're already decided upon trying this approach.

Before you try that, I'd get a good gauge set and read the high and low pressures at about 1500 rpm, a few minutes into running the AC, put an electric fan in front of the car blowing air through the grille too. If your high pressure side reads like 280 psi, I wouldn't add additional refrigerant. If it reads like 200 psi, then I would think that is reading low, and try the refrigerant addition.

My vehicles generally run in the high 200s for high side pressure at those conditions, not the low 200s. I'm in Arizona, just did a Yukon compressor in August when the heat here is pretty challenging, worked fine, read that high.
NEVER, EVER add a sealant or a refrigerant can that contains sealer or sealant, you'll ruin the system....NEVER, EVER add a sealant or a refrigerant can that contains sealer or sealant, you'll ruin the system....NEVER, EVER add a sealant or a refrigerant can that contains sealer or sealant, you'll ruin the system....NEVER, EVER add a sealant or a refrigerant can that contains sealer or sealant, you'll ruin the system....NEVER, EVER add a sealant or a refrigerant can that contains sealer or sealant, you'll ruin the system....NEVER, EVER add a sealant or a refrigerant can that contains sealer or sealant, you'll ruin the system....NEVER, EVER add a sealant or a refrigerant can that contains sealer or sealant, you'll ruin the system....NEVER, EVER add a sealant or a refrigerant can that contains sealer or sealant, you'll ruin the system....

GM Tech on Fri September 18, 2015 10:28 PM

It's a '97 Chrysler- most likely evaporator leak-seen a bunch in that era--also tranny will go out soon if not already

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

lyonkster on Sat September 19, 2015 12:28 AM

Quote
Originally posted by: Cussboy
Quote
Originally posted by: lyonkster
So if I do have a leak and the vent temps are high because of that, should an added can of R134 drop the vent temp, thus confirming that the problem is with the system being low on R134? Seems like a very easy and cheap way to confirm the problem, or am I missing something?



I think you're already decided upon trying this approach.

Only if it might help me diagnose the problem . Even though it'll be by far the easiest and cheapest thing to try at this point, I won't do it if you guys tell me that the results won't be meaningful and might confuse the issue.

Quote
Before you try that, I'd get a good gauge set and read the high and low pressures at about 1500 rpm, a few minutes into running the AC, put an electric fan in front of the car blowing air through the grille too. If your high pressure side reads like 280 psi, I wouldn't add additional refrigerant. If it reads like 200 psi, then I would think that is reading low, and try the refrigerant addition.

My vehicles generally run in the high 200s for high side pressure at those conditions, not the low 200s. I'm in Arizona, just did a Yukon compressor in August when the heat here is pretty challenging, worked fine, read that high.

Thanks, I'll give it a shot and report back.

lyonkster on Sat September 19, 2015 2:27 PM

An update - I ran the engine at 1500 RPM, and at 80F outside, I got 25-30 psi Low, 230 High, and 60F vent temp.

I added 6 oz R134, and at 1000 RPM I got 44 psi Low, 230 High, 55F vent.

Added 6 more oz, got 30 psi Low, 220 High, 50F vent.

The last set of numbers are almost within spec (37-49F at 80F), so that's progress.

I noticed that the compressor does not cycle at all, it is constantly engaged.

So does this mean I was low on refrigerant and need to find why? Or is something else wrong with my system? Should the fact that the compressor is not cycling tell me something?

lyonkster on Sat September 19, 2015 2:47 PM

Oh, forgot to say that I also measured the static Low side before adding any R134, it was 80 psi. And after the added R134, the static is 95 psi.

Edited: Sat September 19, 2015 at 2:53 PM by lyonkster