Ideas about air conditioning problem?

[ksing44]

I am still a little afraid that I may have the dreaded and expensive air conditioning failure noted for these cars. Last year, in June, the air conditioning was recharged and filled with the fluorescent indicator dye. Then in the fall I thought the system was fading, but with the cooler weather coming I just thought I wouldn’t worry about it until the spring. Sure enough, it isn’t very cold this year. I thought it needed to be recharged a second time, so I was sure I was going to have to rip out the entire dash and pay the whopping $2500 bill for the fix. I was willing to pay, but I was concerned about getting the dash reinstalled. Then last week I took the car to the very good independent mechanic that did the recharging of the system and he told me that the pressure of the system was fine. He told me that he thought the refrigerant had not leaked out. He also tested the temperature from the vents and he told me the temperature seemed OK. It was a rather cold day, however, and the outside temperature was virtually the same as properly cooled air. On a hot day, the air conditioning does not get anywhere near as cold as it did before. Since the independent mechanic couldn’t identify the problem, I made an appointment with the dealer for the 19th of June and I am hoping they can solve the problem. Since the pressure is good, I am hoping it isn’t leaking from the evaporator located under the dash. Could it be that the independent mechanics messed up a bit and charged the system improperly? Could the pressure be OK and not have the proper amount of refrigerant? I read about being sure to dry the system before recharging and being sure to fill the system with the appropriate amount of refrigerant. I am hoping it is simple, but I am willing to pay what ever it takes to keep the car like new. I just hope the dealer can figure out the problem. If you guys have any tips about the possible problems, I would be grateful to hear about them.
[?]

[SHIFT_diesel]

OK, I have a 1987 300D Turbo, A/C doesn't work. I have no clue whats wrong with it (yeah, thats very helpful to anyone trying to help [;)]). I've been told that the condenser is the faulty item. Is there anyway i can find out without visiting a mechanic? Thanks in advanced

[Kestas]

ksing, what vent temperatures are you getting? Is the compressor cycling normally? You also mentioned there was fluorescent dye in the system. May I assume no leaks were found? I know it's hard to judge a/c performance with the cold spring we've been having.

Jason, the only way to begin assessing the condition of your a/c is to connect manifold gauges to measure the pressures - static and operating. How did somebody figure that your condenser is faulty?

[ksing44]

I returned the car soon after the original recharging of the system so that the mechanic could search for a leak, but he never found it with his UV light. Then the dealer told me that sometimes it takes multiple loads of dye for the indicator to be visible in such places as the moisture drainage holes coming from the evaporator. I figured I would have to go back a few times to recharge the system to find the problem, but now the mechanic is telling me that there was no loss of pressure and I am confused about the original loss of pressure and the lack of sufficient cooling. T he air conditioning system must have leaked the first time, but that occurred over an 8-year period of time, so I guess it is possible that a loss of pressure isn’t really unusual for an "older car". I was kind of hoping that maybe a very slow loss of charge over 8 years didn’t necessarily mean that there was an obvious leak that would need immediate repair. If I had to get a recharge every 5 years, or even every season, it wouldn’t be so bad. Now however, it didn’t leak, but it isn’t cold.

The mechanic measured the vent temperature at 40 degrees, which he said was normal. However, as I said in the original post, it was a cold day so it didn’t take a lot of cooling to reach 40 degrees. The system does seem to cycle properly. I can feel and hear the system kick in on a more or less regular basis. It may come on a little more frequently or stay on when it is warm outside, since it never gets cold enough to relax the system, but on a cool day it operates like I remember.

[Kestas]

ksing, 40°F is pretty darn good for vent temperatures. You may want to but an inexpensive thermometer that looks like a meat thermometer. Put it in one of the vents and monitor the vent temperatures yourself during the weather fluctuations. It is also useful for proper adjustment of a refrigerator (0° in the freezer, 35° in the cold section, and 30-34° in the meat section). You may simply need to get used to your a/c this year. There's also a chance it may have been previously blowing at 35-38°F, and the difference is now noticable. Anyhow, the system was checked out and it seems the system is in good operating order.

[SHIFT_diesel]

My car was sold to me by a mechanic. He had to perform repairs on the car because its been in a accident. Either he knows that the condenser was hit and broken, or he found out otherwise. Other than that, I wouldn't know whats wrong with it.

[wbrauer]

Since you've got pressure the problem is more apt to be elctrical. Various relays kick the compressor in and out etc. Sounds like dealer time if your mechanic was stumped.

[dmatre]

Is your car running with R12, or has it been updated to R134?

My '87 had terrible AC performance. Found that the previous owner had converted to R134.

A friend advised that on a 124, R12 blows 15-20 degrees cooler at the vents.

I converted back to R12, and the difference in performance was tremendous. In the summer, the fan always blew on high (with 134). After converting to R12, the fan blew at more normal speeds, and the car cooled quicker, and stayed cooler.

Just a thought . . .

[ksing44]

My 1995 E320 does use the newer, but not as good at cooling, R134 coolant. It worked fine until last year and I just haven’t been able to get it back to the way it was before the system was recharged. I am hoping the dealer can figure it out and that it may be a s simple as the independent mechanic just made some kind of mistake. I was hoping you guys would have a brilliant, but simple, recommendation to get my system back to cooool. [8D]

The temperature of the air coming from the vents is a little cool on a warm day, but the car never really gets cool inside. I noticed that the air is cooler if the fan is kept on low. As the fan speed increases, however, the temperature increases. It just seems that the cooling capacity of the system has been significantly diminished and that it can not keep pace with higher outside temperatures. This seems consistent with the coolant leaking out, but my mechanic told me the pressure is good. [?]

I was thinking that the system could have less than the required amount of R134, even if the pressure was good. I read something about having the system vacuum-dried and wondered what the symptoms would be, if moisture were allowed to remain in the system.[?]

[Kestas]

Moisture in the system won't affect vent temperature performance. It'll form acids and destroy the system over the long term.