I have spent around $1500 on my A/C and it STILL won't cool. This is on my 1985 300 TD Turbodiesel. One problem seems to be a leak. I replaced the unspeakeably expensive front hose (the one with the valve on it) because the shop told me that the valve was damaged, and had it recharged with R-12. This gave me about a month of cool. I had it converted to R-134a after many assurances that this was the wise thing to do, and according to the mechanic, several leaks were found, the dryer was replaced, and another $900 was removed from my wallet. The shop told me that they were absolutely, positively sure that the only remaining problem was the aux. cooling fan, the one in front of the radiator. Only another $425. After some searching, I found another on E-bay and replaced it myself. It would not turn. I hooked it up with some test leads and it blew like mad. So did the old one, after a shot or too of penetrating oil.

I was then told by a fellow in the parts shop who has an '82 300D that the five-pin aluminum 'ice cube' relay could be the problem. I went to the U-pick junkyard and got two of these, and still it won't blow. I tried connecting the two leads to the climate switch. This makes something (I think the compressor) click, as does plugging in the leads, so I am assuming that the switch on the dryer is okay. I don't see bubbles in the sight glass. I have been told that with r134a, I should see bubbles, so there is probably another leak. The shop guy said that dye was used and that this rarely fails to find all the leaks.

I told the shop guy about his misdiagnosis, and he said to bring it back and he'd spend some free time on it. But I am most interested in having a cool car. What could be the problem? There is also a large black relay-looking device, labeled "Klima", but the parts guy said that these control the compressor. A new one would be very expensive, and there were none I could find at the U-pick yard, though I could look again, they have a pretty fast turnover.

Whatever could be the problem here? I will greatly appreciate any help with this.
I am not ruling out that something was installed incorrectly at the shop.

So I figure that there are two problems: a leak and a fan problem.

The leakage rate is about the same as when I first brought the car to the shop in March of 2006.

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Semibodacious Transmogrifications a Specialty

1990 300D 2.5 Turbo sedan 171K (Rudolf)
1985 300D Turbo TD Wagon 219K (Remuda)

"Time flies like and arrow, yet fruit flies like a banana"
---Marx (Groucho)

An inoperable aux. fan will not be the only cause for lack of cooling...if the system was otherwise working properly, with no aux. fan, you would still have good cooling especially at highway speeds where the aux. fan has no effect. What you would see with an inoperable aux fan, would be less cooling at idle and low speeds where you really need the aux. fan to move air across the condenser.

I have many questions about what was done.....

1) $900 to replace the receiver/drier ?....that is a $50 part and takes about a half hour to replace.

2) you only replaced the front hose? If all others are original, you are trying to make the ac work with 22 year old hoses....but more important, if you converted to 134, you need to have replaced all hoses with 134-compatiblae barrier hose, or else the thing will leak like a seive, not to mention that hoses likely leak anyway.

3) If you havent replaced hoses, than you are also using original o rings (neoprene) which are not compatible with 134. You need to replace with green o rings

4) You didn't mention anything about replacing the compressor....if you are using the original compressor, forget it, its just worn out and wont run the system, plus it probably leaks....

5) Flushing.....when you converted to 134 did they flush old mineral oil lubricant out?...this is absoulutely essential. Plus, you cant really flush an old compressor, so you may have old mineral oil in the system doing nasty things when reacting to 134.

6) Did they replace the expansion valve (located in passenger foot well)? If not, the system wont run properly.....its probably clogged with crud.

It sounds like your AC shop is taking your money without doing what is appropriate.

This AC system is really pretty simple, but there is only one way to rejuvenate a 20+ year old system, and that is to replace hoses, o rings, rec. drier, expansion valve and compressor, and flush all system components, before recharging with oil and refrigerant.

A few other comments: the AC systems in these cars is marginal at best....one of the real limiting factors is the relatively small size of the evaporator. These systems do work well with R-12, but when converting to 134, there are limitations. One thing you can do to improve fun ction is to replace with original condensor with a new universal type parallel flow condenser....this will require a little custom hose work (I put in one of these...18" tall and 22" wide.... and that improves cooling very much).

You cannot expect to fix an old AC system with a piecemeal approach....there are too many components that must function together...you really need to do a complete system rebuild. This does cost real money unless you do it yourself. AC shops are in a tough bind too, because too many customers just want to fix only what is broken, and just make the system work, and then hope all will be well thereafter, and it doesnt really work that way. Too often, when you only fix what is broken, the system will cool for a while until other components fail (hoses leak, compressors leak, exp. valve is clogged, etc. etc.)

Sorry about your trying experience....this is very frustrating..especially after such great expense!

Regards,

Mark

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

R-134A causes a roughly 30% efficiency loss over R-12, requires different refrigeration oil (preferably polyolester/POE, but polyalkaline glycol/PAG also works), all orings, dryer, expansion valve, a complete flush of the system, and a bigger condenser to have a chance of doing any good at all. If you suspect a leak, many auto parts stores (such as AutoZone) sell an easily insertable dye that can be seen with an ultraviolet light that indicates where the leak is and eliminates the "throwing parts at the problem" syndrome that is too common with the average A/C shop. I am a refrigeration tech by trade, and I can tell you that even among pros it can be difficult to locate leaks, my electronic freon leak detector doesn't pick up HFC refrigerants (such as R134) well at all, I personally use dye and pressurization with nitrogen to find leaks-if you do a search on this site, there are many alternative refrigerants that members have used to replace R-12. Good luck.

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1982 300DT 190K (Diesel Purge + synthetic oil=smoothness at last!!!)
2004 Ford E-350 6.0 L PSD 227K
2006 Dodge Ram 3500 SRW HO Cummins 4X4 48RE 42K (brute force tow vehicle)
2005 Scion xB wife's rolling pop can
1993 GMC Sierra C3500 6.2 142K

First of all, I'm not skilled in a/c work.

However, I can assure you that the situation with the auxiliary fan has nothing to do with the inability to cool, unless you are stuck in traffic with ambient temps above 90°F. That's the only point where the pressure in the system will climb sufficiently high to run the fan.

So, the inability to cool in every other situation is due to another problem.

But, with R-134A in the system (a bad decision), it's necessary to define "inability to cool".

Get yourself one of the vent temperature thermometers and insert it in one of the dash vents. See what the temperature is on a very hot day with the blower on low speed. The system may be working fine.........just incapable of giving the "cold" cabin that you desire. Report back with result.

The SD can just barely keep the cabin tolerable (nowhere near 70°F.) on a 100°F. ambient day. It's just inadequate with Freeze-12 (basically similar to R-134) with the limited condenser capability.

Others can point you toward the specific areas to check if the vent temps are unacceptably high.