So, after my wreck last fall I installed new condensor, drier, aux. fan, fan clutch (from a 602, used old fan [cheap]), new radiator. Flushed AC system per instructions found here, put in mineral oil in proper amount, pulled vacuum (not necessarily in this order) & popped in the proper amount of R-12 (re-convert from 134a). On edit: This is a '87 300DT.

The AC never cooled the car very well - lowest temps on 134a were around 60*F, even after a tech went over the system. The wreck took all that out, which was why I went with R-12.

Now, even with the R-12 the lowest temps from the vents are around 60*F. A home HVAC buddy of mine suggests that it might be the expansion valve needs changing. Does this sound like a possibility? All other parts except compressor are new. Advice/tips? Hate to tear into dash without some guidance.

If all the readers could know the year and make and model of your car. It is even nice to know what color it is.

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Junqueyardjim
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis



1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!

Yes, our mind reading abilities are very weak here. We also need to know the high and low side pressure and the ambient temperature at the time you read them.

nahh, figure at least the shop working on it is somewhat competent. so the pressures should be near ideal, I'm betting on a heat door flap mixing hot air into the cooling system.
he said 602 fan, so at least we know it's a 124... kindof know anyway.

Sorry 'bout that - I though the info was in my sig. But I see I don't have a sig anymore. Wrong settings?

It's a '87 300DT, 135K miles, green w/tinted windows (by PO), gets around 30 mpg on the highway.
There is no shop working on it, not yet at least. The thing about the guy that suggested the problem may be the expansion valve is a HVAC shop - home & commercial - not automotive. Like I said, before I tear into the dash I'd like a little guidance
as to whether this might be the problem. Thanks!

You need to hook up manifold gauges tot eh system to read out the pressures. Your HVAC buddy might have a set of gauges. Checking those pressures is the first step in diagnosing A/C problems. It could be a bad expansion valve, But I agree with vstech a blend door being in the wrong position seems more likely. especially since you are getting near the same temps from before you rebuilt the system.

If youu cant find gauges, try this:

have a friend hold the engine at around 2500 rpm with the A/C set to max cool. you stand over the motor and listen. If you hear the a/c compressor cycling on and off, chances are your pressures are good and the refrigerant side of the system is ok. You should hear a click about every 10-30 sec.

the compressor will only cycle if the vehicle is cool inside. if it's hot, and the system is pumping out hot air, the compressor will stay engaged.
another possibility is the compressor is not engaging at all.
more details are certainly needed to diagnose.

As VS indicates, this is not a pressure cycling system. The first step in troubleshooting this problem is getting pressures with a manifold set. Post the pressures along with the ambient temperature at the time.

I'll see what I can do about pressures, I have a set but one of the gauges is busted (might as well not have any, right?).

Went ahead & ordered expansion valve. I figured after 23 years changing it out wouldn't hurt. It was cheap enough...

Compressor IS engaging but not cycling. Can you futher explain the "flap" thing & where I can locate it?

What I really hate is loosing all my R-12. No one around here has recovery capabilities so I guess I'm screwed on that.

More when I have the info...

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1987 300DT
2002 Ford F-250 7.3 Crew Cab Short Bed

I think you need to search your area more thoroughly. In your climate SURELY someone still has a machine set up for R12!

Well, here where I live the closest AC shop is 65 miles away. There are three in that area. I have called, but they no longer deal with R-12 - just 134a. The few guys around here that used to do R12 gave it up years ago for 134a. None wanted to go to the trouble or expense of getting their 609 certificate. They've even gotten rid of their R-12 equipment .

See, I live on Hatteras Island, which is the easternmost point of land in North Carolina. We are surrounded by water and, until 1962 the only way to get here was by boat or airplane. The auto shops out here that even bother with auto AC only deal with R-134a.

I've been living out here for over 10 years & I can tell you with certainty that there are no R-12 shops here or within a reasonable drive. The closest would probably be in Norfolk, VA but that's a 6 hour drive round trip. For what it would cost me in fuel, I could probably afford the R-12 & do it myself .

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1987 300DT
2002 Ford F-250 7.3 Crew Cab Short Bed

Behind the dash is the heater box. It has a heater core and an evaporator and several doors that direct air flow. Heat comes from the heater core(duh) and cold comes from the evap. Depending on the temp you dial in and the temp reading from the interior temp sensor, the door moves to direct into the cabin from one or the other or both. If the door doesn't close all the way on the heat side then instead of full cold a/c your getting full cold plus a little heat.

I'm not real sure of the exact setup of the heater box in the 124's but if its like other MB's ive worked on, the expansion valve is a big job that should be avoided unless absolutely necessary. You may have to dissemble the dash some to fix an issue in the heater box, but at least you wont have to tear the whole box out of its mounting place.

Okay, I understand your situation now. I do NOT, however, understand a shop that says it takes too much time and expense to get a 609. It costs $15 and about an hour of time online. I don't want to take my car to anyone that lazy.

I will be heading out to the beach sometime soon, and I could take a look for you if ya wanted to meet me in like wilmington or so...
I found a recovery machine on craigslist for $25 and the small tank for another 15.00 so, that'd be a way to do your own recovery. feel free to PM me or post here, and I'll probably see it if you have questions about a/c.
do a search for 124 pod problems. I'm sure you will find PLENTY of reading on the subject.
my 87TD hopefully will not be giving me any issues for the foreseeable future on this, because I hear it's a serious pain to get at the pods that fail.

Vstech: Thanks for the offer, but Wilmington is about 270 miles from here. If you look at a NC roadmap, you'll see my problem getting from Buxton to Wilmington.

LB: Agreed, but that's what the economy has brought us out here. Everyone's on a shoestring, cutting the "fat" & right now R-12 is just "fat" since it's used very little now. Remember that this isn't the "big city" out here - we are far removed from what most of us are used to in auto repairs, etc. Not much help for us older car guys.

I don't thing the heater flap is the problem, since I'm not getting any heat out of the vents while in ECON mode. The pods that feed the footwells don't work, but other than that all functions are OK. When I change settings on the AC system, I can feel things changing behind the dash. As far as getting to the evap are concerned, my local Mercedes guy says it's no big deal on a 124, unlike earlier models. Guess he knows what he's talking about since he's been working on MBs for over 20 years as a dealer mechanic. He will do the install on the expansion valve, so it's his problem.

Thanks, guys. I'll see what happens when the expansion valve gets here next week & I get it installed. Will report back. Any other ideas?

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1987 300DT
2002 Ford F-250 7.3 Crew Cab Short Bed