Thanks -- will do. Although my general plan is to avoid those circumstances that cause it not to work! I should have an opportunity sometime this afternoon or this evening to screw it up, so I'll check then and let you know.

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Anthracite 1980 300D -- 64k original miles with a new engine, on the road again!
Silver 300D -- second owner, Sunny's old baby, Ilse, 210 miles,
Having to thin the herd….
Silver 1983 300SD -- second owner, 325k miles
Gold 1981 300D -- well-traveled, solid little car
Beige 1984 300D -- 292k miles, grease machine, parting out
Seafoam green 1981 300SD -- 250k, windshield frame damage
too many assorted w123 & w126 cars, parts cars, and extras

Generally these systems are only equipped with a LOW pressure cutoff switch AFAIK, that is to prevent the compressor from running when all (or nearly all) of the refrigerant has leaked out...I don't think they have a high pressure switch but even if they did it would prevent the compressor from engaging...since you say it does engage I think you can rule this out as a theory anyway.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Sorry for being so long getting back on this, but I thought I should say there are "new" symptoms as the weather has gotten hotter, in case someone is following this thread for their own needs.

Now that it's hot, it naturally takes longer for the engine to cool. A couple of times, I've popped the hood to let it cool while I was in an appointment (talk about getting some strange looks!), and if there was enough time, I'd be cool on the next leg of my trip. If not, well... I'm grateful the car has good working windows!

The monovalve kit is in, and I've looked at both the instructions on the forum and the monovalve in the car. Looks like a cinch, and we woulda done it this weekend, except....I can't find our angle driver, and I can't get to those flat screws without it. It's just a tiny bit too far under the edge of the windshield.

DH has the car this week while I drive the newest addition to our stable and get a few things straightened out on her, so if he doesn't find our angled driver (or get frustrated and buys another one!), he'll run by our indy and ask him to do the switch-out during lunch one day this week.

I'll keep you posted on the results. I have great hopes that this is the solution to this particular issue with the AC, since the more I read about the monovalve, the more it explains my heating problems in the winter, as well.

Now, one more question -- the '84 we just bought has a fan that's twice as strong as either this '85 or our other '84. It's WONDERFUL! I've been through all the service records back to the original invoice (only 3 POs, the original owner didn't sell it until 2 1/2 years ago, and he was completely anal about repairs!), and I don't find any replacement of the blower motor. I'm going to re-check, but what would make the blower blow half as strongly on our other two? Switch (we still have two speeds -- slow, and slower), or what?

If anyone's got any thoughts, let me know. No hurry, but it would be cool (pun intended) to figure this one out and fix it.

__________________
Anthracite 1980 300D -- 64k original miles with a new engine, on the road again!
Silver 300D -- second owner, Sunny's old baby, Ilse, 210 miles,
Having to thin the herd….
Silver 1983 300SD -- second owner, 325k miles
Gold 1981 300D -- well-traveled, solid little car
Beige 1984 300D -- 292k miles, grease machine, parting out
Seafoam green 1981 300SD -- 250k, windshield frame damage
too many assorted w123 & w126 cars, parts cars, and extras

As a blower gets older and the bearings wear the friction goes up.. you may need new bearings...
Your blower may not be getting the electricity it needs due to a problem with the speed resistor... if you car has one... the type of motor used might require a resistor under normal circumstances to keep from overspeeding...unlike AC motors which where the speed is determined by the number of magnets and windings and the 60 cycle current... so reading the ohms on the high and low speed resistance wires may show a problem.
There are threads about putting in new bearings ...

Which fan are you talking about? In the dash or the radiator?

Cleaning coils lead to the solution to my recent cooling problems. The condenser coils in front of the radiator and the evaporator coils in your dash must both be clean for your system to work properly.

I posted about it here:
http://www.peachparts.com/shopforum/showthread.php?t=156006

Well, the monovalve went in last weekend, and made no difference in Ingrid's refusal to cool when the AC is turned on on a hot engine. I imagine the replacement will result in heat next winter, though, because that little ripple washer was squashed flat in the one we took out.

So it's on to other ideas. I'l review the thread and look to see what else I should check, abd watch for any new ideas that you guys may come up with.

As forthe new-to-us, '84 yet-to-be-named 300D with the wonderful blower motor (LOTS of cold air coming out of the side vents, even though it's got vacuum problems so the center doors are closed most of the time), today's project is removing the front door panels to replace the check straps. Hope it's as simple a project as everyone says it is. If so, I'll at least have a look at the in-door vacuum lines while I'm in there.

Thanks --

Sunny

__________________
Anthracite 1980 300D -- 64k original miles with a new engine, on the road again!
Silver 300D -- second owner, Sunny's old baby, Ilse, 210 miles,
Having to thin the herd….
Silver 1983 300SD -- second owner, 325k miles
Gold 1981 300D -- well-traveled, solid little car
Beige 1984 300D -- 292k miles, grease machine, parting out
Seafoam green 1981 300SD -- 250k, windshield frame damage
too many assorted w123 & w126 cars, parts cars, and extras

I just converted my 300D back to R-12. The difference is like night and day. Or should I say like summer and winter.

Sunnyintx
I had a problem much the same as yours. I bypassed the heater control valve and that solved the problem.

Phil

OK, I'll try anything once....

So how do you bypass the heater control valve? In fact, where is the heater control valve?? I'm not a mechanic, just a moderately competent tinkerer who can usually follow instructions.....

__________________
Anthracite 1980 300D -- 64k original miles with a new engine, on the road again!
Silver 300D -- second owner, Sunny's old baby, Ilse, 210 miles,
Having to thin the herd….
Silver 1983 300SD -- second owner, 325k miles
Gold 1981 300D -- well-traveled, solid little car
Beige 1984 300D -- 292k miles, grease machine, parting out
Seafoam green 1981 300SD -- 250k, windshield frame damage
too many assorted w123 & w126 cars, parts cars, and extras

if the insulation is missing, would that affect performance of the AC System?

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91 350SD
14 F150 Eco
19 Fusion Hybrid
11 GT500

Not significantly.

I need all the help I can get,....better get some foam wrap and tie wraps from the hardware store!
Thanks

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91 350SD
14 F150 Eco
19 Fusion Hybrid
11 GT500

Bypassing the valve should result in max heat all the time. (Unless you have a plug in the bypass line.) Are you sure you did not bypass the heater core instead?

I suspect that the insulation is there to prevent condensation on the pipe as much as to insulate. Pipe insulation should work fine.

Thanks.

Problaby will make the engine look a little nicer too. Now that I have a fresh coat of paint on her, engine is next, interior will be last!

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91 350SD
14 F150 Eco
19 Fusion Hybrid
11 GT500