A/c. Checking efficiency.

'94 E34 525i SE. Does anyone know the specific checking procedure for this model. I understand the procedure involves checking the inlet air temperature,
against the ambient air temperature, but I have no idea what the differential temperature should be. The a/c is working, but I feel it could, or should, be cooler. Bentley's is no help as it only deals with the mechanics of the a/c system. Maybe I'm expecting too much, so I'd like to check it myself before spending any money on having it checked by an a/c specialist. Anyone? TIA. Mike.
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On 7/3/2006 10:49 AM, Mike G went clickity-clack on the keyboard and produced this interesting bit of text:

I don't know any mechanic that checks the AC capability by doing anything other than sticking a thermometer into a vent and turning the AC and fan on full. Mine gets pretty darn cold, about 36 degrees F. There's no real magic to it. FWIW, I have a '94 E34 (530i). Yours should be pretty much the same. If it's not blowing cold, then it may be that you need the system recharged. If it's the first time it's been recharged, then you don't need to worry about leaks, but if it has to be recharged soon after, then you should get it checked out.
The top of the receiver/dryer unit has a little window on it. While the AC is running, you should see bubbles in the window. If you don't, then it's probably low on refrigerant and you'll have to take it in. I don't think R134a is available in stores like Freon was.
--
Baseball is ninety percent mental and the other half is physical. - Yogi
Berra

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Please check your procedure. Bubbles in the refrigerant means you're possibly low. Allow the system to run for at least 10 minutes and check the sight glass. If you see bubbles, add refrigerant until the bubbles just disappear. A sight glass that looks empty most likely is full of refrigerant. Otherwise the low pressure cutoff would have stopped the compressor from self-destructing. If you don't hear the compressor cycling, then most likely you're low of refrigerant.

system.
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On 7/3/2006 12:49 PM, John went clickity-clack on the keyboard and produced this interesting bit of text:

Thank you for the correction. It's been a while since I messed with AC myself, so I got it backwards.
--
A bather whose clothing was strewed
By breezes that left her quite nude,
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As I said in my post. The a/c seems to be working properly. But, as far as I can see, and Bentleys would appear to confirm it, the a/c system in my car doesn't have a sightglass. My Celica has one, so I know what to look for.
I know a thermometer in the outlet will show it's blowing cool air. I'm just wondering if it's as cool as it should be. My feeling is that it should be cooler. To be comfortable on a hot day, around 30C it has to be running at max. OTOH, admitted the a/c in my Celica is an R12 system which in general are more efficient, max on a hot day would give me goosebumps. Mike.
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My E34 was the same. No climate control on that - just off/on AC. My old Rover with a Delco AC system is much more powerful - but you notice the power it takes from the engine more.
--
*The sooner you fall behind, the more time you'll have to catch up *

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wrote:

What gas did your E34 use? AIUI, the changeover to R134a was around the early 90's. Is the Rover running on R12, or one of the so-called compatible refridgerants, or has it been converted to run on R134a?. R12 is a more efficient gas than R134a, so that could explain the difference. What's the latest on your top-up kit BTW? Might be something I'll consider using, if my system does prove to be down on performance. Mike.
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I have noticed that my E30 (a few years older than your car) converted to R134a runs about 25 degrees differential. When I press the switch to recirculate, the differential increases to almost 40 degrees. I am in Florida and this time of year it's nice to look down and see the thermometer that's hanging in the vent read around 45 when it's damn near 90 outside. BTW - All readings are in fahrenheit for those that are wondering :)
wrote:

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Thanks. That's the sort of info I'm after. 90 F is about the temperature we have in the south of england at the mo. Mine is a R134a system, but I very much doubt that I'm getting those sort of differentials. It gives me a guide of what might be possible if it's as efficient as it should be. Mike.
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snipped-for-privacy@lycos.co.uk says...

That's why you need to measure with a thermometer to see if it is as cool as it should be.
--
Peter Aitken

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Did you check the cabin filter for being dirty? Without proper air flow through the AC system, you won't get the cooling you should.

just
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Good suggestion, but the microfilter was changed about 6 months ago, when the car had a major service. I saw the old one removed and replaced with a new one, so I know for certain that it was changed. Seems no shortage of air. Anything higher than a fan setting of 2, and it's blowing a gale. :-) I'll see what a thermometer says before taking it any further. Mike.
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I believe that you've already checked that the aux electric cooling fan is working. One thing you could do is to get a big box fan (36" or so) and place it in front of the grill to see if that helps the heat transfer in the condenser. A/C shops do this to ensure that they've got enough airflow when testing the system's efficiency. In my BMWs, the air coming out of the a/c vents is about 10 degrees F cooler when the car is moving.
FloydR
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wrote

Oops!. Now I feel very foolish. The aux fan isn't working, and never has worked, since I bought the car over 2 years ago. It's not siezed solid, but it can only be turned with difficulty using a screwdriver through the grille.
Until you mentioned it, it had completely slipped my mind. But now you have, it's the most likely explanation for the a/c not getting as cool as I think it should.
One thing you could do is to get a big box fan (36" or so)

I picked up a good s/h fan last year, but hadn't fitted it, as it needed a new resistor as well. Which I now have, so I've no excuse for delaying it's fitment any longer. Even without the fan, the a/c does work reasonably well. Hopefully after fitting it, it will work even better.
Apologies if anyone thinks I've been wasting their time. Fortunately for me, I'm not always that stupid.
Mike.
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...

Well, there you go! Glad to have been of help.
FloydR
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It only makes a difference at slow speeds - say in town running.
--
*I get enough exercise just pushing my luck.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Mike G wrote:

If it's working properly and you'd like it colder, there is a product called ICE-32 which will do that. It is basically a synthetic lubricant for R-134a systems. You can install just like topping off refrigerant. It results in an immediate temp drop of 6 to 10 degrees every time. I have installed ICE-32 on a variety of vehicles, domestic and foreign, with immediate results. It also will quiet down a noisy compressor if it is not a failure noise. They make a variant for R22 home A/C. It works also, raising the heating temp (heat pump) last winter, and this summer the cooling temp is about 4 degrees lower than before. The only reason I haven't added it to my Z3 is it already freezes me out. But I'll do it just for reasons of longevity.
Check it out. they have a website.
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