87 535 A/C not cooling good

E28 technical advice asked and given! Troubleshooting, modifications and more.
Post Reply
ronrickettsjr
Posts: 3
Joined: Dec 06, 2020 4:20 PM
Location: Alvord,TX

87 535 A/C not cooling good

Post by ronrickettsjr »

This was my grandmothers car,, It was bought New and was always a grocery getter. I was given the car when they didn't need to be driving. The A/C sounds like it oughta be blowing like a hurricane. But what actually comes out feels about half speed. Also it doesn't seem to feel that cool at idle and gets a little colder idled up. Love the car, it's a keeper. So my question is. Could it be bad heater valve, maybe a blend door. I'm open to anything at this point. This is my first Euro, it's all original 110k auto. Grandfather swapped out the metric wheels for some universals. Even has the original tool kit in trunk hatch with the micro fiber cloth. Gonna need paint though.

Thanks Ron
Mike W.
Posts: 26872
Joined: Feb 12, 2006 12:00 PM
Location: California Whine Country

Re: 87 535 A/C not cooling good

Post by Mike W. »

Welcome to the group!

Not a blend door, they don't have one. Heater valve is supposed to shut off with A/C on, but if it doesn't, you feet are likely to cook, but A/C will be unaffected. It's really two different systems. One caution is the middle slider, fresh air, all of them actually, should be off, all the way to the left. It's a full recirc system. That alone can make a significant difference.

Now I found a fully charged R12 system to work pretty well, but I seem to be in the minority. Even so it's not like a late model car. However most likely is it's low on charge after 34 years. One advantage over modern systems is it actually has a sight glass, which while not perfect, gives you a good indication of the charge.

If it is low, don't let someone talk you into a quick and dirty R134a retrofit. R134a at the very least needs a larger more modern condenser, it's a definite downgrade from stock if used as a drop in replacement.
Blue Shadow
Posts: 10195
Joined: Feb 12, 2006 12:00 PM
Location: SE PA

Re: 87 535 A/C not cooling good

Post by Blue Shadow »

The center slider would be what you might call a blend door control. It is electric on the 86 and up. It supplies air to the dash vents. Verify it closes when the slider is to the left, the recirc position and the one where these cars can have enough a/c power for a cool evening but not a Texas sunny afternoon with high humidity.

I suspect the door is open and you need a recharge. Mike is right, go R-12 unless you invest in a system upgrade to allow 134a to work as well.
ronrickettsjr
Posts: 3
Joined: Dec 06, 2020 4:20 PM
Location: Alvord,TX

Re: 87 535 A/C not cooling good

Post by ronrickettsjr »

Thanks for the advice, It's been converted over to 134. I suspected that might contribute to the problem but also the Texas heat. I will double check the charge and the slider door for proper operation. Also ya'll said all the control sliders should be to the left for proper A/C operation. Is that correct?
Also is there an after market condenser available for those?
Thank you Ron
tn535i
Posts: 5585
Joined: Jul 14, 2006 1:30 PM
Location: Middle Tennessee

Re: 87 535 A/C not cooling good

Post by tn535i »

Everything to the left puts the A/C in full recirculation, otherwise fresh air comes in some of the other areas with speed but not that much really. As stated two separate systems with two separate fans and only one or the other runs at a time.

If it were my car I would 'test' the system with R12a first. Easy DIY and works much better in these older cars designed for R12 than 134 can. I would see how well that works first making sure the compressor is good etc. R12a runs at lower pressures and requires much less gas by weight and it is very low cost by comparison to R12. Great for testing but huge debate over it being flammable. Our cars use very little gas in the first place so that risk while 'testing' is small.
Mike W.
Posts: 26872
Joined: Feb 12, 2006 12:00 PM
Location: California Whine Country

Re: 87 535 A/C not cooling good

Post by Mike W. »

tn535i wrote: Sep 06, 2021 12:13 PM Everything to the left puts the A/C in full recirculation, otherwise fresh air comes in some of the other areas with speed but not that much really. As stated two separate systems with two separate fans and only one or the other runs at a time.

If it were my car I would 'test' the system with R12a first. Easy DIY and works much better in these older cars designed for R12 than 134 can. I would see how well that works first making sure the compressor is good etc. R12a runs at lower pressures and requires much less gas by weight and it is very low cost by comparison to R12. Great for testing but huge debate over it being flammable. Our cars use very little gas in the first place so that risk while 'testing' is small.
Given that it's now R134a, that alone is reason for inadequate cooling, but it may very well have not been repaired and again low on charge.

Now I've no experience with either, but I'm hearing better reviews about air duster, R152a these days than the hydrocarbon refrigerants like R12a.
ronrickettsjr
Posts: 3
Joined: Dec 06, 2020 4:20 PM
Location: Alvord,TX

Re: 87 535 A/C not cooling good

Post by ronrickettsjr »

Thanks again, I figured when the old folks went to have it serviced at some point they were told how great and cheaper the 134 was in the long run. I'll get off into it and see what I find.

Thank you Ron
demetk
Posts: 8431
Joined: Aug 09, 2007 8:58 AM
Location: CT, USA

Re: 87 535 A/C not cooling good

Post by demetk »

R152 is much better than R134 and similar to R12 in performance plus it doesn't harm the planet. Plenty of conversion threads on the subject.
tn535i
Posts: 5585
Joined: Jul 14, 2006 1:30 PM
Location: Middle Tennessee

Re: 87 535 A/C not cooling good

Post by tn535i »

R12a does not harm anything which is why it is great for 'testing'. I think it also mixes well with any of the refrigerants and oils. The HC refrigerants are used in many other places with great success but taboo in the use. True safety issue or politics... IDK.

What really counts in these older cars is the high pressure you can make and balance with the low pressure across the existing expansion valve. It's complicated but if the pressure in the condenser isn't high enough, then the temperature made in the condenser won't be hot enough. What I mean is the refrigerant must get hotter than ambient air temp in order to give up heat from the system when it's 100+ outside. Thermodynamics rule the situation. So with 134a that pressure is much higher than your old compressor and x-valve was designed for. R152a is much closer to R12 and a good choice but R12a is actually lower even than R12. Meaning, a lower pressure will achieve high enough temperature in the condenser up front to extract the heat. So with a 30 year old potentially weak compressor and system the R152a or R12a might allow it to function well enough. Otherwise it should have a new compressor, parallel flow condenser, an x-valve and of course all new barrier hoses and seals to function properly in your high temp environment.

My 300k+ all original system in my 535 cools well on warm days but struggles when the temps creep into the 90's. Simple fact I don't have high enough pressure/temp up front to extract heat like a newer car. Second challenge is humidity here in TN, without enough btu's being removed I can't get the vent temp below the dew point. All the energy goes into condensing water and I'm lucky if I even get a few drips under the car. A modern A/C system will drip steadily here. i would think TX far less humidity and that should help you out.
Post Reply