Deciphering AC vent temperatures

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Originally Posted By: JHZR2
Well I wasnt cruising in any of these situations, just driving around town, the cars were fairly heat-soaked, etc.

The VW was more than comfortable with its temperature. Not quite 40F drop, but over 30. Never touched the system, and Im not sure I care to try to add 134a, would rather leave it closed. Its comfortable.

We never run on recirc for the most part... I dont think it works on my 318i, and I dont have an option on the 240D.

I think it all is what it is, other than the 240, which will get some R12.


JHZR2, I had a BMW before. E30. Could it be that we just can't figure out those funky HVAC controls, and we just THINK we got the air on, if we press the Snowflake?
lol.gif


No experience with M-B Mercedes Benz if thats still censored - ok good, the abbreviation for Mercedes-Benz is no longer censored.

I think the AC works no matter how hot the car sheet metal gets, or how "heat saturated" it is. Of course, if car's fan clutch wasnt working right, yeah it would overheat..
 
Originally Posted By: TechnoLoGs
Originally Posted By: JHZR2

We never run on recirc for the most part... I dont think it works on my 318i, and I dont have an option on the 240D.

I think it all is what it is, other than the 240, which will get some R12.


JHZR2, I had a BMW before. E30. Could it be that we just can't figure out those funky HVAC controls, and we just THINK we got the air on, if we press the Snowflake?
lol.gif


No experience with M-B Mercedes Benz if thats still censored - ok good, the abbreviation for Mercedes-Benz is no longer censored.

I think the AC works no matter how hot the car sheet metal gets, or how "heat saturated" it is. Of course, if car's fan clutch wasnt working right, yeah it would overheat..


The BMW has a recirc button. It has never done anything that I can notice. The car was a flood car, and it is probably the one thing on it that does not work. Everything else on the car has been fine for >75k and 10 years.

The mercedes just does not have one... Simple as that.
 
Originally Posted By: Chris142
Generally anything in the 40's or less is aceptable. Your 60's temps are not.

Here is my 87 f250 that I retrofitted to R134a. Outside temp in the shade.




And Fords are known to have very large condensers. Two of the cars I own and are in this situation are known to have barely good enough (by whose standards I dont know) AC when running the right fluid, let alone anything off design. R134a is known to reduce performance, and this isnt my first retrofit euro car (318), so it is sort of a matter of course. If I would retrofit parallel flow condensers and more refrigerant capacity, Im sure the temps would go down. My pressures are fine, I know there is no air in the systems, etc.

Our VW may not have acceptable temps according to whatever logic you use, which Im not questioning, but it has always blown this way, and Id say it is quite comfortable.

Not sure my tests are done right either
smile.gif


Given your experience, what should I go after? I know the following:
-all compressors work
-no belts slip
-cycling occurs on the VW and BMW
-pressures when operating are fine for R134a thermodymics

I go off of a general 134a T-P chart,for high and low side. Ive never touched the VW or added any.

So what should I go after???

Thanks!
 
IMO the bmw and benz were barely adequate when new. The benz should have a sight glass so checking the r12 charge should be easy. The BMW being a retrofit will need a complete evac and recharge to 85% of the r12 charge and only then can you get accurate readings.

My friend thats selling the kits to put a sanden on the benz cars has put a paralel flow condenser on a couple and that made a huge improvement.
 
You don't really want it much lower than 40F; here's why:

Once I owned a '78 Chrysler Cordoba, whose TXV failed. A good AC shop converted it to cycle, and put an external TXV on it that cycled the clutch. I thought I wanted it really cold, so I bought a tiny wrench and cranked the adjuster to make 'er really cold. I'd start the car and drive onto the freeway in 100F summer with the AC on full blower, fresh air. About 10 minutes later airflow stalled because the evaporator core iced up solid. I turned the compressor off, then 5 minutes later I'm being hit in the face with ice particles. So, too low a setpoint means you'll ice the evaporator core.

Also, measure the temps at all the vents. You may notice one side of the car is a lot warmer than the other. If your system is marginal for some reason there may not be enough refrigerant boiling off in the evaporator and you may have part of the evaporator cooling a lot and part not really dropping the temp much at all.
 
Quote:
We never run on recirc for the most part... I dont think it works on my 318i, and I dont have an option on the 240D.

If there is no discrete control for recirculation, it might be part of so called "Max AC". Domestic used to do that.

You will have problems if you can not keep on the recirc. Most systems are designed to to handle recirc air. They just don't have enough oomph to cool in the fresh hot air all the time.
 
what Vikas said......our '98 Cherokee doesn't cool at all well when bringing in fresh air but cools extremely well on recirculation (1st position on ac control). I just checked the vent temps on it after reading Vikas' response....the garage is 84'f and on fresh air setting, idling, the vent temps are 59'f and on recirc at the 3 minute mark are 44'f.
 
Originally Posted By: JHZR2
Originally Posted By: TechnoLoGs
Originally Posted By: JHZR2

We never run on recirc for the most part... I dont think it works on my 318i, and I dont have an option on the 240D.

I think it all is what it is, other than the 240, which will get some R12.


JHZR2, I had a BMW before. E30. Could it be that we just can't figure out those funky HVAC controls, and we just THINK we got the air on, if we press the Snowflake?
lol.gif


No experience with M-B Mercedes Benz if thats still censored - ok good, the abbreviation for Mercedes-Benz is no longer censored.

I think the AC works no matter how hot the car sheet metal gets, or how "heat saturated" it is. Of course, if car's fan clutch wasnt working right, yeah it would overheat..


The BMW has a recirc button. It has never done anything that I can notice. The car was a flood car, and it is probably the one thing on it that does not work. Everything else on the car has been fine for >75k and 10 years.

The mercedes just does not have one... Simple as that.


Ahh, so you don't have this indecipherable thing from an E30 then (1984-1991 or 1992 if a convertible).
smile.gif


2965-5725-1-lb.jpg
 
Reason Fords perform so well is most folks will use MAX which is recirculation and is the only setting I use, EVER... Last thing I want in my car is humidity and/or diesel fumes from traffic or from traveling through one of the many tunnels around here...
 
Originally Posted By: OVERKILL
How in the heck is that indecipherable?


Can YOU Decipher it? I can't.

If so, can you enlighten?

It's.. Why, well its German to me. Seriously.

*Unless... UNLESS.. I thought about it: Unless there were THREE separate fans, ALL of which blew their OWN direction. For example: On face, then up, then down. And EACh one had a "speed control," as per slider. Other than that.. Well, then add the fan speed, and snowflake.. NO Sense!!!

When I had mine, I just turned everything all the way up and it kinda mostly got real cold. Never did know what I was doing.

Not everyone a ssmart as you, OVERKILL.
 
Originally Posted By: TechnoLoGs
Originally Posted By: OVERKILL
How in the heck is that indecipherable?


Can YOU Decipher it? I can't.

If so, can you enlighten?

It's.. Why, well its German to me. Seriously.


What part are you finding confusing? I'm not having an issue with it.... 0 is off. The image on the other side of the slider is the function controlled by the slider. You increase output to that area by moving the slider toward it. It is pretty simple
21.gif


EDIT: Saw your edit. Fan control is separate. The sliders control traps that manipulate how much/how little air passes through that vent section. This allows you to fine-tune airflow to each section, whilst manipulating the fan speed with the dial.
 
Originally Posted By: TFB1
Reason Fords perform so well is most folks will use MAX which is recirculation and is the only setting I use, EVER... Last thing I want in my car is humidity and/or diesel fumes from traffic or from traveling through one of the many tunnels around here...



In my F150 I use recirculate rarely. On the hottest most humid day here it will freeze you out.

It has been my experience (owed many domestic and imports) is that Ford and especially GM AC is always stronger (blows stronger and colder). Was presently surprised with the AC in my Challenger, much better then the Magnum before it, gets so cold your eyes start to water if your not careful, may be better then the F150
 
Originally Posted By: OVERKILL
How in the heck is that indecipherable?


Exactly. High, middle and low airflow controls, then an AC button (snowflake) and a recirc button (circular arrows). Most simple.

If you need help deciphering buttons in a car, start a new thread, not needed here.
 
Originally Posted By: Vikas
Quote:
We never run on recirc for the most part... I dont think it works on my 318i, and I dont have an option on the 240D.

If there is no discrete control for recirculation, it might be part of so called "Max AC". Domestic used to do that.

You will have problems if you can not keep on the recirc. Most systems are designed to to handle recirc air. They just don't have enough oomph to cool in the fresh hot air all the time.


Fortunately we are more than comfortable running with fresh air in most all the time. Even in 2 of the 3 cars here, all of which have possibly unacceptable vent temps.

Recirc works fine in the vw, we do t use it. Perhaps temps would drop into the 40s if I had set it. I dot feel a flow difference in my 318, making me think the function is broken. No option in the 240, it's a manual system, but no slider, etc. I can't tell with the temp dial to 'min' that the flow changes, which seems to be an indicator of recirc. Maybe I'm wrong though...
 
To get comparable results, you really have to measure vent temperatures under the same conditions. Most service manuals include setting the system to recirculation mode and letting the engine idle for a few minutes with the HVAC fan on high, and then taking the temperaure. The service manuals for our Honda, for example, gives a graph that shows acceptable vent temperatures for any given ambient temperature AND relative humidity.

Acceptable vent temperatures are anywhere from 36-42 deg F for ambients in the upper 60s, to 62 deg F for an ambient of 105 with 30% relative humidity (which would be a dewpoint nearing 70, which is very high for that ambient temperature).
 
I don't know about the 240D but VW and I am pretty sure BMW as well do not cycling the A/C Compressors, they are variable displacement. They are either on all the time without a clutch(some are) or stay on once commanded by the ECU.

http://www.polarbearinc.com/Articles/Variable Displacement Compressor.pdf

013_compressorWobblePlate.jpg


The BMW is more than likely just a poor retrofit system for 134a, some are, some aren't. They do sell a new compressor for 134a. The clutch fan could be giving up. Some are lazy without being outright bad.
 
Both the 240 and the 318 have clutches and they cycle.

A new compressor for 134a is fairly ridiculous, if you take out the old mineral oil (not miscible in 134a) with a solvent and then add the right lube. I put in a new compressor as the bearings on the old one were getting loud. There isnt a fundamental difference between, say, an R4 sold "for 134a" and an R4 that was used with R12.

As I said, the air coming from the car is quite comfortable, the system has not leaked and is going on 10 years now, so I cant say that its really a bad retrofit. Even if the temps are theoretically a bit high.

A new condenser would be the right mod if going to 134a from R12. But in older vehicles like my 240D (30 years old), I dont cre to stress the system with higher head pressures.
 
Originally Posted By: Hokiefyd

Acceptable vent temperatures are anywhere from 36-42 deg F for ambients in the upper 60s, to 62 deg F for an ambient of 105 with 30% relative humidity (which would be a dewpoint nearing 70, which is very high for that ambient temperature).


Interesting... So for conditions like 86F with 57% humidity, my numbers are likely not all that bad... let alone when it was 94 with 50+% humidity.
 
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