Is A/C working normally?

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Tnplumber

Tnplumber

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I ran my A/C today in my 72 Dart. The system is bone stock except someone converted it to 134a at some point. It was done by an A/C shop. The outside temp was in the mid 90s and with the car cruising at 60 mph the air coming out of the vents was about 52 degrees. I would like to see it cooler. What should I expect?
 
The AC in my work van blows 60 degrees at the vents and it keeps the van cool. I would think at 52 degrees it should be sufficient to cool your car. However on 90 degree days the AC in my truck is laboring to cool the interior
 
If ambient temp is 90 and you're getting 52° air out of the vents, that's a ∂T of 38 degrees, which is really excellent. The reason it doesn't seem good enough is your A/C is fighting a losing battle with the sun, which is making your car into a solar oven. You will find even a well-engineered and properly-selected and -installed A/C system will have a very difficult time cooling a steel box in the sun unless you give it a fighting chance by keeping some of the heat out. Step number one: thoughtfully pick a good variety of window tint film—not the cheap grey/purple junk; see my comments here—and have it applied. You'll also want to take down the headliner and apply some good insulation to the underside of the roof.
 
Geezus Kareiaust. You don't figure delta T based on INDOOR discharge temp and OUTDOOR ambient. You figure it based on the DIFFERENCE between what is ENTERING the evap and what is LEAVING the evap.

But this sounds like a conversion from R12- to ?? is that right? Some of these conversions reduce efficiency, because the components are not optimized for the new refrigerants. R-12, unfortunately, was a VERY efficient refrigerant for certain things.
 
67Dart273 said:
Geezus Kareiaust. You don't figure delta T based on INDOOR discharge temp and OUTDOOR ambient. You figure it based on the DIFFERENCE between what is ENTERING the evap and what is LEAVING the evap.
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Yes, that's right. And the air entering the evaporator comes from…

…class? Anyone? Buehler?

From outside via a very short path. It's drawn in through the cowl air intake between the base of the windshield and the aft edge of the hood, down and in through the passenger-side dash pass-through, and from there directly into the evaporator coil. That's in every mode except "MAX A/C", in which the air is recirculated within the vehicle rather than drawn from outside. If one is following proper factory-specified system performance test protocol, one does not use "MAX A/C" for ∂T tests.

This is the '65-'72 A-body system we're talking about; try and keep up, willya? ;-)
 
slantsixdan said:
Yes, that's right. And the air entering the evaporator comes from…

…class? Anyone? Buehler?

From outside via a very short path. It's drawn in through the cowl air intake between the base of the windshield and the aft edge of the hood, down and in through the passenger-side dash pass-through, and from there directly into the evaporator coil. That's in every mode except "MAX A/C", in which the air is recirculated within the vehicle rather than drawn from outside. If one is following proper factory-specified system performance test protocol, one does not use "MAX A/C" for ∂T tests.

This is the '65-'72 A-body system we're talking about; try and keep up, willya? ;-)
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Ya know Dan you once insisted that I was on your ignore list. Wha?? happened? I'm getting pretty dammed tired of your snide remarks.

Please read the below, and "try and keep up"

(Right out of the shop manual which you can download from this site, and relative to the specific vehicle we are referring to)

Regardless of whether the factory didn't mention to run these tests in "max" or not, that is the ONLY way that any of them make sense. This would be the equivalent of trying to measure the cooling performance of your house unit with all the doors and windows open, either heating OR cooling.

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Outside doors are closed in "off" or "max AC"

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I've done A/C work for a long time. The general rule of thumb I've always heard is if you get 20* less than the ambient temperature blowing outta the vents, you're good to go. I would say you're deal is coolin it's *** off.
 
67Dart273 said:
Ya know Dan you once insisted that I was on your ignore list. Wha?? happened?
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I thought I'd give benefit of the doubt to your manners and had another look.

I'm getting pretty dammed tired of your snide remarks.
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Oh. I'm sorry you feel you're being forced to read them.

Please read the below
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It looks like a scan of the FSM which says exactly what I said it says: in all operating modes except MAX A/C, the air inlet is outside air. I can't imagine you're trying to claim I was wrong because the air inlet door is in the recirculating position not just in MAX A/C mode, but also in OFF mode; that'd be petty and ridiculous and I don't think you're either of those things.

Regardless of whether the factory didn't mention to run these tests in "max" or not
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That's, um, kind of a pivotal point.

This would be the equivalent of trying to measure the cooling performance of your house unit with all the doors and windows open,
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Not really, no. The house is not a good analogy for the car, because the house system always gets all its inlet air from within the house. There is no admittance of outside air. The car, on the other hand, not only uses outside air in most operating modes, but is also a great deal more susceptible to heating up by the sun than is the house. That's what makes (outside) ambient temperature so much more relevant when evaluating the performance of the car system than when looking at the house system.
 
I run a thermometer in the vent of my daily driver. If it's not in the low 40's, I'm not a happy camper. I'm not sure if you can get an old Mopar there, but I'm listenin' :wink:

I don't think a 20* split is even close to enough :scratch:
 
6pk2goDemon said:
I run a thermometer in the vent of my daily driver. If it's not in the low 40's, I'm not a happy camper. I'm not sure if you can get an old Mopar there, but I'm listenin' :wink:

I don't think a 20* split is even close to enough :scratch:
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Believe it or not, that's what's in most manufactures service manuals.
 
Ive worked on a lot of auto aircon although not too many old mopars.
BUT with pretty well everything else if you cant get under 50 degrees , it wont feel cool enough.
Ideally i look for 41 degrees .
Some cars just wont get to that .
But most in ideal conditions will cycle off at that and then back in about 50 degrees.
Retro fitted r-12 systems are not usually as efficient as they were with r-12.

Is the compressor cycling off at all?
Is the heater tap/flap closing off correctly?
check both these and let us know how you go

ben
 
In the field we generally accept 20 degrees below outside ambient temp as good however I have seen many systems go into the mid 40's on a hot day! Who would really want that for comfort though
 
My customers would laugh in my face if I told them that a 20 degree difference is good! lmao Especially when its 110 outside! I'm sorry but if the air blowing out of the dash vents is 90 degrees something is wrong!
 
BadAss71 said:
My customers would laugh in my face if I told them that a 20 degree difference is good! lmao Especially when its 110 outside! I'm sorry but if the air blowing out of the dash vents is 90 degrees something is wrong!
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When I lived down there in the AZ oven I converted a Ford Ranger over to 134. With the Spal fan turned off that was in front of the condensor I was lucky to see 55* on a hot day at idle, with it running I would see 35* or so. Just charged a neighbors truck, it was 70* ambient and 35* in the vent......

If I remember right on our house a/c (heat pump) 20* temp drop was outstanding.
 
The 20* temp drop from ambient is pretty much industry standard. If you get better, consider yourself lucky. When someone complains, that's the first thing dealerships around here do. If the system will cool down to 20* or more LESS than the outside ambient temp, you ain't gotta problem. Been doin A/C work since 1979 and that's how it's always been. If it's 100 out and the cabin temp is 80, cya later tater.
 
BadAss71 said:
My customers would laugh in my face if I told them that a 20 degree difference is good! lmao Especially when its 110 outside! I'm sorry but if the air blowing out of the dash vents is 90 degrees something is wrong!
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Yep, no doubt!! If the dash vents only blow 90* air here, you might as well open the windows and enjoy the breeze :razz: ;)

yellowdartdave said:
I get 33 to 35 deg out of my Mustang on a 100deg day.
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That's what I call great AC 8-) 8-)
 
StrokerScamp said:
I've done A/C work for a long time. The general rule of thumb I've always heard is if you get 20* less than the ambient temperature blowing outta the vents, you're good to go. I would say you're deal is coolin it's *** off.
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StrokerScamp said:
Sure. That's vent temperature, not cabin temperature. I'm talkin about ambient cabin temp.
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Not tryin' to start anything, but your 2 statements contradict each other. My original post in this thread said I needed a low 40's reading from a thermometer in the vent..........
 
6pk2goDemon said:
Not tryin' to start anything, but your 2 statements contradict each other. My original post in this thread said I needed a low 40's reading from a thermometer in the vent..........
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Yes....my first post there was when I was tired and had not slept in five straight days. Sorry bout that. The standard is cabin ambient temp 20 degrees cooler than outside ambient temp. ...and it does take vent temps in the 30s and 40s to do that on a hot day. Sorry bout that.
 
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