A/C issues....
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Elder User
Joined: Jun 2006
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From: Gulfport/Biloxi, MS
A/C issues....
Last summer my ac seemed to work fine. This year as it starts to get warmer I notice it blowing cold only when I get on the gas pretty hard. If im idling the compressor doesn't seem to be on and the air is warm. As soon as I take off it normally comes on. I am assumeing that its low on freon, but im not sure. Would it being low cause the problem I am describing?
Postmaster
Joined: Mar 2001
Posts: 4,968
Likes: 3
From: So Cal
Could b e low on freon.
A quickie free test that MIGHT tell you if you are low, is to watch the AC compressor pulley while the AC is on at idle. You should see the pulley and the center disk spin and then not spin periodically. When the center disk is spinning the clutch is engaged and vice versa. If you don't see it engage, you might be low on freon which could be tripping the cutoff switch. When the cutoff is active it is telling the system you are too low on freon to run. reving the engine may fool the switch into thinking you have enough to run.
I am NOT an AC tech so the names I gave above are probably wrong but you will know what I mean when you look.
A better method is to bite the small bullet and buy yourself a recharge kit. Most of the decent ones have a pressure guage and good instructions that tell you how to tell if you are low and what to do about it. They are not very expensive and you will occasionally use it if you work on your own cars. I bought a fancy "deluxe" model last year and it cost something like $20. Usually one can of combined charge and lubricant is enough to top things up.
Don't buy a lot of cans of freon since it may take you years before you use them all up. I still have cans of the old R12? I bought back in the 80s, collectors items now from what I hear. Gonna have to buy me an old car with the old freon just for fun.
Jim Henderson
A quickie free test that MIGHT tell you if you are low, is to watch the AC compressor pulley while the AC is on at idle. You should see the pulley and the center disk spin and then not spin periodically. When the center disk is spinning the clutch is engaged and vice versa. If you don't see it engage, you might be low on freon which could be tripping the cutoff switch. When the cutoff is active it is telling the system you are too low on freon to run. reving the engine may fool the switch into thinking you have enough to run.
I am NOT an AC tech so the names I gave above are probably wrong but you will know what I mean when you look.
A better method is to bite the small bullet and buy yourself a recharge kit. Most of the decent ones have a pressure guage and good instructions that tell you how to tell if you are low and what to do about it. They are not very expensive and you will occasionally use it if you work on your own cars. I bought a fancy "deluxe" model last year and it cost something like $20. Usually one can of combined charge and lubricant is enough to top things up.
Don't buy a lot of cans of freon since it may take you years before you use them all up. I still have cans of the old R12? I bought back in the 80s, collectors items now from what I hear. Gonna have to buy me an old car with the old freon just for fun.
Jim Henderson
Thread Starter
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Elder User
Joined: Jun 2006
Posts: 764
Likes: 1
From: Gulfport/Biloxi, MS
Could b e low on freon.
A quickie free test that MIGHT tell you if you are low, is to watch the AC compressor pulley while the AC is on at idle. You should see the pulley and the center disk spin and then not spin periodically. When the center disk is spinning the clutch is engaged and vice versa. If you don't see it engage, you might be low on freon which could be tripping the cutoff switch. When the cutoff is active it is telling the system you are too low on freon to run. reving the engine may fool the switch into thinking you have enough to run.
I am NOT an AC tech so the names I gave above are probably wrong but you will know what I mean when you look.
A better method is to bite the small bullet and buy yourself a recharge kit. Most of the decent ones have a pressure guage and good instructions that tell you how to tell if you are low and what to do about it. They are not very expensive and you will occasionally use it if you work on your own cars. I bought a fancy "deluxe" model last year and it cost something like $20. Usually one can of combined charge and lubricant is enough to top things up.
Don't buy a lot of cans of freon since it may take you years before you use them all up. I still have cans of the old R12? I bought back in the 80s, collectors items now from what I hear. Gonna have to buy me an old car with the old freon just for fun.
Jim Henderson
A quickie free test that MIGHT tell you if you are low, is to watch the AC compressor pulley while the AC is on at idle. You should see the pulley and the center disk spin and then not spin periodically. When the center disk is spinning the clutch is engaged and vice versa. If you don't see it engage, you might be low on freon which could be tripping the cutoff switch. When the cutoff is active it is telling the system you are too low on freon to run. reving the engine may fool the switch into thinking you have enough to run.
I am NOT an AC tech so the names I gave above are probably wrong but you will know what I mean when you look.
A better method is to bite the small bullet and buy yourself a recharge kit. Most of the decent ones have a pressure guage and good instructions that tell you how to tell if you are low and what to do about it. They are not very expensive and you will occasionally use it if you work on your own cars. I bought a fancy "deluxe" model last year and it cost something like $20. Usually one can of combined charge and lubricant is enough to top things up.
Don't buy a lot of cans of freon since it may take you years before you use them all up. I still have cans of the old R12? I bought back in the 80s, collectors items now from what I hear. Gonna have to buy me an old car with the old freon just for fun.
Jim Henderson
More Turbo
Joined: Aug 2006
Posts: 530
Likes: 2
From: W. Wisc
Skip the DIY crap kits. But it sounds like you know that.
My guess would be one of three things - and note, it is only a guess based on incomplete info.
To figure this out you need to get a set of AC gages on it and report back. Key data required are: High side pressure, Low side pressure, Compressor Clutch time on, Compressor clutch time off. It is best to do this a bit above idle with gas engines so it helps to have a helper to read gages - not sure on diesels, but probably similar. You also really need ambient temps to be about 70 or greater for a decent read on things.
Now my guesses:
1. Clutch gap too big due to wear. Check it and it typically should spec in between 0.016" and 0.030". Check the gap between the part that sits still when the clutch is off and when it's on. Hard to describe, easy to show. Check in a couple spots and average. If this is it, you just need to pull the clutch and remove a thin shim (thin washer) to get it back in spec.
2. Compressor is toast (or nearly so). Gage readings will confirm/refute this. Major pain.
3. Low on Freon. If so, you will often see a fast clutch cycle - like only 2-5 sec on then off for a bit. If it is low that means you have a leak. Welcome to hell (finding it). Major pain, or just refill it every so often, if you hate ozone.
If you have access to freon recovery equip, then you should have access to gages. Use them and report back. On an R134a system, they are foolproof to use as the 2 ports are very different sizes. Put a rag around the ports when attaching/removing the fittings so you don't blast freon everywhere (especially important if you or someone else has used UV tracer dye!!!). If you also have access to a freon sniffer, then you might be able to find a leak if it is the case. Check every joint in the system, and especially around all compressor moving parts.
There are other potential sources, but they are increasingly rare. My first money would be on clutch gap.
Hope this helps, but you need to get gages on it to really diagnose. No substitute.
-Dave
My guess would be one of three things - and note, it is only a guess based on incomplete info.
To figure this out you need to get a set of AC gages on it and report back. Key data required are: High side pressure, Low side pressure, Compressor Clutch time on, Compressor clutch time off. It is best to do this a bit above idle with gas engines so it helps to have a helper to read gages - not sure on diesels, but probably similar. You also really need ambient temps to be about 70 or greater for a decent read on things.
Now my guesses:
1. Clutch gap too big due to wear. Check it and it typically should spec in between 0.016" and 0.030". Check the gap between the part that sits still when the clutch is off and when it's on. Hard to describe, easy to show. Check in a couple spots and average. If this is it, you just need to pull the clutch and remove a thin shim (thin washer) to get it back in spec.
2. Compressor is toast (or nearly so). Gage readings will confirm/refute this. Major pain.
3. Low on Freon. If so, you will often see a fast clutch cycle - like only 2-5 sec on then off for a bit. If it is low that means you have a leak. Welcome to hell (finding it). Major pain, or just refill it every so often, if you hate ozone.
If you have access to freon recovery equip, then you should have access to gages. Use them and report back. On an R134a system, they are foolproof to use as the 2 ports are very different sizes. Put a rag around the ports when attaching/removing the fittings so you don't blast freon everywhere (especially important if you or someone else has used UV tracer dye!!!). If you also have access to a freon sniffer, then you might be able to find a leak if it is the case. Check every joint in the system, and especially around all compressor moving parts.
There are other potential sources, but they are increasingly rare. My first money would be on clutch gap.
Hope this helps, but you need to get gages on it to really diagnose. No substitute.
-Dave
Thanks Riggz! I try to help...
Posting Guru
Joined: Apr 2004
Posts: 1,342
Likes: 0
From: Georgia
Last summer my ac seemed to work fine. This year as it starts to get warmer I notice it blowing cold only when I get on the gas pretty hard. If im idling the compressor doesn't seem to be on and the air is warm. As soon as I take off it normally comes on. I am assumeing that its low on freon, but im not sure. Would it being low cause the problem I am describing?
Ambient temp Low side psi High side psi
85* 45-55* 225-250*
90* 45-55* 250-270*
95* 50-55* 275-300*
100* 50-55* 315-325*
Using the chart and checking with a good gage (not the el cheapo), :
1) If low side is low and high side is low- add 1 can.
2) If low side is low and high side is high-usually blockage in the system like expansion valve or orafice tube.
3) If low side is high and high side is low-usually faulty valve in compressor (gages usually go nuts when this happens)
4) If low side is high and high side is high-overcharged system also resulting in a not so cold a/c. hope this helps your diagnosis. <!-- / message --><!-- sig -->
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