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AC failing to blow cold air

This is a discussion on AC failing to blow cold air within the General Help forums, part of the LSx Technical Help Section category; 98TA General AC question. AC failing to blow cold air, There are no leaks, it's fully charged, and the clutch ...

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    AC failing to blow cold air

    98TA
    General AC question.
    AC failing to blow cold air,
    There are no leaks, it's fully charged, and the clutch is activating fine. Any suggestions or other methods to test other components that would prevent this from working properly? Much appreciated!

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    Member senicalj4579's Avatar
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    when did u notce this happening? was it after a mod?

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    No mods since some headers installed last year but has worked fine since. Just noticed due to needing it for warmer weather and figured it just needed to be recharged but that didn't resolve it.

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    Member senicalj4579's Avatar
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    Quote Originally Posted by strikezilla
    No mods since some headers installed last year but has worked fine since. Just noticed due to needing it for warmer weather and figured it just needed to be recharged but that didn't resolve it.


    ok, have you looked into the compressor?

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    I checked it for leaks and checked pressure from day to day. Everything looked good. I can spin the clutch on it freely, and the clutch engages fine when on. That's the extent of testing I've done so far. Is there any other tests I can run to determine the compressor or another component failure?

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    Member senicalj4579's Avatar
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    i'm not really sure about testing on these things. i do hvac but not for auto;but its the same princible. what happens when you have it on? does it cool at least a little? because if everything seems to be operating and no cold air is coming out, i may assume that the compressor may not be getting the refrigerant hot enough to release enough heat at the condensor. was it not working before you recharged the system?

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    I have not used it in a few months and it worked fine then. When I tried to use it, all I got was warm air. After the full recharge the air temp is slightly cooler at best.

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    Member senicalj4579's Avatar
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    your sure theres no leak? did you do a actual pressure test?

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    yeah, nothing that I can see and the pressure tests results are consistent with 40psi from day to day.

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    Member senicalj4579's Avatar
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    i'm hopeing someone else who has more experience with auto a/c can tune in. i'm looking in my books right now to try to help you out. as of right now,my thoughts are that you will have to bring it in. i'm gonna continue looking for ya because i'm curious myself.

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    okay, much appreciated. I have a friend bringing me another compressor this week assuming it's the compressor like you mentioned, the compressor may not be getting the refrigerant hot enough to release enough heat at the condensor. I'll post the results if successful or if anyone else has any other ideas. Thanks again.

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    Check your AC belt.

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    Member senicalj4579's Avatar
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    i would suggest using a evacuation pump before recharging. also, try to do as much testing on it before you recharge the system. i'm reading it could also be more things

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    Member senicalj4579's Avatar
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    Quote Originally Posted by rbob93
    Check your AC belt.

    he said the clutch is working fine;indicating that the belt is fine.

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    You need to see what the high side pressure is-I'm assuming that 40 psi is the low side reading. That seems kind of high actually,unless it's really hot out.But you're saying it stays the same from day to day? I'm wondering if the high side reading isn't low and they are equalized (which would be a problem). You should run your A/C from time to time in the winter to circulate the oil,the defroster will do this,about once a month will help. I'm thinking you may have a blend door problem and the A/C is working ok-does the A/C lines get hot and cold? The compressor should cycle on and off also-does it just stay on? I need high and low side readings to diagnose this. Wanted to add that all A/C systems operate similarly,so the guy that does home A/C can help out some here ,but cars have different stuff like temperature control and a heater and stuff like that. Not a big deal,just a little different. Before spending the big bucks on a compressor,get it diagnosed properly,my garage does that for $29.99,plus freon.Tell them to leave it uncharged if you want to do the repairs yourself.

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    Member senicalj4579's Avatar
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    Quote Originally Posted by 02z28ls1
    You need to see what the high side pressure is-I'm assuming that 40 psi is the low side reading. That seems kind of high actually,unless it's really hot out.But you're saying it stays the same from day to day? I'm wondering if the high side reading isn't low and they are equalized (which would be a problem). You should run your A/C from time to time in the winter to circulate the oil,the defroster will do this,about once a month will help. I'm thinking you may have a blend door problem and the A/C is working ok-does the A/C lines get hot and cold? The compressor should cycle on and off also-does it just stay on? I need high and low side readings to diagnose this. Wanted to add that all A/C systems operate similarly,so the guy that does home A/C can help out some here ,but cars have different stuff like temperature control and a heater and stuff like that. Not a big deal,just a little different. Before spending the big bucks on a compressor,get it diagnosed properly,my garage does that for $29.99,plus freon.Tell them to leave it uncharged if you want to do the repairs yourself.


    exactly, i actually have a trouble shooting guide for auto that i was trying to help out with. i agree with you; even though my schooling,and tests did have auto,some things are similar but most of my experience comes from residential and commercial systems.

    the auto trouble shooter says to first check the accumulator pressure;sound familiour? thanks for the input

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    Senior Member 02z28ls1's Avatar
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    Well there's only going to be two ports on a car to check pressure at,they can be located at different places. One of them is smaller than the other on a 134A type system. The smaller one is going to be the low side,obviously the bigger one is the high side. I'm assuming that pressure reading was from the low side. Because it was working last time used,I'm leaning towards guessing it is low on a charge,and might have a leak. But I've recharged a lot of GM type systems and injected dye,and not had them come back with a problem. Presumably they just lost freon over time and needed recharging and they will be fine for a reasonable length of time. This is very different from home type A/C where most units still have the same charge in them 20-30 years later. Anyway-like I stated, need to have it properly diagnosed with both sides being read to know for certain whats going on.

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    Single Malt rbob93's Avatar
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    Quote Originally Posted by senicalj4579
    he said the clutch is working fine;indicating that the belt is fine.
    Not necessarily.

    But go ahead and have him re-build his entire system for a $15 belt that may be the original.


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    Junior Member jbigdawg79's Avatar
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    yes im having same problem if my air system is eliminated would that mess with my ac i charged mine also

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    on 1 wheel boobs's Avatar
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    overcharging a system can build to much pressure causing it to blow mildly cold air. check that first! Also could have a clogged orface tube building to much pressure. But like o2z28ls1 said we really need high and low side readings from it. Generaly your low should be in between 30-40 psi and the high around 200 280 psi. If it were me i would suck it down pull a good vaccumn on it then recharge it with the correct amount. some times having like half a pound more or less in a system can be the difference in 10-15 degrees

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