MY AC doesn't blow cold or even cool on my 2000 Sonoma. It's been in the nineties and dog humid lately so I'm ready for some cool air. I bought 3 cans of R-134A and attempted to recharge it, no dice it won't take any. The compressor clutch pulls in and it runs, the interior blower runs, I even depressed the scrader valve breifly and a puff of refrigerant shot out. Oh yeah, yes I am sure I'm on the large suction line low pressure port. I tryed leaving the can in the sun to raise the pressure, still it won't go in. I don't get it, and ideas?????
No AC
- Thread starter pickemup
- Start date
Molson02536
New member
Below are normal car AC pressure readings with 134A.
Normal readings on high and low side with AC OFF (static pressure) – Depends on outside temperature, but normally is between 80-105 PSI
Normal low side reading with AC on high speed and MAX & engine at 800-1000 RPM’s – Ranges from 25-35 PSI
Normal high side reading ranges from 200-350 PSI
Don’t assume that if adding little Freon is good that adding a lot is better! Overcharging just a little can decrease the performance of the system and possibly damage the compressor.
With the AC on the coldest setting, use a thermometer in a middle vent. Normal vent temperature readings will vary depending on the (ambient) outside temp. The vent temperature should range from around 42-55 degrees in my experience. If normal gauge readings are obtained and the vent air is cold – STOP don’t overcharge the system.
The only proper way to remove refrigerant is with a AC recovery machine so if this is being done at home I can’t emphasize enough not to over charge the system. And actually the best way to insure the proper charge is in a system, is to use an AC machine to recover the R134a and then evacuate and recharge the system with the correct amount. Most cars have the specified amount on a decal under the hood. 3 Cans sound a bit to much, i think your system needs only 1-12 ounce can to recharge it.
Could be overcharged, not enough air going across condenser fins, compressor not pumping sufficiently… BOTH gauge readings are really needed to get a better idea. When I checking hold the engine at 2000 rpms, if the clutch on the A/C disengages. Then let the engine come back to idle, and if the clutch kicks back on. It does this constantly your system has a good chance of being over charged.
Here is a link that should help you recharge your system, but if think your system is to low on R134a that your compressor is not kicking on. Shake the can of R134a as your trying to charge the system, the gases in side the can will expand and positively charge your line but wear a glove to ensure you don't get frost burn from the can when it frost over.
Good luck and be safe and glad you got your engine running 100% again.
http://www.freeautomechanic.com/airconditioning.htmlHeres the deal, I do residential HVAC work. I do know how the system works generally. My compressor does not cycle on and off regardless of rpm, it stays engaged and compressor runs continuously. The vent temperature has no drop across the evaporator. I do own a set of manifold gauges for R-134A and an refrigerant recovery machine and a vacuum pump but have no adaptor for the hose ends so I was using the cheap plastic trigger adaptor for the cans. What I don't get is if you raise the pressure in the can by heat it should flow into the low side of the system, it does not. I've never ran into this before on a house or a car. I wonder if the cheap adaptor isn't depressing the scrader valve properly????
Molson02536
New member
Cool so we don't have to worry about over charging the system.
Best bet then is just to go and pick up the recharge line for the can to the Service port on the the accumulator at Auto Zone or Wal-Mart. Think that line is only $15.00 and has a gauge to it also for the DIY person, you most likely got the issue on had with the valve not being depressed. Just wondering if the temperature of your accumulator and and low pressure line is cold, making sure that your heater and A/C damper in your air ducts are not frozen. Bad vacuum line to your actuator doors in your air ducks may be causing you not to have any cold coming from your vent's.
Common for the vacuum line on the drivers fender where the vacuum canister will crack causing not enough vacuum for the actuator doors to fully open and close. Just a though, as you know too high or too low of R134a will cycle your A/C compressor and high and low readings to your Sonoma should be taken with the engine @2000 RPM with max setting and blower on high.
Keep me posted, be glad to know if it was just a simple adapter that's keeping you from recharging the system, the other thing that comes to mind would be a badly gunked up orifice tube and will need to be replaced.
Last edited:
Cool so we don't have to worry about over charging the system.
Just wondering if the temperature of your accumulator and and low pressure line is cold, making sure that your heater and A/C damper in your air ducts are not frozen. Bad vacuum line to your actuator doors in your air ducks may be causing you not to have any cold coming from your vent's.
Common for the vacuum line on the drivers fender where the vacuum canister will crack causing not enough vacuum for the actuator doors to fully open and close. Just a though, as you know too high or too low of R134a will cycle your A/C compressor and high and low readings to your Sonoma should be taken with the engine @2000 RPM with max setting and blower on high.
Keep me posted, be glad to know if it was just a simple adapter that's keeping you from recharging the system, the other thing that comes to mind would be a badly gunked up orifice tube and will need to be replaced.
Vent vacuum operated dampeners work fine. No low side suction line is not even cool much less cold to the touch when the compressor is running.
Molson02536
New member
High side hot or about the same as the low side???? Just doing this old school with you, without the gauges or readings
Both low and high side pressure lines feel the same, this indicates a cars AC system is low on refrigerant and is under-charged.When the compressor clutch is definitely engaged and the low side is high and the high side is low, the most likely cause is that the compressor is failing – it is not pumping sufficiently but we need a gauge to confirm this.
When the low side goes so low that it’s reading shows it is in a vacuum, the most likely cause is a bad expansion valve or blocked orifice tube. Another possibility is a restricted condenser. Blocked condensers are not as common as they used to be but if a compressor fails and comes apart inside the remnants can end up in the condenser causing it to restrict the flow of refrigerant. But i don't think this is the issue here since you mentioned that the service port is not taking any R134a, as mentioned you may need to break down and pick up the R134a recharge hose for the can you have and start with just the one can half a can at a time.
I had the same issues with my Wife's Montana last year going to Manhattan with the in laws. 5 people in that van and the A/C was then notice to be weaker that it usually is, guess having 5 people body heat plus the summer heat. Made a quick stop in to Auto Zone and picked up the can with a recharge hose and used just about 1/2 the 12 ounce can of R134a i bought by opening and closing the valve on the hose and letting the A/C cycle for 5min @2000 RPM each time rechecking the temperature coming from the vents and the system till today is still surprisingly cold.
Without the gauges, it can be done as long as you take you time and not to over charge as you well know in most cases that's worst, and in our GM product there more sensitive to pressure changes in the system.
High side hot or about the same as the low side???? Just doing this old school with you, without the gauges or readings
They are about the same temp. I will probably have to get a new adaptor. That seems the most likely to me. Not today though. Txs
New development: Today I went and purchased a new adaptor hose. Just for confirmation that it actually was depressing the scrader valve I hooked it up with no refrigerant can. Then I opened it "pulled the trigger breifly" and some refrigerant shot out, so it works. I checked several things: Engine off low side pressure was over 125 lbs. Next test I believe means even though the compressor runs it is bad: I started the engine and the suction pressure never dropped. 
I tryed purging some in case it was mega overcharged but still no change. One other weird thing: The vent temperature is 6 to 8 degrees above the surrounding ambient air temperature.
I tryed purging some in case it was mega overcharged but still no change. One other weird thing: The vent temperature is 6 to 8 degrees above the surrounding ambient air temperature.Molson02536
New member
New development: Today I went and purchased a new adaptor hose. Just for confirmation that it actually was depressing the scrader valve I hooked it up with no refrigerant can. Then I opened it "pulled the trigger breifly" and some refrigerant shot out, so it works. I checked several things: Engine off low side pressure was over 125 lbs. Next test I believe means even though the compressor runs it is bad: I started the engine and the suction pressure never dropped.
As mentioned above BOTH readings should be checked to have a better idea of what is going on with an AC system but based on the limited information.
1. Check the high and low gauge readings with the AC on & set on MAX/Recirculate, middle vents with the engine at 2,000 RPM’s, blower speed on high.
2. Check the vent temperatures with a thermometer from the middle vents, far right & far left vents?
3. What is the outside temperature at the time the readings were taken?
4. Check to see if the condenser fan blowing strong?
5. Notice if compressor clutch is cylcling excessively or not and in your case not.
The static gauge reading indicates that the system may be a little to high (indicating over-charged). The static reading can vary depending on the outside temperature also, just leave it be for now and see if you can get a hi and low reading for me. Here are the things to look for again to refresh our memories.
A. Both low and high side readings are lower than normal, this indicates a cars AC system is low on refrigerant and is under-charged.
B. If both low and high side readings are too high, this indicates an overcharged system – too much refrigerant. This also can indicate that the condenser fan is not working, is too slow or the car is overheating and heat is transferring from the radiator to the condenser.
C. When the low side goes so low that it’s reading shows it is in a vacuum, the most likely cause is a bad expansion valve or blocked orifice tube. Another possibility is a restricted condenser. Blocked condensers are not as common as they used to be but if a compressor fails and comes apart inside the remnants can end up in the condenser causing it to restrict the flow of refrigerant.
D. When the compressor clutch is definitely engaged and the low side is high and the high side is low, the most likely cause is that the compressor is failing – it is not pumping sufficiently. Rarely an AC clutch could be slipping but usually this will be accompanied with a squeal or chirp.
A/C normal readings for R134a:
1. Normal readings on high and low side with AC OFF (static pressure) – Depends on outside temperature, but normally is between 80-105 PSI
2. Normal low side reading with AC on high speed and MAX & engine at 800-1000 RPM’s – Ranges from 25-35 PSI
3. Normal high side reading ranges from 200-350 PSI
Keep me posted and keep up the great work.
With all thats been said being taken into account, putting the refigerant in with a robin air / equivalent makes all the difference in the world. I hope I am not preaching to the choir too hard.( not my intent) Taking the system down into a vacuum boils all the moisture out of the system.(kind of a big deal!) I have never really been a fan of the canned stuff, but I suppose it has its applications.
2 cents
2 cents