just bought this truck last week, it was cool out, so when i turned the a/c on to try it out, it was just that..cool!......anyways, weather warmed up this week, turned it on, wasent gettin cold.....today i popped the hood...and boticed the front of the compressor is not turning with the a/c on....i checked a lil 10 amp fuse, it was good,..there is a bigger box looking fuse also.....where should my diagnosis begin, this boy must have air here in northwest arkansas in the summer!
1998 gmc sonoma a/c not working?
- Thread starter Frank G
- Start date
Molson02536
New member
A/C Class 101
To diagnose problems, an A/C manifold gauge set is needed to read high and low side pressure readings. Avoid adding refrigerant with a simple charging kit like the ones sold at parts stores. Don’t add any stop leak, this can cause problems in the compressor, expansion valve or condenser.
Using an A/C gauge set and seeing BOTH high and low side readings can help in diagnosing the problem when you know what to look for. First, on a 134A system the high and low side service ports are different sizes. AC gauge sets have color coded hoses, the blue color coded hose has a connection that fits on the low side service port and the red hose has a connection that will only fit onto the high side. The yellow hose won’t hook up to anything if just checking the readings; it can be used to connect to a vacuum pump or attached to a refrigerant can or tank.
Make sure the condenser fan comes on if there electric fans, (your Sonoma should have mechanical cooling fan) when the readings are being checked.
Below are normal car AC pressure readings with 134A.
1. Normal readings on high and low side with AC OFF (static pressure) – Depends on outside temperature, but normally is between 80-105 PSI
Note: less then 70 PSI will not active the compressor and system needs to be vacuumed out and recharged.
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
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.
1. Both low and high side readings are lower than normal, this indicates a cars AC system is low on refrigerant and is under-charged.
2. 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.
3. 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.
4. 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. Also be sure not to overlook the obvious, like a loose belt!
Knowing that the system is an enclosed system, there must me a leak somewhere that needs to be replaced. Common places are the O rings in the A/C compressor or the o rings to where the hose connects.
Other common things that can go wrong is the A/C high pressure switch being bad or the wire harness from the low pressure switch or the Compressor wire leads. So inspect all the wire leads, relays, and fuses. If all electrical components is on working order, chances are the system needs to be vacuumed out and recharged with R134A.
Here is a link that should help you trouble shoot your A/C problems. Good luck and feel free to keep us all posted.
http://www.freeautomechanic.com/airconditioning.html
To diagnose problems, an A/C manifold gauge set is needed to read high and low side pressure readings. Avoid adding refrigerant with a simple charging kit like the ones sold at parts stores. Don’t add any stop leak, this can cause problems in the compressor, expansion valve or condenser.
Using an A/C gauge set and seeing BOTH high and low side readings can help in diagnosing the problem when you know what to look for. First, on a 134A system the high and low side service ports are different sizes. AC gauge sets have color coded hoses, the blue color coded hose has a connection that fits on the low side service port and the red hose has a connection that will only fit onto the high side. The yellow hose won’t hook up to anything if just checking the readings; it can be used to connect to a vacuum pump or attached to a refrigerant can or tank.
Make sure the condenser fan comes on if there electric fans, (your Sonoma should have mechanical cooling fan) when the readings are being checked.
Below are normal car AC pressure readings with 134A.
1. Normal readings on high and low side with AC OFF (static pressure) – Depends on outside temperature, but normally is between 80-105 PSI
Note: less then 70 PSI will not active the compressor and system needs to be vacuumed out and recharged.
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
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.
1. Both low and high side readings are lower than normal, this indicates a cars AC system is low on refrigerant and is under-charged.
2. 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.
3. 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.
4. 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. Also be sure not to overlook the obvious, like a loose belt!
Knowing that the system is an enclosed system, there must me a leak somewhere that needs to be replaced. Common places are the O rings in the A/C compressor or the o rings to where the hose connects.
Other common things that can go wrong is the A/C high pressure switch being bad or the wire harness from the low pressure switch or the Compressor wire leads. So inspect all the wire leads, relays, and fuses. If all electrical components is on working order, chances are the system needs to be vacuumed out and recharged with R134A.
Here is a link that should help you trouble shoot your A/C problems. Good luck and feel free to keep us all posted.
http://www.freeautomechanic.com/airconditioning.html
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