A/C and fan issue
#1
09-07-2021, 12:08 PM
A/C and fan issue
1999 4WD LT.
Started the Blazer and the A/C was cycling on for a couple seconds then off for a couple seconds repeating on/off.
There is no air blowing out of ducts, don't hear or feel the fan running.
Turning the fan control off does not turn off the A/C.
Pushing the A/C button doesn't do anything.
Turned the vehicle off after about a minute didn't want to do any more damage.
Any advice welcomed, thank you for your help.
Started the Blazer and the A/C was cycling on for a couple seconds then off for a couple seconds repeating on/off.
There is no air blowing out of ducts, don't hear or feel the fan running.
Turning the fan control off does not turn off the A/C.
Pushing the A/C button doesn't do anything.
Turned the vehicle off after about a minute didn't want to do any more damage.
Any advice welcomed, thank you for your help.
#2
09-07-2021, 02:17 PM
Manual or automatic AC?
Do you have a digital voltmeter and know how to do circuit measurements?
While this cycling is going on is the accumulator cool and sweaty?
Do you have refrigerant gauges and know how to use them?
George
Do you have a digital voltmeter and know how to do circuit measurements?
While this cycling is going on is the accumulator cool and sweaty?
Do you have refrigerant gauges and know how to use them?
George
#3
09-07-2021, 03:05 PM
Hi, thank you for helping.
I went outside to check on what you asked for and upon startup the compressor was off. I was able to turn the fan on and then start the compressor.
The fan works, blows cold.
The accumulator got cold quickly, but it took about 5 minutes to begin sweating, is that ok?
I hooked up a refill system with gauge to the low side and got just under 45 psi. That is the top end of "filled" on my gauge.
The compressor did not cycle off on its own, it usually does that quickly on/off right? I had to push the a/c on/off button to get it to cycle off. Any ideas what that might be?
Your questions:
The A/C or heat does have an auto feature, one on the fan switch and on the face, feet, both, defrost dial. It is the left most counterclockwise position on the dials, about 7 o'clock.
I do have a digital voltmeter but you would have to be specific about exactly where I need to put it to give you a reading.
I didn't check it before and couldn't now but i doubt it would it was cycling crazy quickly. on/off/on/off etc.
I do not have refrigerant gauges like a pro would have, but I do have a refill gauge for the low side, used to have a leak that I got fixed.
Any additional questions or advice very much appreciated.
I went outside to check on what you asked for and upon startup the compressor was off. I was able to turn the fan on and then start the compressor.
The fan works, blows cold.
The accumulator got cold quickly, but it took about 5 minutes to begin sweating, is that ok?
I hooked up a refill system with gauge to the low side and got just under 45 psi. That is the top end of "filled" on my gauge.
The compressor did not cycle off on its own, it usually does that quickly on/off right? I had to push the a/c on/off button to get it to cycle off. Any ideas what that might be?
Your questions:
The A/C or heat does have an auto feature, one on the fan switch and on the face, feet, both, defrost dial. It is the left most counterclockwise position on the dials, about 7 o'clock.
I do have a digital voltmeter but you would have to be specific about exactly where I need to put it to give you a reading.
I didn't check it before and couldn't now but i doubt it would it was cycling crazy quickly. on/off/on/off etc.
I do not have refrigerant gauges like a pro would have, but I do have a refill gauge for the low side, used to have a leak that I got fixed.
Any additional questions or advice very much appreciated.
#4
09-07-2021, 04:05 PM
First on how the system operates:
Automotive HVAC systems have to operate in a massive range of operating conditions from sub zero weather up to 120F+ with the whole system is closed into a hot engine compartment. Because of that the pressures can vary widely and the system needs to be protected from the extremes of load and ambient conditions. Some systems have receivers and/or accumulators to guarantee liquid to the metering device and gas to the compressor respectively but there is a high pressure switch and a low pressure/cycling switch that shuts the compressor off if pressures go above the high limit (rare) or below the low pressure limit (happens a lot). When the system is first started in hot conditions the load on the evaporator is very high and the system runs continuously. As either the ambient conditions get cooler, the humidity gets lower and or the cabin gets cooler the load on the evaporator starts dropping, l pressures go down and the system may start cycling. Low refrigerant can also cause this but just adding more gas because your cycling is the wrong approach because you can overcharge a defective system that does not have a low charge problem. So, the compressor may cycle because its expected to under those conditions or because something is wrong. It is next to impossible to separate those two possibilities without a proper set of gauges, a meter and some knowledge. Someone with a high level of experience can guess pretty well by listening and feeling the pipes and hoses and measuring the vent temp in the cabin but a novice wont have that knowledge.
Your cold accumulator just tells me that your system is cooling which we needed when your fan was not running. The fact that you are inexperienced with electrical testing says that we probably cant successfully probe our way through your problems to find the cause but my best guess based on your earlier symptoms is a defective HVAC control module, its power or ground just based on dead buttons. Since you don't have much background in electrical maybe these can help along with searching for some you tube videos on using a multimeter:
https://blazerforum.com/forum/2nd-ge...59/#post732668
https://blazerforum.com/forum/2nd-ge...29/#post731395
George
Automotive HVAC systems have to operate in a massive range of operating conditions from sub zero weather up to 120F+ with the whole system is closed into a hot engine compartment. Because of that the pressures can vary widely and the system needs to be protected from the extremes of load and ambient conditions. Some systems have receivers and/or accumulators to guarantee liquid to the metering device and gas to the compressor respectively but there is a high pressure switch and a low pressure/cycling switch that shuts the compressor off if pressures go above the high limit (rare) or below the low pressure limit (happens a lot). When the system is first started in hot conditions the load on the evaporator is very high and the system runs continuously. As either the ambient conditions get cooler, the humidity gets lower and or the cabin gets cooler the load on the evaporator starts dropping, l pressures go down and the system may start cycling. Low refrigerant can also cause this but just adding more gas because your cycling is the wrong approach because you can overcharge a defective system that does not have a low charge problem. So, the compressor may cycle because its expected to under those conditions or because something is wrong. It is next to impossible to separate those two possibilities without a proper set of gauges, a meter and some knowledge. Someone with a high level of experience can guess pretty well by listening and feeling the pipes and hoses and measuring the vent temp in the cabin but a novice wont have that knowledge.
Your cold accumulator just tells me that your system is cooling which we needed when your fan was not running. The fact that you are inexperienced with electrical testing says that we probably cant successfully probe our way through your problems to find the cause but my best guess based on your earlier symptoms is a defective HVAC control module, its power or ground just based on dead buttons. Since you don't have much background in electrical maybe these can help along with searching for some you tube videos on using a multimeter:
https://blazerforum.com/forum/2nd-ge...59/#post732668
https://blazerforum.com/forum/2nd-ge...29/#post731395
George
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