Times between AC cycles
Question:
I have a 90 gmc 1500 with 350.Lets say in second gear,so the rpms are up a little and going around 40-45,how often is the compressor suppose to cycle on and off?Thanks
Response:
Goes on and off depending on the inside temperature of your cab. If the cooling is in question, I suggest that you buy a small meat thermometer and insert into your middle vent to check the temperature. (mine stays between 40 and 45) if it reaches 60 (or more) and stays there, then you may have a problem. (I still don’t buy Exxon) robert brett slack *** ‘95 Cheyenne w/350, x-cab 190,000 miles, *** *** running like new (except for the seats). ***
I have a 90 gmc 1500 with 350.Lets say in second gear,so the rpms are up a little and going around 40-45,how often is the compressor suppose to cycle on and off?Thanks
Response:
Not only does your A/C cycle time vary with the inside temp in your cab, but also with the system coolant pressure which is measured by the A/C pressure cycling switch, which is located on the dryer – the silver cylindrical cannister next to the fire wall under the hood. If your system is low on freon, then it will cycle faster. Or if your core inside the truck is freezing up or the core in front of the radiator is blocked with bugs, road debris, or the fins are all bent over then the pressure builds quickly due to excessive heat and your system will cycle faster. It also depends on the amount of air moving thru the front core which allows it to bleed heat into the atmosphere and maintain proper operating pressures, as in when you are at highway speeds as compared to idling. Typically, you can count on an average of 15 to 30 seconds for cycling time, longer at highway speeds with plenty of air moving, assuming that your system is in otherwise good shape. I also understand that the newer systems have shorter cycle times, sometimes as low as 5 to 10 seconds at idle. If for whatever reason your system does not cycle off then your inside core will freeze (like mine did in my ‘95, but a new pressure cycling switch for $16 cured that). If you have quick cycling times or very short duration when the compressor does come on, especially on an older system, then the first thing I would do is have your system pressures checked and make sure that your front core is free of debris or bent-over fins so air can flow thru it. Good luck – Jonathan – Hide quoted text — Show quoted text – > Goes on and off depending on the inside temperature of your cab. > If the cooling is in question, I suggest that you buy a small meat > thermometer and insert into your middle vent to check the temperature. > (mine stays between 40 and 45) if it reaches 60 (or more) and stays there, > then you may have a problem. > (I still don’t buy Exxon) > robert brett slack > *** ‘95 Cheyenne w/350, x-cab 190,000 miles, *** > *** running like new (except for the seats). *** > I have a 90 gmc 1500 with 350.Lets say in second gear,so the rpms are up > a little and going around 40-45,how often is the compressor suppose to > cycle on and off?Thanks
– Acta Non Verba – Deeds Not Words Jonathan Race, Firefighter/Paramedic II Orange County (FL) Fire-Rescue Division A-Shift, Station 41 – "The Shark Tank" (http://home.mpinet.net/backdraft) Please follow directions in my return address, or Reply to: jrace at bitstorm dot net
Response:
Humidity is also a factor if you are using outside air, since humid air contains more heat stored in water. Therefore the a/c has to do more work to cool the air & condense out excess moisture so air at the duct may not be as cool. Roy – Hide quoted text — Show quoted text – > Not only does your A/C cycle time vary with the inside temp in your > cab, but also with the system coolant pressure which is measured by the > A/C pressure cycling switch, which is located on the dryer – the silver > cylindrical cannister next to the fire wall under the hood. If your > system is low on freon, then it will cycle faster. Or if your core > inside the truck is freezing up or the core in front of the radiator is > blocked with bugs, road debris, or the fins are all bent over then the > pressure builds quickly due to excessive heat and your system will cycle > faster. It also depends on the amount of air moving thru the front core > which allows it to bleed heat into the atmosphere and maintain proper > operating pressures, as in when you are at highway speeds as compared to > idling. > Typically, you can count on an average of 15 to 30 seconds for cycling > time, longer at highway speeds with plenty of air moving, assuming that > your system is in otherwise good shape. I also understand that the > newer systems have shorter cycle times, sometimes as low as 5 to 10 > seconds at idle. If for whatever reason your system does not cycle off > then your inside core will freeze (like mine did in my ‘95, but a new > pressure cycling switch for $16 cured that). If you have quick cycling > times or very short duration when the compressor does come on, > especially on an older system, then the first thing I would do is have > your system pressures checked and make sure that your front core is free > of debris or bent-over fins so air can flow thru it. > Good luck – Jonathan > Goes on and off depending on the inside temperature of your cab. > If the cooling is in question, I suggest that you buy a small meat > thermometer and insert into your middle vent to check the temperature. > (mine stays between 40 and 45) if it reaches 60 (or more) and stays there, > then you may have a problem. > (I still don’t buy Exxon) > robert brett slack > *** ‘95 Cheyenne w/350, x-cab 190,000 miles, *** > *** running like new (except for the seats). *** > I have a 90 gmc 1500 with 350.Lets say in second gear,so the rpms are up > a little and going around 40-45,how often is the compressor suppose to > cycle on and off?Thanks > — > Acta Non Verba – Deeds Not Words > Jonathan Race, Firefighter/Paramedic II > Orange County (FL) Fire-Rescue Division > A-Shift, Station 41 – "The Shark Tank" > (http://home.mpinet.net/backdraft) > Please follow directions in my return address, or > Reply to: jrace at bitstorm dot net
