AC clutch cycling on low fan setting.

[Tonys87]

Hi guys, I just finished redoing my AC.
In my 99 2 door Tahoe with no rear AC. I went with a Delphi compressor, ACdelco dryer, hoses and a rockauto condenser and a 4 seasons orifice tube. Everything went smooth..added 32 oz of Freon and it’s blowing really good. Only issue I am having is the compressor will sometimes cycle on and off but only at the lowest fan setting. Every other fan setting is fine.
Wondering if this is a known issue among the OBS trucks or do you guys have any suggestions?

FYI, I vacuumed down the system and it held vacuum for over 2 hours while I went out to dinner with the family. So I don’t believe I have a leak. Also only did 32oz because the old dryer had the info. Hopefully that is the correct amount. I will most likely go get a low pressure switch just in case that might be the issue.

 

[kennythewelder]

Sounds like it's low on freon. You need to hook up a set of gauges to it, and see what your pressure is doing. Not only while the system is running, but also with out the engine running. You need to look at everything. The high side will tell you the most info. Also the pressure when the system is at rest. All of this is dependent opon the ambient air temp, and even the humidity plays a factor.

 

[Tonys87]

Forgot to mention, the old AC delco compressor was also doing this at low fan speeds. One day the compressor just stopped working. So I figured I would replace everything at once. (Except evaporator) I also noticed the new compressor will cycle if I rev the engine up to 1500-2500 rpm’s at idle. I’ll take some notes down with the gauges but I honestly don’t know what to look for. I’ll figure this out. I don’t want to add more Freon till I’m 100 percent it need it.

 

[kennythewelder]

Forgot to mention, the old AC delco compressor was also doing this at low fan speeds. One day the compressor just stopped working. So I figured I would replace everything at once. (Except evaporator) I also noticed the new compressor will cycle if I rev the engine up to 1500-2500 rpm’s at idle. I’ll take some notes down with the gauges but I honestly don’t know what to look for. I’ll figure this out. I don’t want to add more Freon till I’m 100 percent it need it.

Yeah, it is imperative that the pressure is correct, for the AC to work rite. I have tried, and tried, and tried to do that work, without putting gauges on the system, and that just doesn't work. You must see all the pressure to get it rite

 

[kennythewelder]

Let me add this. It is the pressure switches, that let 12 volts go to the AC compressor. If the pressure switches don't have the correct pressure, the system will not come on. There is a low pressure switch, and I think 2 high pressure switches. One of which is located on the back of the compressor it self. If the pressure gets to high, the high pressure switch will open, and you have no power at the compressor ( clutch). If the pressure in the system, gets to low, the low pressure switch will open, and you have no power at the AC compressor (clutch). When the system is at high fan speed, there is more air flow, across the evaporator core. At low fan speeds, less air flow across the evaporator core. So the freon can freeze up, easier. This is why, it is critical that you have the rite pressure. If you don't have a set of AC gauges, I know harbor freight sales them, for less than $100 I think. Watch some videos on YouTube, on vehicle AC freon recharging.

 

[Tonys87]

Yeah, it is imperative that the pressure is correct, for the AC to work rite. I have tried, and tried, and tried to do that work, without putting gauges on the system, and that just doesn't work. You must see all the pressure to get it rite

I have gauges. That is used while vacuuming down the system and while adding the r134a. I just don’t have any number to compare.

 

[tayto]

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[kennythewelder]

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Yeah, I have used the same chart, but that is for with the system, running. When the system is not running, with you engine off, the freon equalizes in the system. Here is a chart, that gives you those pressures. If you get all of these pressures within spec, your AC system should be properly charged. If you are still having issues, then you may have orifice tube issue, or other problems

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[Jimbo2312]

Hey Tonys87, happy you changed everything out versus just the compressor. I redid my AC system like you did last August, had similar short cycling with the compressor. I am not an expert on it, so I called the experts and they told me how much refrigerant my truck needed, I’ll try and see if I can get the phone number. But I used a scale to measure out the last can. Also, when I crossed into the Rockies and gained a few thousand feet, it was over-pressurized and I had to bleed some out.

 

[tayto]

Hey Tonys87, happy you changed everything out versus just the compressor. I redid my AC system like you did last August, had similar short cycling with the compressor. I am not an expert on it, so I called the experts and they told me how much refrigerant my truck needed, I’ll try and see if I can get the phone number. But I used a scale to measure out the last can. Also, when I crossed into the Rockies and gained a few thousand feet, it was over-pressurized and I had to bleed some out.

don't need to call the experts. there's a sticker under the hood that is required and tells you exactly how much to fully charge your system.