AC clutch cycling on low fan setting.

[Tonys87]

Thanks for the update. Just a FYI, I have used the freon with stop leak, before, for very small leaks, and it has worked for me, for a while. A lot of people hate that stuff, and have bad things to say about it. If the leak is real small, and you can not find it, sometimes the Schrader valves can be the culprit. That's what me issue is. It took me a long time to figure that out. The chances that the evaporator core it self has a very small leaks, are slim. I have been in your situation many times. You look for the leak, and you just can NOT find it.. keep the system going, and give it some time, then, pull the blower fan, and look inside the HVAC box with you UV light. If there is a leak in the evaporator core, the UV die will be inside the HVAC box after enough for leaks into the box.

Just answered a question I had about how to confirm the evaporator is leaking. Thanks!

 

[Tonys87]

Not the best picture but this is what I see after removing the blower. Leak for sure??

 

[kennythewelder]

Not the best picture but this is what I see after removing the blower. Leak for sure??

Man, that sucks, but at least you know for sure, where the issue is.

 

[Tonys87]

Man, that sucks, but at least you know for sure, where the issue is.

Do you know of any good write ups or videos, since it’s not my daily, I am going to try and do it myself.

 

[kennythewelder]

There are some videos on YouTube, but what one is better than the other, IDK. If you have a set of gauges, there are 3 things to look for. #1,High pressure at rest, so engine off, and looking at a chart for that.
#2 high pressure, with the engine running, and then
#3, low pressure, with the engine running.
All of this has to go along with the outside air temp. Humidity is a factor, but outside air temp, is what is more important. Also 134A is slow to react. Get things close, take it for a drive, then check it again, when you return. Look at some videos also, that explain how the office tube works. That's what makes the pressure different, from low to high.

 

[letitsnow]

How often should the compressor cycle on/off on these trucks?

 

[kennythewelder]

How often should the compressor cycle on/off on these trucks?

It's all related to the pressure switches. There is no set, time that it turns on, and turns off. That being said, if the compressor kicks on for a few seconds, then kicks off for a little, and keeps repeating this, that's a sign, the the system is low on freon.

 

[L31MaxExpress]

How often should the compressor cycle on/off on these trucks?

They can cycle pretty often if the cooling demands are low. If I am only using the front blower and it is on one of the two lower fan speeds my van cycles every 15-20 seconds to prevent the evaporator core from icing up. My Tahoe was the same way. At highway speeds even on a hot day with both blower fans on high speed the compressor will cycle every 30 seconds or so with the discharge temps in the low-mid 30s at the vents. I have a 25% under driven crank pulley as well, stock pulley cycles more often.

 

[L31MaxExpress]

Not the best picture but this is what I see after removing the blower. Leak for sure??

Looks like it is leaking to me. Evaporator core leaks are not uncommon. My 97 van started leaking in 2011 with less than 70K on it. It had a ton of garbage in the case that was holding moisture against the core and rotted the aluminum out. Luckily the van core is under the hood, quick and easy to gain access to. You can see where the pag oil was leaking on the lower left of the core in the picture and the oily buildup on the case bottom. AC dye was dripping out of the box on to the frame.

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