Discussion in '6.9L IH & 7.3L IDI Diesels' started by rewbrooks50, Jul 13, 2019 at 4:52 PM.
What is causing the ac clutch to cut off? I tried a jumper in the high and low switches, with no change.
Pictures above post. Top is reading when the clutch is engaged. The second is after the clutch disengaged.
Seems like the high side pressure is too high even for our texas heat, and low side is a bit low. The orfice tube may be clogged causing a buildup of pressure on the high side and not enough flow to the low side. Is the clutch cycling rapidly or not at all?
If it's around 100 degrees outside, the high pressure side will read up to 250 psi won't it? You may have to rev the engine a little bit to get a reading that high. I think he is still a little low on refrigerant.
And if this is a conversion, you might have to tweak the pressure switch setting. If you unplug the wiring plug to the low pressure switch located on the dryer, look in between the electrical connections on the switch and you will see a small screw. You can turn that a little bit, plug it back in, and see if it runs a little longer or a little shorter. If it runs a little longer you are going the right way. A little shorter and you need to turn the screw the other way.
Low on freon as franklin2 says. Low side too low, high side too low also. Low should be between 32-40psi & high around 250psi. Buy a cheap digital thermometer and keep in center vents to keep an eye on cooling. About $8
you are low on freon. if its a 134a system heres a psi chart
While he is of course low on freon, he said he jumped the high and low switches. In these systems, that should eliminate anything but a clutch failure/ incorrect air gap.
I imagine however that he likely only jumped one switch at a time, allowing the other to cause cut-out.
Always start by checking refrigerant levels anyway, they are by far the most common cause of issues.
Yep y’all are right, both are low looking at the spec now, could be a slipping clutch or an air gap issue. You can take the clutch apart and get the gap tighter.
Maybe it's not very likely, but maybe you have a bad connection at the plug on the compressor. Maybe it shakes around and loses contact and then, after a while, it makes contact again.
Excellent point, should've mentioned this as well. My high pressure switch on a 95 psd I've got would do this exact thing. I could watch the compressor "cycle" out of sync with gauge pressure and cab temps and sometimes it was short cycling and other times long cycling. Bumped the high side switch moving clutch wires around and found I could control the clutch on command with the high side switch by wiggling the connection.
Great call here
It was a suggestion, but it is free and easy to check.
The clutch is cycling at first and blows cool air. Then stops working. I added a can of 134 with dye and it still cut off. And my gauges were still not showing the right pressures. I have pulled, jumper wired and reconnected the high & low switches. I need to get UV light to check for leaks. I'll try that tomorrow.
Should I evacuate the system and the replace orfice tube and recharge. What else should I replace? Or, do a new compressor kit? How hard is it to pull the evaporator to clean?
Thanks for the replies so far. I will try each suggestion.
I will try this next. My Dad always told me and my brothers, try the simple repairs first.
Air gap or tired coil
I will reset the gap this weekend.
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