Medium and Heavy Trucks
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Hi, my name is ***** ***** you for your question, I will try and help you out.
Take a pair of needle nose vise grips and crimp off one of the heater hoses just in case one is leaking by internally when engine gets hot after running half day.
If you have a set of gages we can diagnose other issue so you don't need to bypass.
When you say you replaced all ac parts please list parts changed?
I think you are saying ac clutch cycles to much without system bypassed ,how much freon do you have in system?
Sleeper ac or no?
Let me know either way please
Thanks for the info, let me see if I can find a wiring diagram, I think this system uses one more sensor that can kick clutch in/out but I want to be sure. I need my coffee first too!!
I can't find any diagrams for this are you having any engine low power or overheating issues,, maybe the engine ecm might be turning it off to try and cool engine.
Any engine codes?
Just got out of shower let me take a look and see If I can blow it up.
Okay this is showing 3, ac pressure switches, I blew up a copy for you,,,check the cab through wall (pass thru) connector on firewall,
it's possible you are losing a good contact when you rev engine (possible broken mounts allowing wires to be pulled)
I attached the picture of plug I want you to check but I'm not sure it's attached but I will check after I reply,,if it does not go through I will do over.
Lets try again
Did you ever check amp draw on ac clutch?
If ac clutch uses a breaker and most Pete's do it may be tripping breaker and not be a ac issue.
Let me know
After thinking about this some more I think you got a defective low pressure switch ,I have seen this happen before with new parts,,a customer or service tech returns part so they don't have to pay or warranty won't pay and the part was actually bad.
Bypassing ac low pressure switch the system works fine so that confirms everything else in the system including wiring and all is good, so you either have low pressure there or the switch is defective.
If you want to test to confirm back probe the sensor wires with meter reading on ohms and see if its dropping out when ac clutch does.
Yes there can be a issue with schrader valve, if its not fully unseating when switch is installed,that would explain a sudden drop in pressure and when clutch kicks off allows time for freon to refill and turn switch back on.
If you have a laser temp gun I would check the temp of low side of system including evaporator and look for a hot spot,that would indicate a partial blockage,
I would do that first then evac system ,change schrader valve,remove and check new orifice tube for any contamination or excessive oil trapped in screen,,that may be partially blocking flow.
Okay sounds good let me know if you need me to look at it
When you changed pressure switch did you also replace schrader valve?
I know what you mean about not having truck.Always worth a shot to avoid downing truck!
One place I worked for the drivers where supposed to swap out their inventory (jays potato chips) for when I needed their truck to service or repair it,,,,it was like pulling teeth!
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