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2nd Gen Ram Tech1994-2001 Rams: This section is for TECHNICAL discussions only, that involve the 1994 through 2001 Rams. For any non-tech discussions, please direct your attention to the "General discussion/NON-tech" sub sections.
Back in the spring of 2022 during a heater core replacement I replaced the evaporator, receiver/dryer and compressor. I also had the condenser flushed and filter replaced. Things have been working great until this year when the compressor started short cycling. Cooling is mediocre and intermittent. Figuring it was low of refrigerant I connected one of those gauges that comes with a refill kit and it read in the red area. Not sure if it was reading correctly I added 10.8 oz of refrigerant. It may have helped a little, but issue remains. I connected a set of gauges to the system and made a couple of videos to show what it is doing. I have attached them here and also provided an iCloud link. https://www.icloud.com/photos/#/iclo...r42nvde7yk8ChA
I do have a problem with the temp blender door when sometime it does not fully open/close with the ****. I sorta have to get lucky to put it in the desired spot with the fan off. I figure it is binding or the control is not working properly. When I replaced the heater core there was good movement in the doors. Not sure if this has anything to do with it or not but figured I would mention it.
Between 180 and 250 PSI.
For the Hot / Cold air selector I have an early model that does not have that actuator. Found that out after I bought the Heater Treater kit.
Replace your low pressure switch (clutch cycling switch)
You can mail me your heater treater. Today I removed my evap to clean all the clogged fins and sure enough the plastic coupler the heater treater fixes is broken. Epoxied the plastic coupler tonight (see pic)... should not break again, now the blend door moves freely. Hopefully.
Pulled my airbox today.
Good news, I've had the 2nd gen for 19 years and she's never leaked her full refrigerant charge. I did only recover 14oz of the required 32 ounces of r134a. OK by me if it takes 19 years for 18 ounces to leak out.
Bad news, had to use my $90 empty recovery tank to recover that pitiful amount of r134a. Had planned on using that tank for a different refrigerant. Might burp out non-condensables and reuse the r134a so I can vacuum out the tank and use for its intended refrigerant. Can't do an accurate saturation pressure test for non-condensables because there has to more more refrigerant in there as I need at least a little bit of liquid r134a in there (it's just vapor in there). Maybe I'll just transfer that to 12oz cans with the self-sealing tap and put it in the shop somewhere *whistles innocently*
Also found the reason why the plastic blend door coupler cracks. That metal pivot at the top of the blend door corrodes and seizes up. Door needs a lot of force to move back and forth. Stresses the plastic coupler to the breaking point. Was impossible to turn the blend door working the bottom of the pivot by hand and even pressing the blend door back and forth was met with a lot of resistance. Removed the blend door and sanded the top pivot and lubed it today so the blend door turns more freely. The vacuum actuator holds the blend door steady, zero reason for that top pivot to have any resistance. Even a heater treater isn't fixing the problem of that top pivot being seized up. In fact it might wind up tearing up the actuator gears or eventually burning up the motor.
EDIT: rewrote this diag. At first glance I thought maybe your gauges were designed weird and you're running at 15psig. Was thinking "no way that's running at 65psi" Looked again and yeah, you're running suction side of 65psig. Removed my original writeup.
Looks overfilled. Hopefully your newish compressor isn't failing. Need correct amount of r134a to properly diag. Go to walmart, firestone tire center, or other tire center or shop that doesn't do full service repair. They should have a special on "AC Recharge Service" for about $70. They will recover your r134a, vacuum, and charge with the correct amount of 2lb of r134a. Either overcharged or compressor going bad and can't get suction side any lower. With suction side at 65psi, evap temp is 66F. For suction side normal operating pressure the PSI reading is roughly equivalent to the evap temp (in F). Kinda nice how that works out.
You might incorrectly thought you're low on refrigerant charge. Might be clogged orifice or out of spec low pressure switch (aka clutch cycling switch) which caused you to add more refrigerant. You can't "top off" or "add a can" like you can when filling up the gas tank. Need a specific weight of refrigerant in the system for correct operation and long service life of the system.
An out of spec clutch cycling switch might let the suction pressure get too low. While the evap can operate at 25psig (with good airflow) getting lower than that can ice up the evap and the ice will block airflow, reducing or stopping cooling altogether. Right now your clutch cycling switch is closed because your suction pressure isn't getting anywhere near the 25psi cutoff. You might have misdiagnosed an iced up evap as "low on refrigerant" and now it's overfilled.
good news: clutch cycling switch, if it's out of spec, can be replaced without needing to recover the r134a in your system
bad news: if your orifice is clogged... you do need to recover the r134a, replace the high side line containing the non-replaceable orifice, vacuum, and recharge by weight the correct amount of 32oz.
make two videos of the manifold gauges.
1) doors open, Max A/C, fan on HIGH (high heat load)
2) doors closed, windows up, Max A/C, fan on LOW after you get the cabin cool. (low heat load)
That'll help me help you. Kind of doubt we'll be able to do further diag if you are overfilled. You're gonna be running too high of a discharge pressure since your condenser is flooded.
video on adding correct amount of refrigerant by weight on empty system using a cheap digital postal scale:
troubleshooting short cycling (out of spec clutch cycling pressure range (failing clutch cycling switch) and low airflow from clogged cabin air filter (my GM truck which HAS a cabin air filter):
Another AC Problem
Today I removed my evap to clean all the clogged fins and sure enough the plastic coupler the heater treater fixes is broken. Epoxied the plastic coupler tonight (see pic)... should not break again, now the blend door moves freely. Hopefully.
