I would expect a plugged orifice to cause abnormally High side pressure. Unless the system is just very low on refrigerant.
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Location: Reedsburg, WI
Posts: 4,026
My VIN: 5180
Club(s): (DMWC) (DCUK)
I would expect a plugged orifice to cause abnormally High side pressure. Unless the system is just very low on refrigerant.
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DENNIS
VIN 5180, Frame 3652, STAGE II, DM-eng Solid State Solutions (RPM Rly, Dm.Lt.Mod., Fan Fail Mod. , FAN Rly, HS.Rly) , HID headlights, SPAX user since 2009, Eibach springs, M Adj. Rear LCA's, DPNW poly-sway bar kit, DMCEU LCA Stabilizer link kit, DMCMW Illuminated door sills, Aussie Illuminated SS Shifter plate, REAL MOMO EVO Steering wheel, DELOREANA Extended View Side Mirrors w/ Heaters, DELOREANA LED Door Lights.
Location: Northern NJ
Posts: 8,583
My VIN: 10757 1st place Concourse 1998
One way to check what is going on is to remove and measure the amount of refrigerant. For the pressures to look correct and no cooling several things would have to be bad at the same time. Verify you are moving enough air over both coils. It is possible to have the correct high side pressure with low refrigerant if the condenser coil is not dissipating heat because of insufficient airflow due to bad fans or dirt blocking airflow. On the low side the evap coil could be freezing over.
David Teitelbaum
Posts: 448
One scenario that would explain the AC working but no cooling is the heating is stuck on and working simultaneously. Combination of evaporator cooling plus heating coil heat gives you warm air. You should be able to eliminate the heat by putting the mode switch to MAX. But that assumes your heat valve works. Observe and verify that the heating valve is closing when MAX is selected. Even if it looks like it's working, you could clamp the heater hose near the valve to close it off for testing.
Heater Valve sketch.JPG
If you find the heating coil is the culprit, you'll need to look into the heat flap to see why the cooling from your evaporator is going thru the heating coil. Normally this is regulated by your temperature control knob.
Ron
Dave M vin 03572
http://dm-eng.weebly.com/
At present, I'm still leaning more towards some type of physical blockage in the airbox. First, I would believe it would be highly unusual for the compressor pressures, cycling, etc. to be perfectly in spec if there were problems in that part of the system. Second, my wife said she thought there might be a mouse nest in the box as she saw little puffs of lint keep flying out of the round air portals on the sides of the dash for the door air vents.
Some things I'm thinking I should try:
- test the a/c with the car cold. Then there's no interference from the heater core
- feel the accumulator/drier to see if it's getting cold.
- drop the blower fan and look for signs of blockage
- drop the bottom of the evaporator's housing
- check the hot water valve, just because it was the last thing replaced.
Thanks to all for the continued suggestions and help!
Sounds like a diverter/duct problem to me too (if accumulator cold).
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fwiw, a partially restricted orifice would make the high side go high and the low side go low. Blocked, the high side would go extremely high and the low side go negative (vacuum). Bypass LP Switch to test.
If those pressure readings were taken when the clutch cycled out, they are near perfect for that ambient temp.
Ok, finally got a chance to look at a few things. I dropped the fan so I could feel around for any obstructions/mouse nests, but it was all very clean. The accumulator and evaporator both get cool -- but not cold -- when the a/c is on.
Some other things to note:
- tested from a cold start so there was no interference from the heater.
- the compressor's 'on' cycle is only 2-3 seconds, with around 60 seconds off
- the cooling fans don't come on when I turn the a/c to max. Aren't they supposed to stay on? I am running a Fanzilla so there is a delay before they kick on. I jumpered the fan at the otterstat and they ran fine.
Not sure what to check out next. Ron's suggestion of checking the pressure switches makes sense... Any thoughts? Thanks again, all, for the assistance!
Last edited by Project Vixen; 08-22-2018 at 08:49 PM.
Location: Mebane, NC
Posts: 346
My VIN: 06668 81' Grey interior, 5 speed, Grooved hood. Previous owner of 16301, in 2001. Found Nov 2019, a
I believe the Fans should kick on on max. Set the switch to Max, and turn the ignition switch to run, without starting the car and see if the fans kick on. Also check and make sure the recirc door is opening on max and the Hot water valve is closed. I recently learned that they only operate on the Max setting.
Location: Reedsburg, WI
Posts: 4,026
My VIN: 5180
Club(s): (DMWC) (DCUK)
DENNIS
VIN 5180, Frame 3652, STAGE II, DM-eng Solid State Solutions (RPM Rly, Dm.Lt.Mod., Fan Fail Mod. , FAN Rly, HS.Rly) , HID headlights, SPAX user since 2009, Eibach springs, M Adj. Rear LCA's, DPNW poly-sway bar kit, DMCEU LCA Stabilizer link kit, DMCMW Illuminated door sills, Aussie Illuminated SS Shifter plate, REAL MOMO EVO Steering wheel, DELOREANA Extended View Side Mirrors w/ Heaters, DELOREANA LED Door Lights.
Hmm. I agree that a 2-3 second on cycle time and minimal cooling typically points to a low refrigerant condition. With a full charge of R-12, my compressor seems to stay on all the time in these summer temperatures. Ignoring any impact of the Fanzilla unit, yes, as mentioned, as soon as you click the Max mode on, the fans come on immediately and stay on.
I agree to check the pressure switches. I originally had similar problems with minimal cooling and after lots of troubleshooting my problem turned out to be an oil logged evaporator. Apparently this problem has degrees of severity, and mine was completely blocked so I had no pressure building.
Off topic, I just want to thank you for the great information on rebuilding the door lock solenoids. I was able to do the same thanks to your information.
Dana
1981 DeLorean DMC-12 (5 Speed, Gas Flap, Black Interior, Windshield Antenna, Dark Gray)
Restored as "mostly correct, but with flaws corrected". Pictures and comments of my restoration are in the albums section on my profile.
1985 Chevrolet Corvette, Z51, 4+3 manual
2006 Dodge Magnum R/T (D/D)
2010 Camaro SS (Transformers Edition)