No fans, No AC

[Oliver Holler]

Hi Folks,
I heard some fast rhythm clacky-chattering from my relay bay a few weeks ago while driving. Just occasionally.
It would stop when I turned off the A/C.
Occurrences increased until A/C quit blowing cold air.
Also, front radiator fans quit working at the same time! Oh, no!
So, I pulled into NAPA and replaced the relay. No difference.
I replaced the circuit breaker. No difference.
I jumpered the otterstat wires and BEHOLD! I had fans AND cool air once again.
Fans stayed on, which was expected and it got us home, however, the A/C would not cycle as the clutch on the A/C compressor never turned off.
So, we didn't use the A/C, to prevent something from 'sploding.
Ordered an otterstat, installed it, (removing the jumper wire, and enjoying a nice bath of coolant!) Now I'm back to no fans, no A/C again.
I'm not real good with using meters, but does anyone have an idea of what thing (things) might be happening?
I've replaced everything I can think of. :(
Thanks,
Oliver

[DMC5180]

The A/C compressor should NOT run when the Otterstat is Jumpered. It is DIODE protected. So it could mean your DIODE is know longer doing it's job. The DIODE is in the MAIN harness bundle just to the right of the fuse box. It will have a Pink wire on one end with Doubled Black/orange on the other. Disconnect it and see if it is flowing continuity in both directions.

[Ron]

I was just thinking about this...sounds like it was re-wired just to make it work...then failed

Dennis, I'm with you on the diode being shorted closed, causing the compressor to run when the Otterstat calls for the fans, but that would also mean that he couldn't turn the compressor off by turning off the AC, but he says he did....coincidence/perfect timing, maybe, but it wouldn't stay off.

EDIT: Also, if your AC was OK ie the clutch was cycling, none of the above would make it stay engaged...it would have a bad low pressure switch at the very least...

If you can read a schematic (http://dmctalk.org/showthread.php?17-DMC-12-color-wiring-diagram) at all, I suggest checking for changes to the wiring first.

[DMC5180]

Hi Folks,
I jumpered the otterstat wires and BEHOLD! I had fans AND cool air once again.
Fans stayed on, which was expected and it got us home, however, the A/C would not cycle as the clutch on the A/C compressor never turned off.
So, we didn't use the A/C, to prevent something from 'sploding.
Ordered an otterstat, installed it, (removing the jumper wire, and enjoying a nice bath of coolant!) Now I'm back to no fans, no A/C again.
I'm not real good with using meters, but does anyone have an idea of what thing (things) might be happening?
I've replaced everything I can think of. :(
Thanks,
Oliver

Oliver,

Did you ever let the engine fully warm up with the NEW otterstat to trigger the fans ON. You kinda jumped past the tested the new Otterstat part. Fans should at least run with the Otterstat switched ON (same as Jumping the 2 wires right).

A/C clutch would tend to run continuos at Idle if the system is fully charged and the Fan is on 3 or 4 under the right conditions. Usually raising the RPM to 1000 or better will get it to start cycling Off. Generally a low freon condition will cause the system cycle rapidly. (unless the Low-pressure switch has failed/stuck closed) then it would not shut-off.

What happens when you turn the key to the RUN position, then switch the mode switch to A/C MAX? Normally you can Here the A/C Clutch-POP-in and the Fans Start running. Are you saying this does not happen?

[Oliver Holler]

Thank you for the suggestions.
Correct, Dennis. I was so worried about the engine overheating, I didn't test the new otterstat!
Drove it around close to home in the July heat and...
Good news: It works and both front fans work and come on at a good temperature!
Bad news: The a/c compressor clutch won't engage no matter what setting the selector is on.
So... I figured I'd buy a can of refrigerant, assuming it was low.
But when I snapped the gauge on the low pressure side, it was OFF THE CHARTS!
WAY too much pressure!
Not sure how this could happen, unless it built up if the clutch stuck on and I didn't notice.
So, I bled it down to a reasonable pressure level. Some of the refrigerant spit out in a frothy light brown foam.
Still, no action.
:/

[Jonathan]

So... I figured I'd buy a can of refrigerant, assuming it was low.
But when I snapped the gauge on the low pressure side, it was OFF THE CHARTS!
WAY too much pressure!
Not sure how this could happen, unless it built up if the clutch stuck on and I didn't notice.
So, I bled it down to a reasonable pressure level. Some of the refrigerant spit out in a frothy light brown foam.
Still, no action.
:/

If this was my car, this would be my signal to take it to a shop and have someone who works on air conditioning systems for a living have a look at it. Just me anyway, your DIY abilities might be different than mine.

[DMC5180]

Just sticking the gauge on without having the compressor running will show high. When the system is static, all internal pressure is equalized. Try jumping the low pressure switch connector too see if that makes the clutch and fans run. The switch is on the A/C accumulator behind the right front wheel.

[DMCMW Dave]

Just sticking the gauge on without having the compressor running will show high. When the system is static, all internal pressure is equalized. Try jumping the low pressure switch connector too see if that makes the clutch and fans run. The switch is on the A/C accumulator behind the right front wheel.

Yes - in high temperature the pressure in the system is probably the same (in fact it has to be) as the pressure in the can. Probably 75PSI or higher. My guess is that your system is (or was) charged just fine and you are chasing an electrical problem. And (now) have a system that is low on charge.

[Bitsyncmaster]

Just look at the static pressure chart for R-12. That chart shows you the pressure at the ambient temp (air temp if your engine has cooled). You will get that pressure with 1 oz of liquid freon or the correct 2 lbs of liquid freon. If your pressure is below that value you have no liquid freon in the system (empty).

[Oliver Holler]

And that's what makes owning a DeLorean so great. Fellow owners!
Dennis- I used a paperclip to connect the terminals of the low pressure switch, and sure enough, the compressor kicked in!
Replaced the switch, and all is good now. I added the can of R-134 since I had bled some out of the system and was low (correct guess Dave!)
I still think the 150+ off the chart pressure gauge reading seemed excessive.
I panic, especially when out on the road, and start shooting at anything that moves.
I'm grateful for the level-headed folks here who offer a broad range of knowledge.
THANK YOU.
Oliver
10694
ToTheFuture.org

[DMC5180]

Glad things worked out. :thumbup: