Fans work via otter but not with AC switch

[Flash66]

Hey Gang,

Noticed my AC was blowing warm yesterday and all of a sudden cooling fans came on with temp up. So the fans are not engaging with the AC switch, but work fine via the otterstat. My AC clutch engages fine. I've got 2 fused jumpers that tested good replacing the fan fail etc. it has always worked fine until yesterday. Anyone ever have this issue before?

[DMCMW Dave]

Check the diode in the circiut


Sent from phone

[David T]

Check the diode in the circiut


Sent from phone


Verify the clutch is actually engaging. If the refrigerant is low and the low pressure switch is not allowing the compressor to engage it also won't run the fans. If the clutch IS engaging and the fans are not running then it could be the diode. You say the A/C is blowing warm, make sure the compressor is running.

[Flash66]

The clutch is running. When the fans came on via the otter the AC blew cold. What made me realize there was something wrong, was the loud pop of the pressure valve opening briefly from the fans not running air thru the condenser and building up a lot of pressure. Just to clarify, the valve opened up for a split second. I didn't lose much gas.

Where is the diode located? Is it #20 in this diagram?

http://tapatalk.imageshack.com/v2/14/10/23/cc4d85c64decc0330589a4e1b310e15c.jpg

[Bitsyncmaster]

Diodes are hidden in the wires in harness. Look at the harness right side near front in the relay compartment. Just try to unplug and plug them back in and it will probably work again. But if you heard a pop, you may not have any freon in the system.

[David T]

Diodes are hidden in the wires in harness. Look at the harness right side near front in the relay compartment. Just try to unplug and plug them back in and it will probably work again. But if you heard a pop, you may not have any freon in the system.

Once you get the fans going you need to check if you have enough refrigerant and if the relief valve is leaking. Sometimes after they pop they do not seal tight anymore and must be replaced. If you are sure the clutch was engaged and the fans were not working it could be the diode or possibly the circuit breaker for the fans. The fans could be cycling on the breaker and you think it is the otterstat switch.

[DMCMW Dave]

31263

Right about here.

These are marked as "189" on the schematic. One is in line with the compressor and one with the otterstat. The purpose is so that when the otterstat turns the fans on due to engine temp, it doesn't backfeed and turn on the compressor. If the one in line with the compressor fails the fans will turn on with the otterstat but not the compressor (actually turned on by the low pressure switch).

[Flash66]

Thanks to all three Dave's! I found them and yes, the cathode side of the diode connector was broken. Peeled the plastic back a bit and soldered a new connector to it. AC is super cold. I'll throw some gauges on it to check the pressures but I think I got lucky with the relief valve! It was a quick burst that only lasted a second.

[SS Spoiler]

I love it when "The Daves" jump in. It's almost like our own private Google / artificial intelligence.

[DMC-81]

I love it when "The Daves" jump in. It's almost like our own private Google / artificial intelligence.

+1

These are educational threads. Thanks all for taking the time to offer your advice as it benefits everyone who reads them. I also enjoy reading the successes. I bookmark several of these threads if it will help me on a known restoration area on my car.

Bravo!