AC issue with supplemental fan
 

At what point does the supplemental fan go on on a 124? It was 95 out and the fan was not going on eventhough the compressor was trying to push freon around. I don't think it goes on when AC is activated, but at 95 ambient, I would think it should be helping with the cooling.
Is there a test of relays or temp. sensor when this should activate.

Thanks.

The aux fan kicks on under two conditions:

Low Speed:
When the a/c high side pressure exceeds a certain value (not sure of exact value)

High Speed:
When engine reaches a certain temp (not sure of exact value)

So if neither condition is met, no fan.

Many people modify the wiring so that the low speed fan comes on when you kick on the a/c or just wire it up so it run all the time.

Another mod is to wire in a resistor on the sensor so that the high speed mode activates sooner than the normal set point

The aux fan kicks on under two conditions:

Low Speed:
When the a/c high side pressure exceeds a certain value (not sure of exact value)

High Speed:
When engine reaches a certain temp (not sure of exact value)

So if neither condition is met, no fan.

Many people modify the wiring so that the low speed fan comes on when you kick on the a/c or just wire it up so it run all the time.

Another mod is to wire in a resistor on the sensor so that the high speed mode activates sooner than the normal set point

My fans kick in at engine temperature of 105 centigrade. It's triggered by a 2-pole sensor near the water pump. Mine's doing it all the time in traffic as the fan clutch has gone lazy. Happily, temperature quickly drops to around 90 before the cycle starts again.

You can measure the sensor at various temperatures with a multimeter. Easy and cheap to replace if faulty.

Bonne chance.

RayH

Is this as simple as jumpering the red pressure switch? I believe mine is faulty and want the fans to run on low anytime the ac is on.

I don't believe so. That would cause the fans to be on all the time. I think..


IMO, the best way have the fans on all the time would be to use a relay and come off the compressor clutch.

Wire the relay so that the coil is energized when the clutch comes on and then have that supply power to the fans.

Hmm, maybe OK with all the time. The next time the ac won't run is probably December...