This is a surprise, because I have not seen them work on my 1995 E300D.

Last summer and this, my AC has only blown cold when the car is moving (or was recently moving). Sitting in rush hour traffic gets warm. In fact, I keep an eye on the temp gauge, and turn off the AC when the temp gets over 110ish. On a day like today, with outside temps over 100, and not a puff of wind it is less than fun.

Today, I was close to home, and the engine temp was getting up. I made a brief stop to give a neighbor some mail that had dropped near the mailbox. When I got into the car, I heard a new noise kick in. I drove home and popped the hood to confirm that both auxiliary fans were turning.

Now I know the fans work. This is good! However, I want those fans to come on before the temp gets over 115. Is this conclusive evidence that the pressure switch is bad, or an inconclusive indication that the switch is bad, or refrigerant pressure may be low?

I lean towards bad switch, because I have had the refrigerant pressure tested before, and I was told it was fine.

Also, what can I do to get the fans to come on high at an engine temperature closer to 100 than 120?

Thanks!
Tom

__________________
2016 E350 4matic wagon
2010 ML350 Bluetec
1995 E300D Gone, but not forgotten.

Those fans work in 2 stages, the A/C function is low speed and the engine too hot function is high speed.

The low speed A/C function works from the switch on the dryer itself and the circuit is wired through the resistor, the wiring can burn out at the resistor which can cause the low speed not to work, however the high speed function may work because the wiring to it bypasses the resistor.

In any case the mechanical cooling fan has enough oomph to cool down the engine and A/C condenser at above idle speed, the aux fans at low speed move a scant amount of air just enough to slightly cool the condenser and engage the fan clutch with the exhausting hot air.

My car is similar to yours and also live in Texas and my temperature almost never crosses 95 with A/C working sitting in traffic. Test the fan clutch when the temperature gets above 100, if the fan does not roar or blow a gust of wind on revving then the clutch is bad. And your engine will overheat.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Thanks! I sure appreciate your insights.

I tested the fan clutch earlier this summer as vstech suggested in an older thread. It seemed OK according to his method.

I see where the switch is at the AC compressor for low auxiliary fan operation. Where on the head is the switch for high auxiliary fan operation? Regardless of what I find with regards to the fan clutch or refrigerant pressure switch, I am concerned that this temperature switch does not trigger the electric fans until temp is approaching 120.

Thanks!
Tom

__________________
2016 E350 4matic wagon
2010 ML350 Bluetec
1995 E300D Gone, but not forgotten.

The high speed fan operation is controlled by the HVAC unit on the dashboard, the sensor for it is the two pin one near the top radiator hose, You can add a resistor on it, (look for the cool harness trick) to make the fans trigger earlier - near 105 or something.

To check the operation, remove the two pin connector, if the fans switch on the circuit is working, test low speed by bridging the two brown wires on the refrigerant switch. If you dont see any action, check the fuse and the resistor for burnt wiring.

As I have the same car Im telling you from experience that if the mechanical fan is weak or the radiator/condenser is blocked with dirt/bugs the engine will show elevated temperature. Dirt/bugs will also cause the mechanical fan not to engage as air is not moving and the fan BMS requires hot air to make it bend to make the clutch work. I had a dead fan clutch which I refilled with lucas 3000 cst fluid, cleaned out the condenser fins and also did a citric acid flush. The engine temperature has not gone above 100 yet, even in 100 deg weather with A/C working really cold.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Awesome!

Thanks!
Tom

__________________
2016 E350 4matic wagon
2010 ML350 Bluetec
1995 E300D Gone, but not forgotten.