1987 300E Aux Fan Operation

[murphysf]

Hello

I am trying to understand the operation of the AUX fan that is mounted on the front of the radiator. I have searched previous posts and also on google, lots of information but some details are still missing.

To make things simple, let me ask two questions:

If the AC is off what conditions need to happen for the AUX fan to come on?

If AC is on what conditions need to happen for the AUX fan to come on?

Thanks

[Arthur Dalton]

[QUOTE=murphysf;1500563]Hello

I am trying to understand the operation of the AUX fan that is mounted on the front of the radiator. I have searched previous posts and also on google, lots of information but some details are still missing.

To make things simple, let me ask two questions:

If the AC is off what conditions need to happen for the AUX fan to come on?

The coolant temp has to reach 105C..this is fan high speed.

If AC is on what conditions need to happen for the AUX fan to come on?

The a/c high side pressure switch detects a high thermal load and triggers the fan relay. This is low fan..

[murphysf]

Hi

The fan switch has a rating of 105/115C. What does this mean?

I've read three different things:

105 fan on low, 115 fan on high

105 fan on, 115 cuts off ac compressor

115 fan on, 105 fan off

Help!?

[Arthur Dalton]

[QUOTE=murphysf;1500706]Hi

The fan switch has a rating of 105/115C. What does this mean?

I've read three different things:

105 fan on low, 115 fan on high
Incorrect

105 fan on, 115 cuts off ac compressor
Correct

115 fan on, 105 fan off
Incorrect