Hot under the hood in Fla.
 

Hi All:

I have a 1996 300 Diesel that is having some over heating problems and AC problems that seem to be intertwined.

The car runs great on the highway with the water temp staying in a normal range. On the highway the AC also works great. The AC also works well when the car is cool at an idle.

After the car warms up, in city traffic the temp water temp will get almost up to 120 and the AC will not work and blow hot air.

Any ideas are greatly appreciated.

Thanks.

Matt

we are going through this on the 300e.

We are replacing the fan clutch... also doing some other work while we have the radiator out.... new belt, thermostat... coolant flush...

thought i might have to do the fan bracket pulley... but it's fine

Matt,

I think you aux fans are not working. They are suposed to run on low speed when the A/C is on and in high speed when coolant temp reaches 105. Check those first. There are some fuses related.

Hope this helps.

And here's how to check them.

With the key in position 2, press and hold both AUTO buttons for >10 seconds (it takes about 12 seconds for my car). The fan should start at full speed.

If not, press the REST button for >5 seconds, until the display changes to 1 on the left side. Press the left AUTO button until the left side reads 20, and the right side should read 10. That means that full power is demanded from the auxiliary fan. If so, report back.

If there is a fuse for that fan, I don't know about it.

Thanks all:

I'll give them a shot and let you know.

Matt

I don't know in that car but in mine, there is a relay compartment behind the fuse box, close to the firewall on driver's side. Inside that box there are two relays (high and low aux fans). I think one is green and the other one is blue. Each relay has a fuse.

I hope this helps.