I recently replaced my radiator, and my car is running much cooler than before. However, it runs noticably warmer with the air conditioning on. The temperature gauge reached 105 the other day with the A/C running (outside temp was 73). While this is not too far away from normal, it seems relatively high considering the new cooling system equipment.

I called a tech at Mercedes-Benz, and he told me that one of my auxilary fans should be running whenever the A/C is in use. I have only seen my fans run once, and that was before the radiator was replaced.

What could cause my fans to not switch on? I did a search on this site, but I only found a limited amount of helpful advice. Maybe my searching skills are not up to par.

I need to fix this problem, as I am quite nervous about overheating my engine. Any help will be greatly appreciated, and will help me sleep better.

Is 300D or 280 SEL ?

I'm sorry, I should have included that. It is the 300D.