Gordon Cooke

Hello all,
I replaced the auxiliary pump on my 2001 S430 about a week ago when the rest feature stopped working and the heat went back to luke warm. I can confirm this was the problem from testing the pump with an ohm meter. Now, after a few days of use the problem is back. I would hope the pump isn't broken again and if it is could there be an electrical problem that will just break every new pump I put in? Also is it safe to assume there is not an air bubble in the coolant system because I still somewhat have heat? All of this being said, anybody know what the problem may be before I go back under the hood? All help is appreciated!

pghbenzo

Did you use a new or used pump? Could be if its used that it was on its way out. Also whats your overhead sensor readings? I have a bad overhead sensor and a bad pump I think. One may be causing the other, like the pump running to much and burning out because it thinks the heat in the car is 0 degrees. If this doesn't fix it I'm just selling the damn car at this point!

kraut56

You have to also check the duovalve function, as the problem may be there.

Check the stickies and search both forums.

There is also a "burp to bleed" procedure.

Gordon Cooke

It was used, but working when I put it in... I would hate to think it quit on me so soon. Ill test it, but I was looking to see what other possibilities where out there before I go through the same process for the second time in a week.
Im not sure what you mean by "readings" but I can say that the auto climate control seems to work well.. the car never got too hot or too cold when working.

pghbenzo

If you press and hold the rest button with the car running it will bring up a bunch of values, which are temp readings, flap levels, voltage etc.
Push up or down on the left hand temp switch to cycle through them. The second value labeled 01 will be you overhead sensor make sure it doesn't read 0,0

Gordon Cooke

Thank you for that tip! I never knew you could do that. My readings look fine so it seems that I'm just going to have to cough up the $170 for a new pump (not including the $40 I spent on the used one the first time around!).