In the last few weeks I've noticed the ambient temperature readout on the dash of my 97 E300 is all over the place. While in the car today, (it's currently @ 75 degrees in Atlanta), the temp readout showed anywhere from 34 degrees to 79 degrees. Some of the time it goes out all together. I just had a new alternator installed and the battery is only about 2 years old. Not sure if a weak alternator could cause such an issue but I thought I'd just throw that in. My a/c also seems to surge at times, blowing at a steady rate, then suddenly at full blast, even though the outside temp nor the driving conditions hadn't changed. I'm thinking this may be a completely unrelated issue or are the 2 tied together? I have read threads regarding a blower regulator issue that the w210's are prone to. I assume this is just that issue. Doesn't really bother me that much. I'm really more concerned about possible electrical issues in the dash that the ambient temp readout is an indicator to. Thanks for any advice you can offer.

PS-With the help of this forum, I have replaced both fuel filters, the a/c cabin filters, and the driver sideview mirror with great success, all while being very new to the DIY Mercedes Diesel world. This forum is an incredible wealth of information.

__________________
'86 560SEL-108k,Sold Mar. 2000
'95 Landcruiser-113k,Totalled Aug. 2001
'92 Mazda Miata-22k,Sold Apr. 2004
'89 560SEL-31k,Sold Mar. 2005
'95 E300D-121k,Sold Dec. 2005(Mistake)
'95 BMW 740iL-26k($$ Pit),Sold May 2006
'06 Jetta TDI-8k,Sold May 2007(For MSRP!)
'97 E300D-123k,Sold Jan.2009

I am not an expert but I have done a little investigation on my E300 AC system. I think the ambient readout is read by the AC system as part of its operation. Does the fan speed change correspond with the ambient temp changes?

__________________

Muleears
'07 E320 Bluetec 133K my DD
'04 Jaguar XJ8 VDP, 34K
'10 Hyundai Accent 60K Grocery Getter
'02 VW Golf soon to be on the road again
'97 E300 Diesel Son's DD
'61 VERY tolerant wife

Hampton Roads, VA USA

Gone but not forgotten:
'67 250S 95K
'86 300SDL
'87 300D Turbo, 364K! R.I.P.
'98 E300 Turbodiesel, 213K
'02 S420, 164K
'01 Prius 138K

It's really hard to say. It does seem to corrolate to some degree but I'll need to take it for another drive and really pay attention. I can say that the a/c does continue to work even when the readout goes black(which can be for as long as 5 minutes). It does seem, however, that when it reads 75 degrees plus, it's cranking, and when it dips down into the 60s, 50s, 40s, fan speed really slows down. I can also say that I really only started to notice this fan speed surging in the last few weeks when the temp readout started going crazy, but keep in mind that's an observation/diagnosis from a novice DIYer. I'll head out for a drive and reply again later.

__________________
'86 560SEL-108k,Sold Mar. 2000
'95 Landcruiser-113k,Totalled Aug. 2001
'92 Mazda Miata-22k,Sold Apr. 2004
'89 560SEL-31k,Sold Mar. 2005
'95 E300D-121k,Sold Dec. 2005(Mistake)
'95 BMW 740iL-26k($$ Pit),Sold May 2006
'06 Jetta TDI-8k,Sold May 2007(For MSRP!)
'97 E300D-123k,Sold Jan.2009

After about an hour test drive and really observing the 2 issues closely they seem to be unrelated. Any abnormal fluctuations in the a/c blower don't really seem to corrolate with the temp readout going up or down or out. Looks like I've got 2 separate issues to look into.

__________________
'86 560SEL-108k,Sold Mar. 2000
'95 Landcruiser-113k,Totalled Aug. 2001
'92 Mazda Miata-22k,Sold Apr. 2004
'89 560SEL-31k,Sold Mar. 2005
'95 E300D-121k,Sold Dec. 2005(Mistake)
'95 BMW 740iL-26k($$ Pit),Sold May 2006
'06 Jetta TDI-8k,Sold May 2007(For MSRP!)
'97 E300D-123k,Sold Jan.2009