Temperature gauge concern

[slabadie]

I have a 2002 325ci convertible with 235,000. I have own the car since August 2016. The temperature that past several days have been way below zero at night. This morning it was -9 degrees. After I warmed up the car, I noticed that the temperature gauge was to the right of center slightly. The gauge has always been straight no matter how cold or hot outside. I checked the coolant temp when I got home and it was 185 degrees. The normal operating temp has always been 206 degrees. So is this just because it is so damn cold outside or is there something to be concerned about?

[MarcoZandrini]

Hard to tell. My suggestion is to gently drive the car and monitor the OBC readout of the temperature. Drive the car at highway+ speed for at least 20 miles to give the BMW goddesses some exercise.

[slabadie]

I took the car for a 50 mile round trip drive. The needle didn't move any farther to the right. The average temp for the round trip was 204.8 degrees at 65 MPH. Climbing a hill at 70 MPH the temp rose to 207.5 degrees. On the flats the temp dropped as low as 199.4 degrees.

On the way back I ran diagnostics using Carly app for BMW. I got an error code of 00001E (AUC heating / air distribution switch). Any chance this has anything to do the the needle moving to the right?

[Raddee]

Your thermostat may be sticking 'closed'. Any record of it being replaced and if it's aftermarket or OEM?

AUC heating switch is part of the HVAC system so probably not related. The engine controls it's own temperature regardless of the climate control.

[slabadie]

I replaced the thermostat housing with thermostat in summer 2017. I believe I bought it from Advanced Auto.

[MarcoZandrini]

Bingo! We have our “winner”! Never buy aftermarket cooling system parts! Never! The cooling system is the E46’s Achilles heel. Did you buy other aftermarket cooling system parts? You need to replace at the very least the aftermarket thermostat. Go to FCPEuro and buy a Whaler thermostat. You really should replace any other aftermarket cooling system parts with parts that are made by the suppliers of cooling system parts.

[slabadie]

That is the only after market part that I bought and stinalled, but I had the water pump replaced and installed last year by my mechanic. I have no idea what brand was installed.

[MarcoZandrini]

Ask the mechanic what brand of water pump was installed. The only brands of water pump that go in a bimmer are Saleri and Graf.