Temp gage and light issue
 

My brother-in-law was driving my (32k miles) 2003 Boxster S today. The Boxster drove flawless as usual up the long climb to the summit of Pikes Peak, but on then on the 19 mile, 7000 foot decent, the temp light started flashing and the temp gage was pegged all the way to cold. Nothing seemed to be wrong with the car, but the gage didn't appear to be working and the warning light was flashing.
After sitting on the side of the road for a while, with no other issues perceived, he started driving it back to my place and after several miles, the gage started working again and the light went off. Temp was normal, as it was before the gage stopped working. Right now it's working like normal again. I searched the forum but didn't see this same issue. Anyone seen this problem before?

I would guess pressure change related due to elevation, but just a WAG.

Got a code scanner? Be interested in seeing if anything was logged.

Did you check the coolant tank to see what the level was?

A few years ago I drove up pikes peak, it was an amazing drive up and down, only wish I wasn't in a crappy rental van at the time.

This is a real puzzle. Please post the cause if you find it.

If the coolant level was normal, I would guess a bad sender unit.

Checked the coolant level when the car was cold this morning and it was just below the low line, but still well within the site glass. Took about 12 ounces to fill it half way between the full and low lines.

Drove the car this morning and everything was normal.

I was wondering if it may have cooled down below normal operating parameters on the decent and maybe the computer shut that system off or something. I don't think I'm going to bring it to a mechanic unless it does it again. Bothers me though since the car never misbehaves like that.

My temp light started flashing when the coolant was at the low mark on the tank, after adding about 8 oz of water to bring it back into mid range the light went out, only happened once. I'm thinking the low coolant sensor is very sensitive, not a bad thing.

maybe the altitude had an effect on the level

Hi!! I'm interested in this also!! My 2001 Boxster is doing the same exact thing! Nothing else seems to be wrong. Light flashing and temp reads all the way to left. Help! Thanks.

Mine has not done this again since my first report. Drove it to Aspen and back yesterday, a all day trip, and everything was fine. I don't think I'm going to worry about it unless it happens again.