[QUOTE=KMCG35X;5266098]Wow...I just had this problem. Mine was even worse. It was indeed a hot day (mid 90s). I started the car and the tach jumped up as the engine turned (like normal) and then slowly dropped toward around 1500rpm (the engine did not sound like it was running that fast). As I started to drive the car the tach was showing 3000rpm when I was just putting along at 35mph in D. (I knew this was wrong). Stopped at a light and put it in neutral to find 2000rpm showing at idle. Drove a few more miles home (now reading 4000rpm in put-put speed), and turned the car off to watch the tach STOP at 2000rpm...rats!


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I just had this happen to me today. Very hot day (no where in the office to park in shade) temp gauge read 109. Tach was reading about 1000 more than normal. Tried manual shifting to see if it would clear up, but it didn't.

Pulled over and turned off ignition to try to reset, but that didn't work either.
When off tach stops at 1,110. Drove home and again, w/ignition off, it's at 1,100. I'm going to take picture of this to show dealer.

BTW--I've noticed when I start mine up, the tach/speedometer does not flash up then fall down. Are they all supposed to do this? (mine's an '07)

 

Well, within 30 min of pulling into the garage, the tach had fallen back to 0 without the ignition being on.

I tested the gauges per above and mine showed the following:
tach 1800
spedo 35 mph
temp 50%
fuel 50%

Does anyone know what these readings mean?

 

I'm sure the tachometer isn't really broken...I had mine replaced, but before it was replaced, this problem only occurred in hot weather, but returned to normal after cooling down.

I think this is a manufacturing defect, which causes some metal piece inside the tach to expand in hot weather...or maybe electrical issues. Try to see if the dealer will replace it and test it again to see if it has the same problem.

 

There is a reset for the guage cluster. With the ignition off, press and hold the trip reset button, then turn the key on and continue to hold it. When the odometer blinks let go of the button. Press it again and reset will appear. The guages will go nuts and come back to zero. If the needle drops under zero or if this does not fix your problem, then replace the cluster.

 

^^ That's an interesting share. Thanks!

 

That is interesting on the reset.
For my update this issue happened again last summer a few times only with excessive heat. Did not repeat over winter/spring. With the heat of this summer it happened a few more times.
I took a video of it while driving then shut off with needle falling to about 1800 with ignition off. Showed this to dealer who said they never heard of this problem.
They replaced the cluster under extended Elite warranty last week. Saw 107 temps this week and no issues thus far.

 

I park outside and I just had this happen today for first time (thanks heatwave!!!). Freaked me out till I found this thread!

Will a sun visor stop this from happening? I don't use one, but will if it will help. Is my tach damaged as a result of this or will it eventually stop working if I keep parking my car in uncovered parking?

I can't believe this is actually an issue...

 

Try using the reset procedure above. If all else fails, then park it in a cooler area. Mine was never the same again when the interior is hot. I've had the cluster replaced by the dealer and no problems since, even in the heat.

 

I'll definitely give the reset a try.

Hoping not to have to go the cluster replacement route. We will see what happens...

 

Just wanted to update this thread.

I have not seen the issue return since it has cooled down a few degrees. I never performed the reset and I just waited till it got cool later on in the day.

I went out for a drive and my tach was working normally again. My guess is this is definitely a heat issue.

 

The reset will fix it right off the back if it's a heat related issue. Or you can wait for it to cool down and it should correct itself. If it's not a heat related issue and the reset does not work you will have to replace it, unless it doesn't bother you. I don't know if a sun visor will help. I now park mine next to a tree at work so the shade cools the car in the afternoon.