Temp gauge goes down when heater turns on

[krisko]

Everytime I turn my heater on my tempature gauge goes 1/4 lower on the guage. Also my car takes long to heat up. I have no leaks and I my coolant level is good. Is this my thermostat?

[MmmBoost]

sounds like your thermostat

I had debris in my engine block coolant passages that kept getting into my thermostat and not allowing the valve to full close which allowed coolant to the radiator. My car would take forever to warm up and sometimes just wouldn't. I changed the thermostat and it didn't solve the issue. I finally found out what the culprit was when i inspected my old t-stat as well as when I tore down the block to do my engine build.

[A4Maine-iac]

^x 2 on thermostat. Had same issue with mine.Took about an hour and all was good!

[s6sputnik]

Everytime I turn my heater on my tempature gauge goes 1/4 lower on the guage. Also my car takes long to heat up. I have no leaks and I my coolant level is good. Is this my thermostat?

It is probably your thermostat, but do keep in mind that it is the coolant that is used in your heater so things change once you turn it on! I would check your coolant level and keep your eye on the gauges for a few days!

[rawkey]

$130 for thermostat at the dealer
get some G12
replace the Jplug part# 06B-103-033-A since you're in there
http://www.audizine.com/forum/showth...at+replacement

[onceover]

I had the same problem last year and replaced the tstat ant everything was great. This year its not as bad but still cools off a bit while idling with the heat on.

Could a faulty coolant temp sensor be affecting how the tstat opens and closes?

[alexza4]

yes, def. thermostat

[rawkey]

I had the same problem last year and replaced the tstat ant everything was great. This year its not as bad but still cools off a bit while idling with the heat on.

Could a faulty coolant temp sensor be affecting how the tstat opens and closes?

From my understanding the CTS on the coolant flange sends signal to ecu for temperature monitoring and CTS on rad contols fans.

[krisko]

Update.* Im about to change my t-stat but now when I first turn my car on my radiator fans both turn on for about a 10 minutes then will shut off when the car starts to warm up? Whats causing this issue is the temp sensor hooked into the thermostat?