Was your first replacement OEM? Aftermarket thermostats suck. The thermostat housings on the V engines is behind the timing belt and a serious pain to get to. I just replace it along with everything else during a TB change.

 

Yes it was. I have to get under my car to change it, don't have to remove anything else though.

 

+1 for OE - but I put an OE water pump in mine when doing the timing belt and it leaked 4 months later...

 

It was OE. See my last post.


The new OE thermostat arrived today. Will put it in Sunday, hopefully it fixes the problem.

 

The new OEM thermostat was installed today. Temp gauge still reads the same though. Only makes it to the first mark. It seems like it thinks that's the middle for some reason. I have heat, no CEL and the car seems to run just fine. All this seemed to happen after I replaced the CTS which was giving me a CEL but causing no problems.

Any ideas on what could be happening?

 

Use an infrared temp gun to verify actual engine temp and verify with vagcom. (To see what the DME and dash are seeing)
No heat could mean air at the heater core, not bled enough.
What brand sensor did you get? Green plastic right?
Sounds like maybe a bad sensor or connection.

 

The CTS has two temperature outputs - one which goes to the ECU, and the other goes to the instrument cluster. It's possible for one of those to be bad while the other is good.
This can be diagnosed with VAG-COM / VCDS.

 

I don't have an infrared temp gun lying around sorry. Don't have vagcom either (I know I should)

I said I have heat when I turn it on.

I got an OEM sensor. I use OEM always if I can find them, it was green. Don't see how the sensor could be bad as it would throw a CEL that's how I knew it was bad. The CEL went off on its on the day after I replaced the sensor.

 

Possibly not a strong connection? Because the dash does read some temp so it can't be a completely bad connection otherwise the temp on the dash would never move, correct?

Looks like I need Vagcom.

$6 cable from eBay correct? Don't you have to pay for the software though?

 

Just read the whole thread. I think this is what you’re seeing in a nutshell:

• Heater is good.
• Gauge reads too low right after a CTS swap.

So to me:

• Stat is probably doing its job if the heat is good.
• The only reason to suspect a bad stat is if you absolutely trust the gauge.
• If the gauge went bad after a new CTS, why do you know it’s not the CTS providing bad data to the gauge? As MetalMan says, the CTS is what sends the temp reading to the inst. cluster.

So it seems to me you have far more reason to question the new CTS than the stat. Go the the dealer and get the right OEM CTS for your VIN#. It will cost you $10 more than Rock Auto, but you will be able to take it out of the equation. Again, if your heat is good, your stat is not stuck open.