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b5a4erik
03-15-2015, 01:46 PM
Hey all,

'99 A4 FWD 1.8T AEB

So I got a CEL for the coolant system, upon research I decided to change my Coolant Temp Sensor (CTS).

Now the CEL is gone, but my Coolant Temp Gauge is acting strange:

- If I start my car then immediately drive for say, half an hour, the gauge doesn't move at all, the needle stays at the bottom.
- If I then shut my car off, let it sit for a bit, start it up again, the needle will have moved, the gauge reading either partially up to temp or fully up to temp (middle of the gauge).

- If I start my car then let it idle for say, half an hour, the needle will move up till the gauge reads up to temp.
- However, once I start driving, the needle drops, slowly but surely until it hits the bottom.
- If I then let it sit and idle, the needle will once again move up till the gauge reads up to temp.

What's going on with my car? [confused]

adam044
03-15-2015, 03:21 PM
Did you get an OEM temp gauge?

maxman
03-15-2015, 04:15 PM
Hey all,

'99 A4 FWD 1.8T AEB

So I got a CEL for the coolant system, upon research I decided to change my Coolant Temp Sensor (CTS).

Now the CEL is gone, but my Coolant Temp Gauge is acting strange:

- If I start my car then immediately drive for say, half an hour, the gauge doesn't move at all, the needle stays at the bottom.
- If I then shut my car off, let it sit for a bit, start it up again, the needle will have moved, the gauge reading either partially up to temp or fully up to temp (middle of the gauge).

- If I start my car then let it idle for say, half an hour, the needle will move up till the gauge reads up to temp.
- However, once I start driving, the needle drops, slowly but surely until it hits the bottom.
- If I then let it sit and idle, the needle will once again move up till the gauge reads up to temp.

What's going on with my car? [confused]

Your thermostat is stuck open I just had the same problem. Your gauge is accurate because when you are driving the coolant is always flowing and is cooled by the air passing through the radiator. The reason it reads warm after you shut it off and come back a few minutes later is because the hot engine block heats up the coolant while sitting.

b5a4erik
03-15-2015, 05:19 PM
Did you get an OEM temp gauge?

Looking back, I could've been a little more clear when differentiating between the sensor and the gauge.

Which I say because I think in your question you meant: Did I get an OEM sensor? To answer that question: No, I don't think so - something I am aware may not be preferable in some cases, but in this case I'm fine with.

As for my gauge, it's the stock coolant temp gauge, part of the rest of the guage cluster, with the speed and rev gauge and what not.

b5a4erik
03-15-2015, 05:21 PM
Your thermostat is stuck open I just had the same problem. Your gauge is accurate because when you are driving the coolant is always flowing and is cooled by the air passing through the radiator. The reason it reads warm after you shut it off and come back a few minutes later is because the hot engine block heats up the coolant while sitting.

Thanks for the reply. Looks like another project, more work to do but hey, I'm making my car better and I'm happy about that. [up]

adam044
03-15-2015, 07:36 PM
Looking back, I could've been a little more clear when differentiating between the sensor and the gauge.

Which I say because I think in your question you meant: Did I get an OEM sensor? To answer that question: No, I don't think so - something I am aware may not be preferable in some cases, but in this case I'm fine with.

As for my gauge, it's the stock coolant temp gauge, part of the rest of the guage cluster, with the speed and rev gauge and what not.

Yeah sorry I meant sensor. Just asking because I got an aftermarket sensor and it was junk, my engine light went off but the gauge still read wrong. Fixed my issue by getting an oem sensor.

b5a4erik
03-15-2015, 08:12 PM
Yeah sorry I meant sensor. Just asking because I got an aftermarket sensor and it was junk, my engine light went off but the gauge still read wrong. Fixed my issue by getting an oem sensor.

Hm, makes me think. Was your gauge acting similarly to mine? Or just always reading cold?

adam044
03-15-2015, 08:39 PM
Hm, makes me think. Was your gauge acting similarly to mine? Or just always reading cold?

oh man, uh to be honest I cant remember. I think it always read cold but I'm not sure because I've done my thermostat twice and sensor twice so who knows.

I'd say try an oem sensor, it's easier than the thermostat. That's what I would do, because I've been there.

b5a4erik
03-15-2015, 10:04 PM
oh man, uh to be honest I cant remember. I think it always read cold but I'm not sure because I've done my thermostat twice and sensor twice so who knows.

I'd say try an oem sensor, it's easier than the thermostat. That's what I would do, because I've been there.

I hear ya, appreciate the input yo.

crazy tarzan
03-16-2015, 06:48 AM
I'm having the same issue, and also changed the CST. I'll be doing the timing belt in the next week or two, and have a new thermostat as well. I'll post back with updates after putting new thermostat in.

b5a4erik
03-16-2015, 08:08 AM
I'm having the same issue, and also changed the CST. I'll be doing the timing belt in the next week or two, and have a new thermostat as well. I'll post back with updates after putting new thermostat in.

word, sounds good. [up]

adam044
03-16-2015, 09:06 AM
I hear ya, appreciate the input yo.

No problem home biscuit

b5a4erik
03-30-2015, 04:59 PM
So I went ahead and got a new thermostat, considering it the next step before potentially having to buy an OEM temp sensor, put it in, and it looks like problem solved [up] Thanks everyone for the posts! [drive]

adam044
03-30-2015, 06:59 PM
cool beans yo.

crazy tarzan
04-06-2015, 07:39 AM
Just did timing belt, water pump and thermostat.

Issue is now fixed, temp gauge sits right at center--and my heater finally works well!