blink

On my way into class this morning I noticed my temp gauge was cold (on first white mark, not resting like when the power is off). After a bit I noticed it rise back to normal, then ten minutes later, back on first mark. Oil temp remained the same the whole time, I think it sits at 225. It's my understanding that there are 2 CTS on the 30v 2.8, one on the lower coolant hose, and the other on the right rear of the engine. Does anyone know which one influences the gauge cluster? It may be time to splurge the whole $40 for both of them, and donate mine to the smithsonian.

SloopJohnB@mac.com

Cheap enough to check the connectors on both sensors. Unplug one and see if the instrument panel changes. IIRC the one on the rear of the engine is the CTS that the ECU and the cluster use.

The one on the lower coolant hose isn't the engine coolant temperature…it's the temp of the coolant going into the engine from the radiator. I believe it controls the electric coolant fan. At least on a 1998 A6 2.8 according to Bentley.

blink

Hey, thanks Sloop. Thats what I needed to know. The rear CTS is what I'll end up replacing. Local parts store has it for $11. Who would have thought. Thanks again.

blink

After replacing the rear sensor, I still have the same symptoms. May be looking at a malfunction at the gauge.

jcman

If you have Vagcom/VCDS you can check all cluster gauge range functions.

tenspeed

Your intermittent fault sounds to me like a bad electrical connection. I would start closest to the engine since that's a hot area and subject to vibrations.

blink

I am without vagcom right now. I keep putting off getting it, my issues are never really that baffling. Mostly vibrations, leaks, or the average stuff. Replacing the CTS clip with a new one today (meyle- from napa autoparts, .65 cents) i'll double check the wiring then. Drives me nuts not being able to monitor coolant temp, and it's only been a few days.

blink

After installing a new clip, I found that the plug on the sensor was not completely clicked in. After doing so, everything is back to working normal. The gauge is back to the the exact center reading, where before the malfunction it was a tad to the right. Woo Hoo! Thanks all for the help!

SloopJohnB@mac.com

There ARE connector kits available for every connector on the car, they're just difficult to find unless you get the p/n before it disintegrates or can get it from the dealer.
For example, I keep a couple 4.2A6Q coil connector repair kits…but the kits aren't always user friendly to the extent of simply releasing the existing pins from a disintegrated connector body and plugging them into the new body!
The last time I did this a few weeks ago the kit had different female connectors in the connector body and I had to cut the old wires and solder the new pigtails to the old wires to the chassis cable. But the new connector snapped sweetly onto the coils. BTW…use dielectric grease on the coil body/connector…it helps to get them off the next time.
I even bought the connector disconnector, AKA VAG Connector Removal Tool….works incredibly better than a screwdriver which generally destroys or damages a heat-hardened connector.

It's worth it's weight in silver, at least.

002916SCH01A - VAG Connector Removal Tool - ES#2628676

Prospeeder

Your sure the thermostat isn't just stuck open and the coolant temp is fluctuating all over from not being controlled? Oil temp is much much slower to respond to coolant temp changes.