S4 cluster woes

[4ringsinutah]

Alright so I have had my s4 for about a month, and power the past few weeks some problems have reared their ugly heads, I had a fuel line burst and a drop in psi, which I found was because the battery died and Apr reset to stock.....that is a fixed but now I have a new problem.

About a week after I bought the car, I noticed that the oil temp dial would work for about 15 seconds after I started the xar, and then drop to nothing and stop working. It would stay at 0 unless I turned the car off and on again, at which point it would show temp for 14 seconds and repeat same thing.

Well I flushed my coolant the other day and found her another problem..I was driving along fine and car was cool smack dab on the midline, well all of a sudden it started to shoot up all the way to hot, no matter what it did. Well I immiedetly stopped the car, checked coolant" it was low but I figured it was air bubbles and rebled the system. I let it sit for a bir, and turned it on and it went straight to hot again. Well I was really concerned so I opened the hood expecting steam, but nothing....I touched the manifold and it was not hot at all....so I chanced it and drove home to grab my obd2 reader. Well I plugged it in and the temp I was seeing was 87C after driving for 30 minutes with my guage pegged at hot....at this point I am feeling it has to be the guage as the ecu is reporting perfect temps across the board. Has anyone heard of a gjage failing like this? Do the ECU and temp gjage get their numbeers from the same sensor? Could this be a bad wiring issue or is the gauge cluster going bad? Thank you for any insite or help you can give!

[JVD]

Are you talking about two different gauges in your post? Hard to tell...

Oil temp AND water temp?

[rollerton]

Your OIL temp problem is the sensor in the bottom of the pan. It's actually sort of common, and they fail in that way sometimes oddly enough- I've had the EXACT thing happen.

Coolant temp also not very likely to be the gauge, more likely a sensor. Does it always peg hot now or does it only happen sometimes? Unplug the coolant temp sensor next time it happens and then check the gauge.

[Mad Cow]

The coolant temp sensor is actually 2 sensors in one housing, that's why they're 4 pins instead of 2. The cluster and ecu get different signals and basic obd2 readers only connect to the ecu. If you had vagcom you could check the cluster's temp reading, but it would be pretty safe to assume the sensor's bad since the gauges very rarely go bad so suddenly. It could also be a wiring issue though, never rule those out.

[getslideways]

When swapping the oil pan sensor ONLY use a Hella brand unit. Others are flaky or just outright don't work.

As for coolant, swap the sensor, lots of problems with the early sensors. Its a cheap and easy thing to try, so do that and see if all is well and happy again. Remember, the gauge cluster can only do what it is being told to do, so its rare for a gauge cluster itself to be the source of weird readings, its usually just getting weird info.

[4ringsinutah]

Ok guys, thank you for all the input i am looking into those issues now

so here is what i have traced down so far. I let it sit all night and then fired it up, went straight to hot and oil temp showing 260F......so obviously there is an electric gremlin hidden somewhere connecting everything. Well while driving ( i am monitoring ECU reported temp, so i know my car is running a cool 85-90C) the temp guage will randomly drop to C......and then suddenly my AC works again! Which i dont think i mentioned in my last post but when on H and Temp warning beeping, AC will not kick on. As i realize this is confusing lets summarize the symptoms
When Guage is on H
-Temp warning beeping constantly
-AC compressor will not turn on
-Car wont boost beyond 8 psi
-Automatic one touch windows dont work?
-Oil guage randomly stopped working one day, will come on for 15 seconds after starting the car and then nothing
-Low oil pressure light flashes randomly, but pressures tests fine when i test with an analog guage

When the car randomly drops to C all of these resolve and the car boosts straight to 17psi and AC is ice cold.
I have torque monitoring the engine temp and the highest recorded temp was 100C after HARD driving, and then it cooled right back to 85C


Where do i start based on these symptoms, i know that the AC and cluster are on the same circuit. Should i start with the coolant sensor and go from there? Full disclosure, i was dinking around with the resevoir the other day, i did move it to get to something underneith. Is it possible that i screwed the wiring?

I should also mention car is for sale haha, so i am trying to get rid of this gremlin before i hand it over to the new owner who ever that may be.

[4ringsinutah]

Update:

Unplugged the coolant sensor going into the resevoir and ran the car to see what would happen. As expected, the car started with the Temp warning light, however the coolant temp guage was possessed, it would hop around to "hot, Midline, Cold" at random intervals, but still keeps pegging to hot. Anyone ever experienced something similar to this? Thank you for any help you can give.

[getslideways]

Update:

Unplugged the coolant sensor going into the resevoir and ran the car to see what would happen. As expected, the car started with the Temp warning light, however the coolant temp guage was possessed, it would hop around to "hot, Midline, Cold" at random intervals, but still keeps pegging to hot. Anyone ever experienced something similar to this? Thank you for any help you can give.

the one in the reservoir is not the temp sensor, thats the coolant level sensor. The coolant temp sensor you are after is under the MAF tubing behind the head (there is a second coolant sensor on the opposite side head as well, but that is for the afterrun system). Try swapping or unplugging that one to see what happens

[vavJETTAw36]

Some cars will disable the AC if the car is too hot. Not sure if the 2.7t is one of them but it sounds that way. It looks like an obvious sensor problem to me. Those are cheap so just change it and see what happens. Like stated before, do not rule out wiring issues.


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[christianb5s4]

I had the same issue with my oil temp sensor as well as the coolant temperature sensor, they are common parts to fail or start reading erratically while they are on their way out and are cheap to replace. Do both at the same time, make sure you go OEM for both. Don't have to order from here, but this will give you part numbers for both:

https://www.ecstuning.com/b-genuine-...059919501akt2/

https://www.ecstuning.com/Search/1J0907660C/ES2636221/