HELP e30 m3 s52 swap - Runs but - Coolant Temp Gauge not working... toltally stumped.

[Jalves619]

Are some of the parts interchangeable between clusters? You're not likely to find another full e30 M3 cluster for under $350~$400. The m20 FSM may have the correct resistance values for that coolant sensor. Grab one/a few within that range.

[Jean]

This is a great test, but for me when I tried grounding the sensor nothing happened with the needle. MY test light DOES light up though if I stick one end in the connector and ground the other end. So I know the wire is getting its power. WHICH leads me to think the cluster is the issue. Now I just need to find someone in Tucson, AZ with a cluster I can barrow I guess..
If I were to try a resister on it, what resister would I use?

of the value within the range of the sensor from bentley :)

[r4esh]

Okay so small update: I only get like an hour every couple of days to stab at this unfortunately... BUT I disconnected the upper radiator hose and cranked the car to test the water pump. Water came shooting out, YAY. With no thremostat in I blew through the coolant tank and the water was moving, so I have good circulation too. So now that I know my water pump is good, thermostat is good, and that I have good circulation I'm a lot less scared to run the car for a longer period of time. And thus I'm back to testing the gauge / temp sensor... Stay tuned.

[DTM190]

Yes it's an m20 sensor. And it was re-threaded by Market Motorworks to fit into the old throttle body coolant line hole on the block for the swap.

Out of curiosity why was this done instead of replacing the M50 gauge sensor with an M20 sensor?

[r4esh]

Out of curiosity why was this done instead of replacing the M50 gauge sensor with an M20 sensor?

You didn't read the whole post. This is an s52. So you must use the obd1 m20 sensor for my application. Just so you know.

[DTM190]

Gotcha

[r4esh]

New update. I have a new temp gauge on the way which I will install Monday and share result. Here's some more insight:



^ I know we all love reading ETMs... so I highlighted our focus in red. I'm not sure I understand this. Apparently the temp sensor goes right to the gauge. No fuze in between? Or is the whole cluster on a fuze? IT draws power from "service interval process" ? I was hoping this would give me some insight to other places to check for an issue, but it seems like the issue can only be "sensor, gauge, or wiring". I think we can rule out wiring at this point.

[Sputnik]

Forgive me if its already been covered, but have you check the resistance at the sensor to see if it was faulty from the beginning?

[Jalves619]

Could dead SI batteries be causing issues? I've heard of them throwing off the tach and other gauges before. Since the temp gets power through the Service Interval Processor it seems possible. Have you checked for power at C5 Pin 1 and for a ground at C5 pin 12?

[Jalves619]

http://www.r3vlimited.com/board/showthread.php?t=230238

Oil light turns on after running for a while still? Look at post #4

[r4esh]

Okay.. Just to revive this for a moment in case someone else with the same issue stumbles upon it...

I finally got a chance to pull the intake. I indeed had the oil pressure wire plugged into the temp sensor... fixed that.. went through all other connections multiple times, and the ONLY left over connector was a "2 wire" plug... confusing no? I swear I quadruple checked everything. MY harness came from a 525i. Does anyone know if there is a variation for that connector instead of the single wire? I know its strange, but I went through it OVER and OVER and everything else matched the ETM and the DOHC wiki wiring with this connector being the only thing left over.

SO my solution (haven't put it all back together yet to test this) - I'm going to try the 2 wire plug. If it doesn't work I can a backup wire of my own from pin 4 to the sensor.

Either-way I will report back.

[328ijunkie]

The temp sensor plug is 2 pin even though the e30 only uses one. Have you gotten your replacement sender in?

[r4esh]

The temp sensor plug is 2 pin even though the e30 only uses one. Have you gotten your replacement sender in?

Well that settles it then. I haven't gotten it yet, I'm going to piece the intake back together tomorrow, if all works well ill send the replacement back right away. Thanks again for sending me one.

[Mr.SWISS]

Do we not have anyone local that can go assist?1?

Fly me down I'll fix it.

[328ijunkie]

Pics of a customers conversion harness for reference:



I remove the unnecessary ground from the harness completely all the way from here to the X20:




Jeez my hands are nasty.