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

[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.

[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 :)

[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.

[r4esh]

Test it by replacing the SENSOR with a resistor or ground the wires going to the sensor and see if the gauge moves. If it does not, it's your wiring and/or cluster.

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?

[Jean]

Test it by replacing the SENSOR with a resistor or ground the wires going to the sensor and see if the gauge moves. If it does not, it's your wiring and/or cluster.

[sohc12vm20]

No, I'm the OP with no solution yet.
To answer your question: You only need to ground the sensor if you're running it "inline" and its not threaded into the block. This would be the case if your sensor is the "T" style running through your throttle body coolant lines. If its normal and threaded into the block, then its already grounded by the block.

Ok, thanks.. My temp sensor is in the block and I seem to have the same problem, I work six days a week now and no time to tinker with it. I'd like to read what this issue is. Thanks again.

[e46s54dr]

Okay, so I'm now suspicious of the water pump. I'm going to take the upper radiator hose off tomorrow and see if water comes out when I turn the car on to confirm (unless someone has a better idea). But my thought on this is that maybe its not circulating and there is still air in the system / at the sensor. We'll see what my test yields tomorrow...

I'm still unsure as to why my needle wouldn't jump when I tried to ground the harness side wire. I'll try "e46s54dr" suggestion next. I don't think that's my issue but we'll see.

Anyone have a good suggestion of which / how to install an aftermarket gauge to test?

Even if your pump wasn't circulating water it would most likely read that its running hot and the needle would move around. If you do decide to re-burp your cooling system, try jacking the front end up in the air while you do it to help the air escape from the pockets. Good luck and let us all know how things go.

PS, Try to find another cluster to swap over to see if anything changes. That might be the easiest way to verify a faulty cluster.

[r4esh]

Sorry for this question, but I have the same problem. My temp sensor bumps up once and never moves.. My harness I know is fine and I labeled all my conectors, and my temp gauge worked fine before swap.. Am I reading correct but I have to ground the M20 sensor to the block?? I just didn't understand what I read.

No, I'm the OP with no solution yet.
To answer your question: You only need to ground the sensor if you're running it "inline" and its not threaded into the block. This would be the case if your sensor is the "T" style running through your throttle body coolant lines. If its normal and threaded into the block, then its already grounded by the block.

[sohc12vm20]

Sorry for this question, but I have the same problem. My temp sensor bumps up once and never moves.. My harness I know is fine and I labeled all my conectors, and my temp gauge worked fine before swap.. Am I reading correct but I have to ground the M20 sensor to the block?? I just didn't understand what I read.

[328ijunkie]

I doubt its the pump. Wiring issue or the sensor. If you want I can send you another, im still stuck on it being a wiring issue tho

[r4esh]

Okay, so I'm now suspicious of the water pump. I'm going to take the upper radiator hose off tomorrow and see if water comes out when I turn the car on to confirm (unless someone has a better idea). But my thought on this is that maybe its not circulating and there is still air in the system / at the sensor. We'll see what my test yields tomorrow...

I'm still unsure as to why my needle wouldn't jump when I tried to ground the harness side wire. I'll try "e46s54dr" suggestion next. I don't think that's my issue but we'll see.

Anyone have a good suggestion of which / how to install an aftermarket gauge to test?

[e30rapidic]

99% sure its the ground. If it was working and in fact had a big air bubble, it would still move a little. Although I have an S50 swap, I had my temp gauge AND fuel gauge drop to zero and stay there. A tap on the cluster lens did the same thing, made them jump but then they became really erratic. Turned out they were both ground issues. This was after I bought a new cluster board and ripped out some hair. Turned out to be an easy fix.

[drumad]

Sounds like your issue IS the ground. I had that issue the first swap we did. I had to wrap the sensor in wire and ground it to the block somewhere for it to work. Try it, let us know.

Awesome. I will try this upcoming weekend. I'm thinking my ground is probably just insufficient as its just a 16 ga wire going from the adapter to the block. I'll try it again. Good to know you have actual experience with it.

[r4esh]

Dammit I was looking for resolution here as I'm running into the same problem. I'm pretty sure I'm bled and am not overheating but I'm not going to drive her hard until I find a solution. I'm also running the aluminum inline adapter where the sensor is fed into the throttle heater line. Hopefully my ground from the adapter isnt the issue.

I've also done the same thing where I modded the harness vs using an adapter. I'm also using an m20 sensor.

Here's the inline adapter for anyone curious. http://www.zionsvilleautosport.com/s...de/OBDITSM.htm

Sounds like your issue IS the ground. I had that issue the first swap we did. I had to wrap the sensor in wire and ground it to the block somewhere for it to work. Try it, let us know.

[drumad]

Dammit I was looking for resolution here as I'm running into the same problem. I'm pretty sure I'm bled and am not overheating but I'm not going to drive her hard until I find a solution. I'm also running the aluminum inline adapter where the sensor is fed into the throttle heater line. Hopefully my ground from the adapter isnt the issue.

I've also done the same thing where I modded the harness vs using an adapter. I'm also using an m20 sensor.

Here's the inline adapter for anyone curious. http://www.zionsvilleautosport.com/s...de/OBDITSM.htm