SPi temp needle pegged on hot and doesn't move

[davewillner]

Hi guys, hey just picked up a 96 JDM SPi w/28K miles.  Pretty well sorted, runs, drives, idles fantastic except that the temp gauge needle is buried on hot all the time and doesn't move at all, on or off, cold or hot. I don't have a fault reader yet, looking for some advice on one, but right now looking to see where I should start other than ripping off the in the inlet manifold to replace the temp sensor, which I sense is a PIA? I guess getting the fault reader asap is the priority...What else tho should I check at this point?  Appreciate the help, txs 0

[MiniDave]

Hi Dave, welcome to Restoration Mini!

My advice is to unplug the sensor, if the needle doesn't move the problem is probably in the gauge. If it drops to cold again, the problem is either the sensor or the wire that goes to the sensor is shorted to ground.

[MPlayle]

To add to what has already been said: the wiring goes from the sensor to the ECU, then from the ECU to the gauge.

You may need to check several connections to be sure there is not a short or crudy connection.

[MiniDave]

That's the problem with SPi and MPi cars here , unless you have access to the software tester you're mostly guessing. But I doubt a dirty connection would give you full scale, I think that would take a short......

[davewillner]

So I'm picking up the diagnostic 3 pin/USB lead on eBay and will download the app. Being a new owner, would rather do anything than pull the intake manifold right now.  Two questions, will the app be specific enough to determine the exact issue?  And wouldn't the car run erratically if the temp sender was at fault, I mean it starts, runs, and idles really perfect?  Thanks 

[tmsmini]

Does this car have a coil pack or a distributor?
I dont have an SPi but I know some cars have two 3 pin connectors, one white and one green. I am pretty sure you need to use the white connector.
I am guessing you will be using the RoverMEMS software:
https://rovermems.com/

It provides a full data dump of the ECU, so there is information not used in the Mini implementation.
You should be able to see the temperature and tell if the sensor is providing accurate data to the ECU.
I am guessing this uses the Nippon Seiki gauges which use a electronic voltage stabilizer built into the circuit board, not sure a faulty voltage stabilizer would cause your problem though.
The Mini Forum has a post on fixing the stabilzer.

[MiniDave]

I've repaired a couple of these temp gauges, but usually they're dead cold - which is due to a small lead inside the gauge that breaks at the solder joint. Never had one go full scale unless the wire is shorted.

I agree, seems like if the ECU is getting the wrong info the car wouldn't run right. I'm betting on a short in the wire from the ECU to the gauge.....might be difficult to find, but the wiring harness in these cars is not THAT large, or long.

Be sure to let us know what you find!

[tmsmini]

Here is the article on the VS in the Nippon gauges:
https://www.theminiforum.co.uk/forums/index.php?showtopic=146533
but I dont think it applies as your fuel gauge would act up as well.
The wiring in these cars is getting old and the insulation they used is not as good as the 50 year old wires, so I think Dave is on the right track

[tmsmini]

Useful guides:
http://www.tmsmini.com/cooper/pdf/RCL0193ENG_Rover_Mini_Workshop_Man_MPI.pdf

http://www.tmsmini.com/cooper/pdf/RCL0194ENG_Rover_Mini_Circuit_Diagrams.pdf

http://www.tmsmini.com/cooper/pdf/RCL0426ENG_Rover_Mini_Wiring_Diagrams.pdf

96 was a changeover year, so this might apply:
http://www.tmsmini.com/cooper/pdf/AKM7169ENG_Rover_Mini_Repair_Manual_92-96.pdf

[MPlayle]

tmsmini: Can you double check the links for the pdf files in your last post?  The website does not resolve correctly.

[tmsmini]

That should fix it, left off the .com for the website.