Coolant temp. gauge is a LIAR!

[Sagaris]

My gauge cluster is tripping out a bit..

Everything in the cluster is fine with the exception of the BRAKE LINING light which illuminates as it wishes and the temp gauge which will be indicating that I am at operating temperature, then at random it will jump up to 3/4. Both glitches are independent of eachother (they can happen separately or together) and they can be fixed for a few minutes by tapping on the face of the cluster.

What can you guys tell me about this? Is this the batteries needing replacement or is this a sign that the whole SI board needs replacement?

What are your recommendations on fixing it? I am no stranger to ripping clusters apart and reparing electronics if it is something that can be repaired with some solder or wires.

I am planning on just pulling the bulb for the BRAKE LINING light.


Thoughts?


PS. I am not sure if it has any relation or merit, though I have noticed that when i shut my car off , the tach jumps up a few hundred rpm about 4 seconds after the car is off. I thought I would mention it in case there is some relation.



>I searched some more and found this: http://www.s14.net/forums/showthread.php?t=38562&page=2

which says the gauge "dancing" can be caused by bad wiring on the temp sender or a bad ground on the back of the cluster, though mine can be fixed via tapping so it doesnt seem that it would be the wiring in the engine bay.

>This also: http://www.m42club.com/forums/showthread.php?t=7086
Someone commented on tightening a nut on the back of the cluster (presumably part of a printed circuit that is held on by a nut)

[jeffesaurusrex]

Take out the cluster, wiggle all the connections and make sure they are all good and tight. You can also use a multimeter to check all the connections on the boards for continuity. If any of them are bad you just heat up the solder with an iron and let it reflow. In a 20-25 year old car sometimes the solder joints go bad.

Otherwise, replace the cluster.

[khalild]

There are several possibilities IIRC, take the easiest routes first. First make sure your coolant was properly bled/ changed. If you never drained it from the block, chances are you should. (while your coolant is out change the thermostat to a low temp one)

Next Take out your cluster, (pretty easy to do, all you need are a 22mm socket, marker, and a phillips screwdriver. There are two grounding nuts that may need to be tightened or replaced.

If tightening those doesn't work, replace the sensor. Go to one of the various online stores such as pelican parts and order a new sensor.

One of these will normally fix that problem. The first fixed mine. Whatever one of these you haven't done, you probably should do. You can get all of what I said done for under 100$ and 2 hours.

[DJB]

Remove the cluster and re-flow the solder where the gauge's mounting stud goes through the circuit board. The solder cold flows from the pressure, resulting in bad contact.

While it's out, re-flow the solder around the larger resistor that's part of the brake lining circuit. Do a search -- you'll see pictures to help locate the resistor.