Temp Gauge doesn't move - Sorry for another thread on this!

[floatinghead]

I know this topic has be covered in lots of different ways, and i've reviewed a number of posts on the FAQ, but I still don't have this working.

So my temp gauge for a while was a bit spotty and would start out dead and then kinda "pop" up after a bit of driving.  I recently completed a front subframe rebuild and now the temp gauge does not move.  Fuel gauge  and all others are fine.

 

Things i've done:

1. Cleaned up ground on VR - sanded connector, screw and fender ( as i had painted wheel wells while subframe was out)

2. Checked Temp Sender:  I have continuity from brass connection to aluminum manifold.  Also checked resistance from connector to manifold and I get a change in resistance as it heats up and cools down. delta of a few hundred ohms.  So it appears to be doing its job?  

3. Wire Continuity: removed instrument cluster and wire appears to have continuity. I didn't pull wire from 12 pin socket, but stuck probe inside the pin 11 connector and to the wire end my sender.  

4. Instrument grounds: PO installed a long clean lead from 2 nuts on instrument panel to a clean spot on the body.  I checked continuity through these wires and they appeared solid.

5.  Tried to "mockup" a new wire lead.  Ran a wire from the sender and tried to connect to the pin on the instrument panel with a clip.  Not sure this was valid or not to test, but didn't get any movement in the temp gauge.  Also tried to slide a wire inside the pin on the connector, but didn't feel confident that was effective.  

 

Things to check?

1.  battery ground: relatively new ( though with some corrosion on braided cable at neg lead) that attaches to block and a spot on battery tray.  should this move to the body of the car?  wasn't sure if the tray was a good spot.

2. remove sender and clean connection at aluminum to brass interface?

2. Saw a write up by Mike Self to strip the wire back a few inches back from the 12 pin connector and temporarily solder in a wire to see if that works.  My "test" as done above may have not been a good enough connection...?

 

Any other thoughts?  

 

[PaulTWinterton]

Is the needle pinned at the top or bottom?  If it's at the top that means no ground connection.   At the bottom... I would suspect a bad gauge. 

[calw]

Not a direct answer, sorry,  but... 

 

I'm in the middle of rewiring the entire car.  I am using new wiring as much as possible, but the special connectors have to stay. 

 

So far, every connector pair that I've checked hasn't made me happy - gunk and grime mostly.  I plan on reheating any soldered connection that needs to stay that's accessible, and using Deoxit when re-assembling (well regarded by the high end audio equipment rebuilders).  Reseating connectors multiple times sometimes helps, but it doesn't always last.

 

Guess there's a chance it's your gauge meter itself.  You could create a faux temp sensor pretty easily with a resistor of the appropriate value and confirm operation right at the instrument cluster- eliminate ALL of the car's wiring in one swell foop.

[floatinghead]

Thanks for the responses.  Paul, it sits at the bottom and doesn't move.  

 

Does anyone know what the resistance value range the temp gauge needs to read correctly?  or at least begin showing movement o the gauge?  mine when warmed up was around the 210 ohms ( i believe).  

 

If it is the gauge, are they available new

or do i need to find one off the classified or other usual location?

 

 

Edited August 20, 2020 by floatinghead

[AustrianVespaGuy]

41 minutes ago, floatinghead said:

Does anyone know what the resistance value range the temp gauge needs to read correctly?

I forget if this for my E30 or 2002 sensor (though they may be the same, and I'm sure either way they're pretty close to one another), but at any rate I have 2500 ohms = 20C and 335 ohms = 80C, so yeah 210 ohms should probably be somewhere between 90 and 100C.

[floatinghead]

ok, that sounds about right as i'm around 2250 ohms when cold.  So looks like the sender is doing its thing.  And the wire looks good, i'm guessing its the gauge.  

 

Does anyone repair these?  and do the fuel/temp gauge come as a unit or separate?  I don't really want an aftermarket, but could get one to at least keep me informed in the near term.

[PaulTWinterton]

2 hours ago, floatinghead said:

find one off the classified or other usual location?

I may be wrong but it seems your gauge is stuck or dead.  Easiest test is replace with another.

 

I keep a spare instrument cluster to scuttle parts from.  $100 should get you a whole unit.  Do a Wanted ad.  I know some people here have a whole shelf of used ones.?

[Schon '02]

Replacement gauges are available:

https://www.rogerstii.com/bmw-2002-water-temperature-gauge/
 

That being said, I would take a careful look at the gauge once you remove it from the instrument cluster. It’s fairly fragile, and the case is thin gauge steel. When inspecting mine, I found two problems: The first was the mounting stud had pulled away from the back of the casing. The stud was used as a non-factory secondary ground point for the gauge. Over Tightening the nut on the back side of the circuit board had pulled stud from the casing. The second problem was a loose ground connector in 

he gauge itself. Correctly pushing this connector back onto the terminal spade fixed my gauge issues (needle pegged out due to poor ground).

[AustrianVespaGuy]

Put up a want ad or poke around on the classifieds; I'll bet within a week you can find someone on here that'll send you one for $50 or something.

[dlacey]

Short the wire at the sender to earth, gauge should read full scale.

[Mike Self]

Not sure if I've ever heard of the temp gauge itself failing--it's a pretty rare occurrence, which means that (1) there should be plenty of used ones around (2) used ones are most likely OK and (3) the problem is in other than the actual gauge itself. 

 

Schon 02's comments are well worth reading/checking out before you replace the gauge; yours may have something wonky inside the gauge itself that may be easily reparable.  Worth a look since it has to come out anyway.

 

mike

[floatinghead]

19 hours ago, dlacey said:

Short the wire at the sender to earth, gauge should read full scale.

 i just tried this.  turned ignition key, nothing.  then gave the top of the cluster a few taps and it pegged all the way up. thanks for the tip.  

 

So must be a ground connection?  maybe it was a bit stuck and also not getting a good ground?  I will pull the sender and clean the threads then give it another go all connected.  

 

[conkitchen]

15 minutes ago, floatinghead said:

So must be a ground connection?  

 an easy quick way to diagnose grounds at the cluster is to take an alligator clip/wire and attach it to the threaded mounting posts. Then clip the other end to the chassis.  

 

but what do I know

[jimk]

55 minutes ago, floatinghead said:

So must be a ground connection? 

Most likely and it's usually the ground trace in the printed circuit board that forms the back of the cluster, not the cable ground ore else nothing else would work that needs power in the cluster.

[floatinghead]

14 minutes ago, jimk said:

Most likely and it's usually the ground trace in the printed circuit board that forms the back of the cluster, not the cable ground ore else nothing else would work that needs power in the cluster.

if this is the case, is it easier to just replace?

 

New info:  So with the wire at sender grounded, i can peg it into the red.  I undid that and plugged the wire to sender as normal, I ran the engine till warm and it will move about an 1/8". I only noticed it when i turned it off and it dropped all the way down. 

 

 

 

 

Edited August 21, 2020 by floatinghead