Temp gauge gone from working to working differently (Or not)

[Middle29]

Previously temp gauge seemed to work perfectly, came up to halfway where the red warning light is consistently.

I had some work done on a blowing manifold and also new oil return etc. In the process the belt for the coolant pump was reversed as it was previously fitted the wrong way around on my AAZ.

Since then temp gauge struggled to come up to temp. The red light flashes on start up and after driving the indicator moves from way off the scale on the right to just inside the white indicator. So it's moving but only a tiny amount. I get plenty of heat out of the vents. 

Fuel gauge works fine.

I'd appreciate some help on where to start looking first and if these set of conditions indicate something obvious. I have a meter.

Recently cleaned up contacts / grounds on batteries and alternator for a charging problem that still exists. 

[Mocki]

Unplug the gauge sender and bridge the connections in the plug, this should give you a FSD on the gauge and red flashing over temp light if the wiring is all good , which will point at the sender being faulty ….. if not its a wiring issue , more than likely due to the work carried out near by displacing and or damaging the wiring

[Middle29]

Thanks, appreciate the reply - Do you mean unplug the sender on the engine? And if so is this it in the pic circled yellow?. I think I read red and yellow wires but wires have browned a bit with age. Engine running or ignition on?

[lefty67]

Have you checked the wiring ro the coolant temp senders or the temp senders themselves.?

[Mocki]

I dont know where the sender is , you have a non standard engine , sorry

[Middle29]

No I haven't checked anything yet. I'm not sure of their locations. Obviously 2 wires coming out of coolant tank, I'm guessing that's for coolant level warning light? and I know there is a temp sender on the engine somewhere (as maybe marked in my pic). I've read in the wiki about removing and buffing/cleaning the plug that feeds the dash gauge.

Mocki's instructions sound simple - But I didn't quite get location of which part I am bridging but assuming it is the plug into the sender on engine. 

Maybe I need another post in alt engines asking for location 

Cheers

[ZsZ]

The sender in the coolant tank is the level sensor.
The temp sender is either the yellow circled one or it is in the back side flange where the heater hose connects

A standard JX wiring should have 3 coolant flange senders. Two standard temp senders (one for the glow plugs one for the gauge) and a temp switch for the aux pump.

The gauge sender should have a yellow wire with red stripe and a brown wire for ground on your late style senders.

[lefty67]

There are 2 coolant temp senders on my aaz. One is for temp gauge.
Look like this

https://brickwerks.co.uk/product/coolan ... ternative/

[Middle29]

I found the problem. The sender was the one I circled in the picture and on closer inspection a wire was hanging by a thread just inside the plug so it wasn't obvious at first... plus my eyes aren't as good as they were.

As ever thanks everyone for responses and helping to narrow it down. Will fix or replace.

[Middle29]

So fixed this, spliced wires, solder and heat shrink. Also redid an earlier repair to alternator pigtail from crimps to solder and heat shrink (Have another thread about alternator voltage). Started up and temp gauge moved slightly further but much the same really but battery light stayed on (I think this happened before but rarely), alternator voltage much improved.

After stopping and restarting the battery light went off, alternator voltage dropped somewhat but then I noticed rev counter wasn't working. So I drove a bit, pulled over and out of nowhere rev counter sprung into life.

Admittedly I haven't bridged sender wires as suggested, mainly as I thought I'd discovered the problem with the wires to sender being frayed/about to snap.

Is this sounding more like an electrical problem at the dash end?

[Aidan]

connector at dash maybe a bit loose/displaced or not fully supported, the tab the circuit board is wrapped around is often broken and the plug support piece often missing