Speedometer, fuel gauge, temp gauge not working

[FarWare12]

Hi. I recently bought a T25 and the speedometer, odometer, fuel gauge and temp gauge are not working. The warning lights do work.

Could this be one simple electrical problem? I read in other threads that it could be a faulty voltage regulator, but the previous owner told me he thinks the speedometer cable needs to be replaced. However, I wonder if the problems on the dashboard are all related. Where and how should I go about checking this?

Also, apparently, the radiator fan doesn't work. Could this be related to the temp gauge not working?

[Aidan]

Many electrical issues are due to bad earths, and many bad earths are due to leaking windscreen and or condensation affecting the earthing points

Speedo is mechanical

Radiator fan is controlled by its own circuit with the sensor that switches being in the radiator

Download the manuals from Syncrosport or Sir Adventure websites, these vans are pretty simple, you just need to be methodical but with a sub £10 multimeter and common sense and some patience you can usually fix most things or at least narrow down the issues to the point where it is easier to pinpoint

The dash is prone to plastic degradation and basically falling apart but it relatively easy to fix if you are at all practical, often the problems are due to cack handed bodgers who have been before you

[FarWare12]

I tried replacing the 10V TCA700Y voltage regulator on the back of the dash with a L78S10CV one, but that didn't work.

Any suggestions for where I should look next? How do I know the blue foil is not simply degraded?

[lefty67]

As Aidan says I'd start by cleaning all the earth's.
Cheap and simple things first

[mioba]

Drop fuse box,
locate earth crowns, have fun
I went through my entire wiring last year. Old copper and degrading crimps you will find with connections breaking in your hands.

Aidens post above is spot on.

Speedo is a worm cable - mechanical.

My money is on worn copper tracks on the blue pcb where it folds into the connection block.

Some silver conductive paint. Masking the tracks and a steady hand.

[dcworm57]

I was having issues with oil temp and battery lights flashing . 
I replaced the voltage regulator on the alternator and that sorted the problem . Very easy to change . You tube videos 

[FarWare12]

Today I thought I'd have another crack at these issues. I gave up last year after replacing the voltage regulator didn't work but I've been having nightmares about running out of fuel while driving so I thought I'd give it another go.

The speedometer was fixed last year by my mechanic. Apparently he cleaned up the cable a bit and it started working again although it vibrates a bit. The fuel and temp gauges are still not working.

Today I checked the regulator again with a multimeter and it still gives me the correct output (12V in, 10V out). I then checked pin 7 (lilac-black, fuel gauge) and pin 6 (yellow-red, temp gauge) on the 14 pin connector behind the panel. Pin 6 gives me 10V but pin 7 gives me 0V, so it seems nothing is coming from the sender. I also tried to measure the resistance of the earth points behind the fuse box. Some seemed quite high. I took those off and reconnected them. It was hard to reach them without removing the whole dashboard though. I could barely reconnect them and didn't think about cleaning them, because I simply couldn't reach them. After reconnecting them, they were showing about 1 Ohm or less. However, this doesn't seem to have helped my issues.

I heard though that the lilac-black cable is connected to a 4-pin connector behind the fuse box, is that right? I didn't notice that today, but I might have another look tomorrow.

[Aidan]

work the other way, what is the resistance of the fuel sender as seen at the 14 pin plug, with the plug disconnected and meter lead on pin and other lead on a good body earth ? If it is zero (ie continuity to earth) then there's a wiring fault between fuel tank sender and the dash, but the gauge should when connected show fuller than full (it's an inverse resistance reading) - if you've half a tank you should have a few 100ohms resistance, if it's infinity or mega ohms then there is also a wiring issue with excess resistance somewhere

You need the wiring diagrams available from Syncrosport or Sir Adventure websites to understand how the wiring is done, and ideally the Bentley manual for the logical step by step test procedures, which is available via a post in Members only, which is also useful if having a mechanic or auto electrician work on the van so they can see how it is wired and how it is supposed to work

[FarWare12]

work the other way, what is the resistance of the fuel sender as seen at the 14 pin plug, with the plug disconnected and meter lead on pin and other lead on a good body earth ? If it is zero (ie continuity to earth) then there's a wiring fault between fuel tank sender and the dash, but the gauge should when connected show fuller than full (it's an inverse resistance reading) - if you've half a tank you should have a few 100ohms resistance, if it's infinity or mega ohms then there is also a wiring issue with excess resistance somewhere

You need the wiring diagrams available from Syncrosport or Sir Adventure websites to understand how the wiring is done, and ideally the Bentley manual for the logical step by step test procedures, which is available via a post in Members only, which is also useful if having a mechanic or auto electrician work on the van so they can see how it is wired and how it is supposed to work

Alright, good idea, I didn't think about measuring the resistance. So if the resistance changes, does the voltage always remain the same? I know quite little about electricity. I've been trying to figure out most things with ChapGPT today. ChatGPT tells me that the voltage regulator sends 10V to the fuel sender, but the sender can decrease the voltage based on the content on the tank. But when I asked it about the resistance just now, it also suggested me that this can give me an indication if the fuel sensor is working or not.

Thanks, will try this tomorrow
 

[FarWare12]

work the other way, what is the resistance of the fuel sender as seen at the 14 pin plug, with the plug disconnected and meter lead on pin and other lead on a good body earth ? If it is zero (ie continuity to earth) then there's a wiring fault between fuel tank sender and the dash, but the gauge should when connected show fuller than full (it's an inverse resistance reading) - if you've half a tank you should have a few 100ohms resistance, if it's infinity or mega ohms then there is also a wiring issue with excess resistance somewhere

You need the wiring diagrams available from Syncrosport or Sir Adventure websites to understand how the wiring is done, and ideally the Bentley manual for the logical step by step test procedures, which is available via a post in Members only, which is also useful if having a mechanic or auto electrician work on the van so they can see how it is wired and how it is supposed to work

Aidan, does the temperature sensor work in the same way?

I just opened up the instrument cluster and tried to measure the voltage on the screws on the blue foil, in particular the three screws on top for the temperature gauge and the two screws at the bottom for the fuel gauge. I noticed that there was no voltage on the screw for the fuel gauge coming from the voltage regulator and that the nut on it was every so slightly loose. After tightening it manually, the fuel gauge immediately started working!

However, the temperature gauge still doesn't seem to work. At least, ... I didn't drive the car yet but I started it and I am assuming that the needle will come up at least a bit when starting the car won't it? I made sure the other screws were tight. The voltage on both screws is normal, 10V. I tried to measure the resistance between the earth screw, the middle of the three on top, and another earth and it was close to zero. I also unplugged the 14 pin connector and tried to measure the resistance on the yellow-red temperature wire to the earth. The multimeter didn't indicate anything (kept indicating 1, which is the standard value). From the fuel gauge wire I did get a reading, 38 Ohms. Tank almost completely full.

[Robsey]

The temperature gauge will not register until the coolant has warmed up a fair bit.
I suspect at least 50°C or closer to 70°C.
So from cold (currently 20 to 26°C) it will not move for at least five minutes of running.