fuel and temperature gauges fail with headlights on

[937carrera]

OK, so my hunch is that the voltage regulator isn't working correctly (because two instruments have problems and the voltage reg is common), it could be a poor connection from the legs onto the ribbon , or it could be just failing.

Have a read here http://archive.club8090.co.uk/viewtopic ... 39&t=55012 on how to test the dashboard voltage regulator - it should give out 10v

and here for some photos and source for a replacement if needed

https://www.brickwerks.co.uk/voltage-re ... panel.html

Instructions are in the first linked thread - meter on DC volts, there's probably a ~20V setting unless auto adjusting.

[Luftmensch]

Thanks for recommending a source for the voltage regulator but I don't think I'll be needing it. I had a look at the older post you referred to and followed up on some of the advice and I think the problem might be solved now but I'll have to get back to you a little later, perhaps this weekend, to say for sure because I'm with my youngest son all day today.

[trundletruc]

The temperature gauge is earthed at the back of the van in the engine compartment. I would clean this up - it is a bolt just below the coil on the left side of the engine and has a number of brown wires going to it. It is often difficult to remove as the other end of the bolt is in the wheel arch and gets all the muck and dirt.
The fuel gauge earth is in the most stupid place between the floor of the van and the petrol tank! This is on the left side and you might be able to see it through the left wheel arch. You might be able to cut the wire and extend it and earth it somewhere where you can get at it.
This might be two problems? I would try cleaning the temperature gauge earth first and see what happens.

[trundletruc]

Ohps! Forget what I have just written!
You have a 1983 van and will have the early cooling system and with that system the temperature gauge sensor earths through the attachment to the steel tube that runs across the top of the engine and does not have an earth wire. It uses the engine earth. Sorry!

[kevtherev]

Ohps! Forget what I have just written!
You have a 1983 van and will have the early cooling system and with that system the temperature gauge sensor earths through the attachment to the steel tube that runs across the top of the engine and does not have an earth wire. It uses the engine earth. Sorry!

So is your engine well earthed?

[MidLifeCrisis]

***********B*gger - missed an entire page of replies so my comments below seem a little late to the game now!! Oh well - I’ll leave them up in case they are useful ************


If both the fuel and temp are failing at the same time then it is probably the voltage regulator that supplies a steady 10v to those circuits;
So the failure is probably either the voltage regulator itself, the power going to it, or the ground connection going to it;
Next time the gauges fail, check

1) Does the turn signal indicator light still work on the dash - if not then it’s the 12v power into the dash that is failing
2) Does the high beam blue light work - if not then it’s probably the ground signal into the dash that is faulty (this is still the most likely/common problem)
3) If both the above still work (while the gauges do not) then the fault maybe the regulator which is a little device screwed to the back of the dash and quite easy to replace/check

Let us know how you get on with diagnosis?

In case it helps - below is a (simplified) version of the wiring in the dash incase it is useful (this is early dash wiring with temp gauge but no rev counter or clock etc)

[Luftmensch]

Here's a brief update:
Started the van just now after having connected all the instrument panel wiring and switches and ensuring good connection with the dash volt regulator. Fuel gauge was working but the temp gauge did not move. Then after running the engine for about 4 or 5 minutes the fuel gauge stopped working. I think this might have happened when I switched on the high beams while testing the instruments (switching on off various dash appliances). The fuel gauge briefly woke up again a few minutes later but then quickly stopped functioning again. I kept the engine running for another 5 to 7 minutes without either gauge coming back to life.

* New symptom ... flashing red led light above brake light warning indicator. Light continues to flash even after the engine is shut off. I would think it must be unrelated to the gauge problem.

Thanks to midlifecrisis for the wiring diagram. will look at it in further detail later.

I have not yet investigated the ideas in kevtherev and trundletruc's comments.

in response to midlifecrisis ' questions : green signal indicator lights on inst panel still work and high beam blue light works.

One lingering question .... if it's the voltage regulator, why do the symptoms occur when I have the headlights on? if it's was the voltage regulator wouldn't the gauges fail all the time, even with the lights off?

[MidLifeCrisis]

One lingering question .... if it's the voltage regulator, why do the symptoms occur when I have the headlights on? if it's was the voltage regulator wouldn't the gauges fail all the time, even with the lights off?

This does sound a lot like a bad ground issue;
Headlights on would stuff a voltage into the dash illumination lights which then try to ground through the dash ground - if that ground is rubbish then it could raise the voltage at the dash ground (and the regulator ground) and mess with the voltage regulators ability to give the nice 10v that the gauges need;
You could try temporarily grounding the voltage regulator tab with a bit of wire to the metalwork to see if that ‘cures’ the problem

[Luftmensch]

Sorry everyone, I had no time to get to the volt regulator until yesterday. I've replaced it with the modern version sold by brickworks.co.uk. After a brief test, it now seems as if the fuel gauge works (even with headlights on) while the temp gauge fails all the time (with or without headlights on). This was with running the van for about 7 or 8 minutes, enough time to where the temp gauge should have been registering.
I’m a bit confused about the terminals on the volt reg. and whether the metal screw-down anchor point in the device functions as an earth terminal. The replacement version that I installed has no metal contact for the screw-down anchor point, it’s a plastic to metal junction (where it meets the printed circuitboard). I’ve included a few images of the voltage regulator so that someone might be able to help me understand how it works. The top two images are from the Brickwerks website showing the old type regulator and their modern replacement version (with no metal contact to the printed circuitboard). The bottom left image is a closeup of the wiring diagram sent by midlifecrisis, and the image on the right is from the haynes manual. The image of the wiring diagram sent by midlifecrisis actually shows the voltage regulator set-up my van, where the middle straight terminal is left unplugged. According to the Haynes manual though this should be the earth terminal, so I’m wondering which one is the correct configuration.

[937carrera]

Look at the guidance on the Brickwerks site - IIRC the legs are reversed from OE part

[Luftmensch]

Yes, I did head the instructions on their website.
Any thoughts about the varying arrangements in the composite image I attached in my last message?

[937carrera]

Not from me - best wait for someone who has actually done the job

[MidLifeCrisis]

Yes, I did head the instructions on their website.
Any thoughts about the varying arrangements in the composite image I attached in my last message?

I’m guessing that you have something like the below - in which the pins are (from left to right when viewed with the flat side of the component downwards - as in the pic below )

1) Voltage In (Battery = 12v)
2) Ground
3) V Out (10v)



As Brickwerks state it is mounted upside down (so flat side up) because the original components had the legs the other way around)
Also in the original the mounting tab (which the screw goes through) was also a ground connection. - which is probably not true of the new component that you have;

So either you need the middle leg to be inserted into its electrical connection (if one exists) or you need to somehow attach the middle leg to the mounting screw so that there is a good ground connection.

Does that make sense?

[Luftmensch]

Yes, that's the type I installed. Thanks for clarifying the function of the terminals.
On my van there is no socket to accept the middle (earth) terminal so (as you said) I'll need to find a way to attach it to the screw. But now that the screw only make contact with the plastic housing of the new voltage regulator I'll also need to somehow bridge the screw to the circuit board (perhaps with a thin flat strip of copper), isn't that right?
also, I wonder if I can bend the middle terminal on the volt reg. backwards far enough that it could make contact with the screw?

[AngeloEvs]

The centre nut of the temperature guage connects to earth, I would use a light gauge insulated wire with a small eyelet tag on each end and fix one tag under the centre nut of the gauge and the other under the screw or bolt securing the regulator tab (which is the Regulators 0v connection), your regulator will now be grounded.

PM me your address and I will send you a lead with tags ready to fit.