Gauges temp and fuel reading high

Hi

I'm new to the forum and have bought a '94 300 tdi.
I've got the mod bug and have started tinkering. I've replaced all the rods and ends and started on the instrument gauge bulbs as they were poor in the dark so decided on some led's. Thing is they didn't fit all the way in so I had to remove the green bulb holder dome. Thing is I think (from checking on the net) that this held a earth ground wire in place as the gauges are now showing high.

Is there any way of opening the gauge up to solder this wire.

Thanks in advance

D2 OSK said:

Hi

I'm new to the forum and have bought a '94 300 tdi.
I've got the mod bug and have started tinkering. I've replaced all the rods and ends and started on the instrument gauge bulbs as they were poor in the dark so decided on some led's. Thing is they didn't fit all the way in so I had to remove the green bulb holder dome. Thing is I think (from checking on the net) that this held a earth ground wire in place as the gauges are now showing high.

Is there any way of opening the gauge up to solder this wire.

Thanks in advance

Click to expand...

bulb holder shouldnt effect guages earthing on gauges is for the gauge illumination, they are earthed through the senders, if you were to short wire from guage to sender to earth gauge would read highest, reduce the earthing and read lower

Right so that's eliminated the bulb holder theory, I'll check the wiring and u clamps again. I understand the earth on the gauges is supposed to daisy chain across gauges? Is there a earth for the speedo?

for the light holder, it doesnt have to be a daisy chain, though thats the simplest

Thanks for the quick reply JamesMartin

Will have another crack at it.

Right still no joy, I swapped the fuel gauge for a spare one that I had lying around and that worked fine so that would tell me that the problem is with the gauges. Now the only thing I did to the gauges was remove the green screw type bulb holder by breaking it from inside and pulling out. Back to square one. Any thoughts chaps.

I had the same issue on my 300 tdi,
Eventually fitted a nice set of VDO gauges, Volt meter in place of the clock, Temp (with the right sensor) much better than standard.
Fuel gauge worked perfectly, although backwards! Fill up at the pump, gauge reads empty, keep driving, and back to the pump when gauge reads 3/4 full!
Never did get to the bottom of the fuel gauge, sold it now, for a Td5
I was certain that breaking out the green bulb holder did something to the gauges, as mine were working fine before I did the bulbs.

I agree Luigi, I'm surprised that it's not been picked up more in the forums and by the suppliers of the bulbs, in fact the seller I got mine from said take the holders out. I would change to the upgraded gauges but I want to keep a balance between original equipment and subtle mods.

I suspect the LEDs are allowing more voltage to leak to the local earth, affecting the gauges. Try whacking a big earth directly from the battery to one of the gauges and see if the reading changes.

I thought that but I eliminated that by removing the LED holder from the gauge.

Easiest way to break the fault down is to run a new earth to the gauge, if that doesn't make any difference, then run a temp flying lead from the sender. If that doesn't make any difference, logically you have bu**ered the gauge.

zeaphod said:

Easiest way to break the fault down is to run a new earth to the gauge, if that doesn't make any difference, then run a temp flying lead from the sender. If that doesn't make any difference, logically you have bu**ered the gauge.

Click to expand...

a wire from the gauge metal body/earth to a big nut behind the dash will do. or if you have a multimeter...

Thanks for all the advice, I will have to have a crack tomorrow now, otherwise the better half is gonna have a real go at me. This defender lark is very addictive but also very frustrating. I have some sparco r333 seats waiting to be fitted but don't want to start that till the gauges are out of the way.

I have exactly the same issue...removed the green domes yesterday so that some light actually gets through... (but just cable ties to hold original bulb over hole = £0 ). Fuel, temp and volt all on max

I'm wondering if there is a metal O ring that has stayed in the gauge and is doing something with the current and confusing all gauges..??.. Contemplating taking the gauges apart to check all is well

ThreeTwo - I've got this problem and it's driving me mad, I have read on a different forum that there is some sort of thin wire connected to the long screw bolt type thing which the earth and u clamp attach to which goes to the green bulb holder thing and is held in place by it when tight.

However looking at the gauges I don't where you would open it from and whether they can even be put back together once opened.

Just taken the fuel gauge apart and all appeared well...not the best plan of action as it doesn't go back together so well!! Gunna have to take it out again and have another go.

I tried each gauge individually and each still read max so that must rule out any problem with actual gauges. I'm thinking there is a problem further down the loom at the connector maybe?? Run out of time now so its something to chase next week now

Well I got some time today for another go and ended up taking the fuel gauge apart. As a result of originally taking the green light cap out I must have damaged the wiring inside as a copper connection was broke. I tried soldering it back but this was futile. Luckily I had a couple of spare gauges so ended up putting smaller led's in to them which didn't require the green cap to come out. End result - working gauges. So if anyone is thinking about breaking those caps out I would think twice as these gauges are very fragile inside.

mine came pre-bust (the green bulb housing covers)... thought I chucked some LEDs in and they work a treat, can read the speedo and everything now...