Temp, tank guage won't work...

[StefanLee]

So I seem to have an electrical issue with my temp and fuel guage. In fact, they haven't worked since I got the car, but now I have gotten around to fixing it.

Neither fuel nor temp hand works when the engine is running, but the temp hand does move about a little when I turn on the ignition, so there is electricity. When the engine starts, it goes completely dead.

I suspect some sort of grounding issue, but I don't know where to start. The electrics have been redone with new wires of all the colours of the rainbow so it is difficult to see which wire does what. So I won't be helped by advice such as "follow the black lead" etc.

Also, how much pressure should the oil guage show when the engine is running? My guage is at full (5) with light off, so it seems to be working fine. I´m just trying to make sure it isn´t somehow shorting out and showing too much. Car electrics is a headache!

Thank for any help

[jlthunder]

Yes, it does sound like you have some electrical problems.

5 oil pressure? If the gauge doesn't move when warmed up between idle and 2000 rpm, I would say you have an electrical problem. On a cold engine I read between 3 and 4 and once warmed up, it reads between 2 and 3. HTH.

Does the oil light glow dimly when the engine is warm and at idle? If so, then the wires on the sender are reversed. Simple fix, reverse the wires on the gauge or sender unit.

[StefanLee]

Thanks for the fast reply.

No in fact the oil pressure jumps to five when the engine is started and stays there. The light comes on with the ignition but turns off at the start. I can't recall if the light glows dimly, I think it stays off completely. The volt guage reads a steady 14 volts or thereabouts with the engine running, so it works.

[jlthunder]

Opels never came with volt gauges. They only came with AMP gauges. Sounds like the PO made some major revisions.

[StefanLee]

Ooops, I meant the Amp guage. It is showing positive amps.

The instruments are the originals.

[jlthunder]

As long as the AMP gauge slowly returns to 0 or just above, the charging circuit is working OK. If it stays positive past the first tick permanently, then there is an issue with the charging circuit.

[newman27]

My gages are in good working order and here is what happens on my car for comparison purposes:

Amp: show just below "0" with light briefly while engine warms up then, after a rev or two of the engine, the needle jumps into the positive range, the light goes out, and the needle works its way back down to just above "0" and stays there the rest of the way (unless the headlights are turned on of course).

Oil Pressure: same as "jlthunder" posted above. Note that at idle on a warm engine it sits right at "1". I have never seen a reading above "4" as far as I can recall.

Temp: Fully warmed up after lots of driving, my car sits at the "half" mark up to the "3/4" mark depending on whether or not the car is sitting at a light.

NOTE: my temp gage jumped around a bit for a while and even was in the red occasionally. I put some dielectric grease on the wire contact and that solved the problem. Since then, the gage has been pretty consistent. It just needed a better contact.

As far as the fuel gage, maybe a bad sender unit? There was one for sale on eBay recently - may still be there...

HTH

Matt

[StefanLee]

Ok...

I went out to the garage and fired the beast up again, paying close attention to the amp meter. And yes, oi goes past the first tick, then slowly returns past the tick and stays there. When I turned on the headlights, the needle approached the center a little more, indicating the increased amp usage.

I didn't have time to warm up the engine, the car is in a garage and I didn't want to poison myself carbon monoxide... Still the oil pressure hand went to five and stayed there for the short period of time I had the engine running.

[Dan-MI]

On the water temp, check the wire at the sending unit. Mine has some sort of weird coupling that doesn't look like what the service manual shows. The wire has a tendency to work itself loose. So my guage will be working well, then it drops to zero.

[namba209 (R.I.P.)]

Stefan, according to my DESTEC schematic, here's how the wires are supposed to be hooked up to the gauges. Power for both come from a single wire off a terminal block between the speedo and ammeter. There is a ground wire on the ammeter that could be touching the power lead to the temp/fuel gage, so they don't work, and the same ground wire could be playing havoc with the oil gauge, too. Of course, if the dreaded PO has messed around with the wiring behind the instrument panel..........

[StefanLee]

Thanks Ron, that's a solid tip I'll look into. The wiring has been redone by the PO but I think I should be able to deciper it with the info you provided.

Now I just have to get that single shear nut off holding up the steering column...



Stefan

[namba209 (R.I.P.)]

Thanks Ron, that's a solid tip I'll look into. The wiring has been redone by the PO but I think I should be able to deciper it with the info you provided.

Now I just have to get that single shear nut off holding up the steering column...



Stefan

How about the shear bolt, instead of a nut? There's been a few threads on the how to. I've never seen one on either of my two GTs, but others have had to deal with them. Maybe time for a little searching expedition. If there's any more info I can give you from my schematic, lemmee know.

[StefanLee]

I´m now digging behind the instrument panel, and what a JOY it is!!!

It seems the tank sender unit isn't hooked up to the guage, maybe that's why it isn´t working!

Still, I´m a bit puzzled by my oil pressure guage. Before I do something stupid with it, I'm wondering if any of you fine gents might have an idea why it is showing too much. If it grounds it shouldn't be working at all, but what might cause the opposite? faulty sender unit?

Any tips appreciated.

Stefan

[jlthunder]

faulty sender unit?

Any tips appreciated.

Stefan

That could do it or a broken wire. I forget if it reads max or min if the wire is disconnected from the sender unit. The unit is at the rear of the passenger side of the engine. If you have a mechanics mirror, you can see it easier. Search the site for a replacement if it is needed. They still make it.

[StefanLee]

Ok, I´ll check it. The "no-pressure" warning light works ok though, since it comes on with the ignition but the turns off when the motor runs, ie. when the oil pump produces pressure. So it should be reading a signal from the sender unit, if the signal is good is another story...

[jlthunder]

Check out this thread on the oil pressure sending unit. It shows you where it is located and where to order a new one if you want.

http://www.opelgt.com/forums/6a-engi...ding-unit.html

Hey, can you get me Saab parts cheap? Just kidding!

[markandson]

I believe the oil gauge will stay at zero if the wire is disconnected. If it is always staying pegged high you probably have a bad sender with a short inside. Take the wire off at the sender and see if it reads zero, if it does then the sender is more than likely toast.

[namba209 (R.I.P.)]

J. J. Wheatley came through again on his DESTEC schematic. Here's the ohm readings for the bars on the oil gauge:
1st bar 45
2nd bar 77
3rd bar 113
4th bar 145
5th bar 175
gauge pegged 250

HTH.