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Wedge TR7 fuel and temp. gauges not working

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Andrew Mace

Andrew Mace

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Yes, I said TR7! I'm resurrecting an early 1979 convertible that has been in storage for over 10 years. So far, I've had quite good success with the usual long-term storage-related problems, such as freeing off the clutch disc, cleaning up grounds on lights, etc., etc.

One problem I'm having, though, is getting the fuel and temperature gauges to work. Near as I can tell, there is power to the gauge cluster, as the clock, voltmeter and tachometer and other bits all seem to work. Also, near as I can tell from the wiring diagrams in the Bentley Manual, there is no voltage stabilizer in the gauge circuit, so I'm guessing that's not a problem!?

Any thoughts from you Wedge folks as to where I can start tracking the problem? TIA for any and all suggestions!
 
if i let my fhc sit for a long time the temp gauge won't work until the engine heat cycles a couple of times. i am surprised the clock works. is it accurate? or does it gain time like both of mine do.
 
Andy -

That PC "board" that the gauges and lights are attached to might be the culprit. I don't remember which plug is which, but your two gauges may be on the same plug, which may have worked loose.

Either that, or the connections at the gauges may have tarnished.

As for the clock, I ditched mine a while back, and popped in an oil pressure gauge. It keeps perfect time. :wink:
 
Rover SD1 oil pressure gauge is pretty much a direct fit and looks pretty original as well I believe.

Any update Andy?
 
You need to see if you have power at the senders. Both gauges send power to the senders which have variable grounding abilities based on engine temp and fuel level. The gauges read the amount of resistance in the sending wires based on there ability to ground. In most cases the point where the wire clips to the sender needs to be cleaned. A quick check on the temp gauge is to remove the wire from the sender and ground it directly to the block. If the gauge pegs, your good to that point. So calling them senders is a bit of a misnomer. They are more like voltage receivers or grounders. The fuel gauge sender is a little more difficult. There are three wires. One is just a ground wire. One goes to the fuel level potentiometer, and one is for the low fuel light. That wire grounds completely when the float drops all the way down thus completing the circuit and allowing power to flow thru the low fuel light bulb. There are no quick fixes on wedge electrics. Get a test light and follow the electrons to the point where they stop. When all else fails, it's a ground.
 
tdskip said:
Any update Andy?
Click to expand...
Nothing today. Still watching for responses, and there are several great suggestions so far; thanks!

Maybe tomorrow I'll get back to it...IF I get enough lawns mowed and other yard and house jobs done! (and I'm not even married; I'm actually forcing myself to do the chores first! :laugh: )
 
Andy -

I have a spare cluster and took a look just now. The two gauges each have three terminals. Two of them are on a shared circuit with the voltmeter. Looking at the back of the assembly, with the fuel gauge and voltmeter to your left, the lower right-hand terminal of the fuel gauge, the lower right-hand terminal of the temp gauge, and the left-hand terminal of the voltmeter are common. The top terminals of the fuel gauge and temp gauge are also common with the right-hand terminal of the voltmeter. The other terminals on the temp and fuel gauges go to the harness connectors - the temp gauge on the smaller one (third from the bottom) and the fuel gauge on the larger (second from the left).

All the gauges make contact via screw posts which connect to spring clips screwed to the copper contacts on the pc film. It may be a simple job of removing the gauges and cleaning up all the contact surfaces.

Oh, and if your instrument lights are working, then the common circuits are probably OK, as they are in series as well.

Hope this helps. Let us know.

Mickey
 
My pleasure!

(Though I think I'm a bit cross-eyed from following those circuit lines! :crazyeyes:)
 
"As for the clock...wowzer...those never work."

I think my 1980, "8", was built when all the workers were sober and happy.
The clock keeps perfect time, but I think it's time to clean/replace the speedo cable.
:cryin:
tom
 
Hey mickey, how about a pic of the back of that thing so I could put it in my memory bank. Never seen one as I have never pulled mine
 
Once again Wedge heads,START WITH THE FUSE BLOCK!!!No matter what it may look like the connections corrode over time and you get a voltage drop across the fuse/fuses.They may still work but you now have gremlins.If you cherry out your fuses first you can then move forward in the process of fault finding.But often a 7/8 is miraculously better with some contact spray and some fresh fuses.
MD(mad dog)
 
MDCanaday said:
Once again Wedge heads,START WITH THE FUSE BLOCK!!!No matter what it may look like the connections corrode over time and you get a voltage drop across the fuse/fuses.They may still work but you now have gremlins.If you cherry out your fuses first you can then move forward in the process of fault finding.But often a 7/8 is miraculously better with some contact spray and some fresh fuses.
MD(mad dog)
Click to expand...

Thanks, MD - from his post, it appeared that he had ruled that out.
 
DNK said:
Hey mickey, how about a pic of the back of that thing so I could put it in my memory bank. Never seen one as I have never pulled mine
Click to expand...

I'll try to get that later today.
 
Mickey Richaud said:
MDCanaday said:
Once again Wedge heads,START WITH THE FUSE BLOCK...
Click to expand...

Thanks, MD - from his post, it appeared that he had ruled that out.
Click to expand...
Right. One of the first things my son and I did "electrically" on the car was to thoroughly clean up the fuse box, during which time we also replaced a couple of iffy fuses and put a couple others back in the right spots!

I think it was actually about, oh, 1970, when I first discovered the merit and logic of looking first at the fuses and then the fuse contacts in tracking electrical problems on Triumphs!
 
DNK said:
Hey mickey, how about a pic of the back of that thing so I could put it in my memory bank. Never seen one as I have never pulled mine
Click to expand...

Here ya go, Don. Clock is upper left in this picture. All gauges and lights have been removed.

PICT0303.jpg


If you need more resolution, I can email you directly. Large file, though.

Mickey
 
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