Is EGT probe stuffed?

[Deevo]

This weekend I fitted boost and EGT gauges to the Troll. The 2 wires from the probe are wrapped in a woven stainless steel sheath and come coiled up in the box. Whilst feeding the the probe wires through the plumbing adjacent the clutch M/C, the coiled sheath unravelled and touched the positive battery terminal. The SS sheath had 2 scorch marks but I soldiered on. When I went for a 5 minute test drive, nothing happened on the gauge. I disconnected the 2 probe wires and found there was continuity between them so I assumed the inner 2 wires had fused together at the 2 scorch points. I snipped the sheath back and found the wires were discoloured but not melted. I then separated the pairs of wires and checked for continuity again - which it had. So .... should there be continuity between these 2 wires when the probe is cold or should it be open circuit? i've checked the other wiring against the instructions and that all seems OK. The gauge even lights up when the parkers are switched on. Any advice anyone?

[GeeYou8]

There should be only a few ohms on the probe, it is just 2 different types of wire welded together at the tip, the different metals produce a very small voltage proportional to the temperature difference between the probe & the gauge.
is it a digital or analogue gauge?
If it is analogue try reversing the probe wires.
Graham

[Deevo]

Graham.
The gauge is analogue and the wires can't be reversed as they're male and converse female bullet connectors. I've been back to Autobarm and they're prepared to let me swap components to see if they're faulty. The guy said they have very little trouble with Saas gauges ..... I bet they say that to all the boys

[the evil twin]

What GU8 said ^^^^

Thermocouples are suprisingly robust and having continuity is a good sign.
Check from each wire to shield, that should be very high.
If that all checks out and it still doesn't read the EGT, swap the wires around.

[Deevo]

Thanks Evil Twin. Please see reply to Graham. When you say 'Check from each wire to shield, that should be very high' do you mean high resistance or high continuity?

[GeeYou8]

Deevo
High resistance, should be open circuit.
BTW Devo was my nickname when I worked in Melbourne for Ansett.
Graham

[Deevo]

Thanks Graham. Ansett hey. That must have been a long time ago! I suppose not too many on this forum would know what Ansett was. We're both giving our age away
And as for my nickname of Deevo, well that's a very old stone best left unturned.

[Deevo]

Well here's the latest guys. I took the car down to Autobarn and we installed a new probe. No change! Next we fitted a new gauge. No change again. Then the sales guy had no option but to get under the dash and check out my connections. He agreed I'd wired all the right colours to the right sources. He had no more ideas, so gave up. The only thing we didn't replace was the short cable that runs down the A pillar from the gauge to near the accelerator pedal. I decided to wriggle the wires while the engine was running and suddenly the gauge read. I thought it was a dodgy crimping into the bullet connector so I soldered it. This didn't fix anything but if I touched the bare connector with my finger the gauge read. If I touched it with anything metal or left it alone, it read nothing. What the hell is going on? I then did away with the M + F bullet connectors and soldered the wires directly to each other. Nothing! But the moment I touch it with my finger it reads. Any ideas would be great and a solution would be even better.

[threedogs]

Deevo
High resistance, should be open circuit.
BTW Devo was my nickname when I worked in Melbourne for Ansett.
Graham

What years were you at Ansett Melb, most of my mates were either
TAA or Ansett back in the day

[LostBenji]

Bloody frustrating as hell, ins't it?