Boost Gauge Stopped Working for No Reason

[zakthor]

Drove car today, 1979 930. Turbo is making power and turbo noises but stock gauge isnt registering. Was working 4 days ago.

Havent been under the car for a while so this happened spontaneously. What should i look for?

I suppose theres a hose from somewhere to somewhere. Its broke or disconnected but where?

Thanks!

[mark houghton]

Originally Posted by zakthor

Drove car today, 1979 930. Turbo is making power and turbo noises but stock gauge isnt registering. Was working 4 days ago.

Havent been under the car for a while so this happened spontaneously. What should i look for?

I suppose theres a hose from somewhere to somewhere. Its broke or disconnected but where?

Thanks!

Your boost gauge sending unit can be seen either mounted to the IC or to the intake manifold. Totally electric, no hoses involved. Not sure about '79 models, but my '87 is clearly visible as a 2" diameter thingy with an orange silicone rubber cover. Possibly it has failed or wires have poor connections.

[zakthor]

Originally Posted by mark houghton

Your boost gauge sending unit can be seen either mounted to the IC or to the intake manifold. Totally electric, no hoses involved. Not sure about '79 models, but my '87 is clearly visible as a 2" diameter thingy with an orange silicone rubber cover. Possibly it has failed or wires have poor connections.

Clearly visible?

With flashlight i think i see a glimpse of its upper edge behind the fan, under the intercooler. Its screwed into the side of the giant air meter thingy?

Is visible in the first pic in this thread with intercooler removed:

https://forums.pelicanparts.com/porsche-911-technical-forum/269903-84-930-turbo-relay-question.html

Def need to take intercooler out to see it on mine. Ok wish me luck!

[zakthor]

Wire at sender intact. 1 wire, right?

How can i test it? Hook to bike pump and measure resistance?

[zakthor]

Ok, gorilla tape to bike pump. Default resistance is 6.8 ohms, resistance smoothly rose to 16 or so before that tape failed. I wont try to see if its caliberated but sender is sendering.

Im going to check back of tach, maybe wire on that side came loose. And once exposed i can check it for continuity.

[zakthor]

Whelp. Tach had no hanging wires.



Tail between legs i buttoned it all up and now the sender works.

Car just wanted that sort of attention.

I did notice the diaphram on sender is a bit loose. Maybe i should have put some solder in that joint for ground. Or maybe it needed a bike pump pressure test to crack it loose inside.

Something tells me ill be visiting this again.

Cheers.

[mark houghton]

Glad it's working now. Quite often it's just a poor ground, and the act of removing and screwing it back in does the magic.
Years ago I posted something diagnostic on the topic....found it. Your resistance readings seem ok.

https://forums.pelicanparts.com/911-930-turbo-super-charging-forum/531263-p-930-78-electrical-problem-boostgau.html?highlight=Sending+unit+ohms