Boost gauge not working always at 0

[Mike80911]

The boost gauge in my 89 is not working it stays at 0 all of the time I can definitely feel the boost coming on but the gauge always remains at0. Everything is factory, gauge IC etc. Can anyone point me in what direction to start with to try and resolve the issue?
Thanks

[Alan L]

Is that the gauge in the tach? Electronic?
If so, the sender unit may be stuck?
Alan

[Mike80911]

Yes it is in the tack, the original set up. Is the sending unit the large red covered one behind the IC?

[Alan L]

Yes. Not quite sure how to test it. never had an issue. About the only bit of the car I haven't had an issue with. But if there is a bad connection, the gauge pegs to max.
Somehow need to verify it is working.
Off the top of my head I would prob make up a fitting with a gauge on it and plug that thing in as well. While wired to the car. Then pressurise and get to say 14 psi and see if it is registering in the tach. You would need to clip an earth wire from the gauge to the car somewhere.
Someone else may have a better suggestion.
I have lots of fittings and plumbing type bits and a compressor and regulator - so that would be the easy track for me. Maybe not so for you.
Alan

[Mike80911]

I have been able to find threads where the gauge is pegged at max but not with it at 0. So trying to figure out what may be causing it not to read anything.

[Alan L]

I guess the first thing I would do is carefully pull the tach (comes straight out). Ease it out - don't want to go yanking the wires off. And check all is connected there.
Alan

[flightlead404]

Originally Posted by Mike80911

Yes it is in the tack, the original set up. Is the sending unit the large red covered one behind the IC?

That's the one

also back there is the overboost pressure switch.

Its easy to get the two spade connectors swapped. One is white and one is brown but I can't remember which is which.

Or maybe the spade connector came off or something compromised the connection.

[Alan L]

White one is o/boost.
Alan

[Mike80911]

Update. Using another thread on the subject I took everything apart and checked continuity on the sending unit and it was in range. Then grounded it and the gauge pegged so figured gauge and sender were good. Then I reconnected everything paying attention to where the IC mounts to the coil bracket where I would imagine that is where it grounds. Put it all back together and gauge is working so I am figuring it had a bad ground. Thanks for all the advice. Now onto the next issue with a new thread for that coming soon.