Author Topic: oil pressure and temp gauge stopped working  (Read 584 times)

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Offline rickspiller

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oil pressure and temp gauge stopped working
« on: October 26, 2018, 08:54:49 PM »
was trying to replace some of the lamps (reaching from behind dash), noticed that the printed circuit
was brittle, cracked - very bad shape. Now the oil pressure and temp do not work (they did work before I dicked around
behind..).
Is it safe to say its the printed circuit??
 
Does anyone know a  vendor that has the PC for a 75 TA with gauges and tach?
I was also thinking of sending out for a refurb, any thoughts on that?
thanks

Offline b_hill_86

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Re: oil pressure and temp gauge stopped working
« Reply #1 on: October 26, 2018, 11:30:59 PM »
Lots of places to get the circuit. Google “firebird printed circuit” and several will pop up from various sites.

I can’t say for sure it’s the circuit but sounds like a good shot if it was brittle and cracked in at least onc location. Really, it’s not hard to pull the cluster and inspect the circuit. I’d think you’d be able to see if a particular circuit was open (broken)
« Last Edit: October 27, 2018, 05:41:12 AM by b_hill_86 »
-Brian-

1977 Trans Am 400 4 speed hardtop

Offline b_hill_86

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Re: oil pressure and temp gauge stopped working
« Reply #2 on: October 26, 2018, 11:40:30 PM »
Was just looking at a picture of my circuit and remembered that gauge shares a ground with some of the dash lights I think so it’s possible when replacing some bulbs the ground circuit could have been damaged. Just a guess since both oil and temp quit working. Each would have their own “feed” from their respective sensors so a failed common ground could cause the whole gauge to quit at once. Do all of your cluster dash lights work now? Turn signals, etc?
-Brian-

1977 Trans Am 400 4 speed hardtop

Offline rickspiller

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Re: oil pressure and temp gauge stopped working
« Reply #3 on: October 27, 2018, 01:16:12 AM »
looking at the schematic, both senders are to ground, so I'll bet that both gauges lost 12v IGN.
Got a similar reply to look at this.
Temp gauge has two terminals(#2 sender and #1 IGN)
Oil Pressure has 3 (#1 sender,#2 IGN and #3?)
anyone know what the third is ?
I attached a screen shot.

Offline b_hill_86

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Re: oil pressure and temp gauge stopped working
« Reply #4 on: October 27, 2018, 05:59:50 AM »
#3 you have marked is a ground. I assume maybe common between the two? Trace the circuit. You’ll see it’s shared with a few lights nearby and goes to that top right pin where the connector goes. Loss of ignition would make sense too. I just thought since you were messing with bulbs and some bulbs share a ground with the oil and temp gauge that was a likely place to start.
-Brian-

1977 Trans Am 400 4 speed hardtop

Offline rickspiller

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Re: oil pressure and temp gauge stopped working
« Reply #5 on: October 27, 2018, 04:47:03 PM »
Got all the connections mapped out now. Gonna try to wiggle it out partially
and make some measurements if I can. if not, will drop the steering column and take it out.
thanks again Brian.

Offline b_hill_86

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Re: oil pressure and temp gauge stopped working
« Reply #6 on: October 27, 2018, 10:19:22 PM »
No problem. For what it’s worth, you only need to drop the column less than an inch or so to slide the cluster out. Don’t forget your tac plug, obviously the big connector and the speedo cable and you’re in business.
-Brian-

1977 Trans Am 400 4 speed hardtop

Offline b_hill_86

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Re: oil pressure and temp gauge stopped working
« Reply #7 on: October 27, 2018, 10:23:28 PM »
O and the fiber optic wire from the ashtray to the cluster. It is upper right as you sit in your seat looking at the cluster as normal and reach up behind
-Brian-

1977 Trans Am 400 4 speed hardtop