Author Topic: Switching to gauges. Need help!!!!  (Read 11657 times)

Online bd

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Re: Switching to gauges. Need help!!!!
« Reply #15 on: August 05, 2012, 08:31:04 PM »
I think I figured it out. I traced the wire to the junction block on the fire wall and then to the gauge from the fire wall. I could see where it was getting power so I unscrewed the junction block at the fire wall to find that underneath it was covered with something stick and nasty. Guess some how it was cause electricity to flow across. Hopefully this fixes it.

You're certainly on the right track.  But, (if I understand what you just posted) that black, sticky 'goo' may be an anti-oxidant paste injected into the bulkhead connector at the factory.  It is intended to seal and protect the electrical connections from weather.  Can you post a pic of what you're seeing?

...Where would that wire be receiving power from?  I can follow it to the fire wall.  It's the exact same color wire plugged into the harness.

Study the wiring diagram linked below...
http://www.73-87chevytrucks.com/techinfo/wiring_diagrams/77-80_SBC_eng.jpg

Look along the right side of the wiring schematic, about the center of the page, directly below the wiper motor.  You'll see an illustration of one-half of the firewall bulkhead connector as it appears in the engine compartment.  Find ckt #31 and follow the wire to the sender (.5 TAN - 31(SXL)).  Note which cavity of the bulkhead plug the wire comes from.  Now, look under the dash at the opposite side of that connector.  Is that the wire that connects to the oil gauge?

NO - you have the wrong tan wire connected to the gauge.
YES - you need to continue physically tracing the tan wire to determine where it is picking up power.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline bgarr01

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Switching to gauges. Need help!!!!
« Reply #16 on: August 06, 2012, 09:26:00 AM »
Alright. Got the oil pressure gauge working along with the volt gauge.

The only issue now is that the temp gauge sits on hot. I changed out the temp switch on the heads. What would cause this?  It starts in the cold position but goes to hot within like 15 seconds.

Offline bgarr01

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Switching to gauges. Need help!!!!
« Reply #17 on: August 06, 2012, 09:27:46 AM »
I also just noticed that when you turn the key on it flips back to cold, however without the truck started it continues to raise.

Offline bgarr01

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Switching to gauges. Need help!!!!
« Reply #18 on: August 06, 2012, 10:13:19 AM »
I found the plug at the junction block according to the diagram above ckt #35 and followed it to the temp switch. The diagram shows only 1 wire I have 2. 1 connected to the temp switch the other dangling freely. I tried to connect it as well and same thing happens. Tried connecting just it and same thing happened.

Online bd

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Re: Switching to gauges. Need help!!!!
« Reply #19 on: August 06, 2012, 11:14:45 PM »
Step 1 - Disconnect the green wire from the temp sender and unplug the harness connector from the back of the instrument cluster.  Use your ohmmeter to check continuity on the green wire [ckt 35] between the gauge and the sender.  This will ensure you are working with the correct wire all the way from the gauge to the sender.  There should be zero resistance (0 ohms).  Next, with the green wire still disconnected at both ends, check continuity between the green wire and a verified good ground - it should register as an open circuit with infinite resistance.  Finally, turn the key ON and use your voltmeter to measure between the green wire and ground - it should register zero volts.  If this checks out okay, go to Step 2.  If it doesn't check out, figure out:  (A) where you went wrong, (B) where the wire is touching ground, or (C) where the wire is picking up power, respectively.

Step 2 - Carefully service the connections between the temp gauge and the PCB...
All of the gauges in the instrument cluster connect to the flexible printed circuit board (PCB) on the back of the cluster housing, via shiny silver colored metal clips.  Commonly, dust and tarnish degrade the connections between the gauge prongs, the clips, and the PCB.  Use a rubber eraser to burnish the PCB foil (be careful, because the foil peels free from the board easily).  Use crocus cloth to burnish the clips.  You may need to increase tension on the clips for a good connection to the PCB and the gauge prongs.
Pay particular attention to the ground circuit!  If this checks out and the temp gauge still acts up, I think you'll probably need to replace the temp gauge.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)