Author Topic: Switching to gauges. Need help!!!!  (Read 12016 times)

Offline bgarr01

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Switching to gauges. Need help!!!!
« on: August 03, 2012, 07:02:16 PM »
I purchased a gauge cluster with the oil temp and volt gauge. I currently have the idiot lights. I've looked at the diagram 900 times and have pinned it like I'm thinking it shows. Can someone please just tell me what order. According to the tech sections wiring pics I should be using 13 of the 15 wires. But the diagram shows numerous other wires that I don't have. I'm so lost. I have already installed the oil pressure unit.

Offline bgarr01

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Switching to gauges. Need help!!!!
« Reply #1 on: August 04, 2012, 09:56:16 AM »
Ok got mostly everything working. Now the only problems I'm having are that none of the new smaller gauges appear to be reading correctly. The volt gauge never moves. Just sets at 0. The temp gauge never moves and the oil pressure gauge is pegged out. I replaced the old sending unit for one with gauges. Any help would be appreciated.

Offline bgarr01

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Switching to gauges. Need help!!!!
« Reply #2 on: August 04, 2012, 10:16:29 AM »
Ya know just realized I didn't post the year or anything. It's a 79 Chevy 1/2 ton. The new cluster with the gauges is suppose to be out of a 79 as well. I used these 2 images to do the wiring. Just to clarify one of them is labeled common to above?  Can some one clarify this as well?

Offline slammed79

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Re: Switching to gauges. Need help!!!!
« Reply #3 on: August 04, 2012, 12:19:36 PM »
That looks about right. Verify that your printed curcuit board on the back doesn't have any burned curcuits, and check your grounds.
74 C10 Long bed 350/SM465 Lowered on 20's

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Online bd

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Re: Switching to gauges. Need help!!!!
« Reply #4 on: August 04, 2012, 01:09:47 PM »
General info:
* circuit numbers are in brackets [ckt #] to tie to the schematic diagram
* according to the schematic, your image is mislabeled (see position 9, below)
* image label: "Common for above" is 12-volt ignition (see position 16 for details)
* you should have three 12-volt ignition sources to the cluster (pink wires with a single black stripe) [ckt 39] in connector positions 4, 6 & 16
* you should have three ground wires to the cluster (black wires) [ckt 150] in connector positions 3, 8 & 10

Connector specific wiring:
* position 1 is high-beam dash indicator (light green) [ckt 11]
* position 2 is instrument lights (gray) [ckt 8]
* position 3 is ground for the volt gauge (blk) [ckt 150]
* position 4 is 12-v ignition to the volt gauge (pnk/blk) [ckt 39]
* position 5 is oil gauge sender (tan) [ckt 31]
* position 6 is 12-v ignition to oil pressure & temp gauges (pnk/blk) [ckt 39]
* position 7 is just a jumper wire connecting to position 18, fuel gauge sender (pnk) [ckt 30] - used only on models equipped with factory tach
* position 8 is ground for fuel gauge on models equipped with factory tach (blk) [ckt 150]
* position 9 is coolant temp sender (dark green) [ckt 35] - image is mislabeled as "fuel ground"
* position 10 is ground for fuel gauge, turn indicators, and instrument lights (blk) [ckt 150]
* position 11 is left turn dash indicator (light blue) [ckt 14]
* position 12 is right turn dash indicator (dark blue) [ckt 15]
* position 13 is seat belt warning dash indicator (yellow) [ckt 237]
* position 14 is not used on 2wd trucks
* position 15 is choke malfunction dash indicator (dark blue) [ckt 931]
* position 16 is 12-v ign for fuel gauge, brake warning & other dash indicators (pnk/blk) [ckt 39]
* position 17 is park brake & brake warning dash indicator (tan/white) [ckt 33]
* position 18 is fuel gauge sender (pink) [ckt 30]

Ok got mostly everything working. Now the only problems I'm having are that none of the new smaller gauges appear to be reading correctly. The volt gauge never moves. Just sets at 0. The temp gauge never moves and the oil pressure gauge is pegged out. I replaced the old sending unit for one with gauges. Any help would be appreciated.

Verify the wiring to the cluster then, as slammed79 suggested, check your ignition fuse and check the ground connection to dash sheetmetal.  On the oil gauge, you have an open in the sender lead.  On the temp gauge, ground the sender wire - if the gauge moves toward hot, you have a sender installed for a light.
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 #5 on: August 04, 2012, 02:33:51 PM »
Ok figured out the temp gauge. I have the sender for a light. Guy at auto zone told me there wasn't a difference. The volt meter still doesn't move. I thought I saw somewhere that I needed resistor? Now on to the oil light. How do I check for an open? In the wire?  It's reading 12 volts at the gauge and the sending unit. I appreciate all the help. Y'all make things so much easier.

Offline bgarr01

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Switching to gauges. Need help!!!!
« Reply #6 on: August 04, 2012, 02:48:15 PM »
Alrighty. The volt gauge is actually working now as well. The only gauge left is the oil pressure. With the key turn on, but not started it shows 0. However as soon as I start it,it pegs out. What gives?

Online bd

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Re: Switching to gauges. Need help!!!!
« Reply #7 on: August 04, 2012, 05:26:19 PM »
That sounds more like a faulty (or the wrong) oil pressure sending unit.  Your sender should look like the one below.  Here's a link to an oil sender for your application (assuming your gauge is 0-60 PSI)...
http://www.autozone.com/autozone/parts/Duralast-Oil-Pressure-Switch/1979-Chevrolet-C10-1-2-ton-P-U-2WD/_/N-imf3zZ9ciau?itemIdentifier=158014_124004_0_5673

Disconnect the wire from the sender.  With the key ON, engine OFF oil gauge should be pegged past maximum.  Next, ground the sender wire with a jumper; gauge should drop to 0.  If it does, the sender is probably faulty.

For a more accurate test of the sender - if you have an ohmmeter, with the gauge wire still disconnected from the sender, connect the ohmmeter between the sender terminal and a good ground.  With the engine OFF, the ohmmeter should register 0 ohms.  Start the engine - the ohmmeter should register somewhere between 0 and 90 ohms.  If the sender doesn't register as described, it is faulty.

If you want a more accurate test of the dash gauge, insert a 45-ohm resistor between the sender wire and ground with the key ON, engine OFF and the gauge should read about 1/2-scale, or ~30 PSI for a 60 PSI 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)

Offline bgarr01

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Switching to gauges. Need help!!!!
« Reply #8 on: August 05, 2012, 10:43:03 AM »
I checked and I have the right sending unit. In your directions it states that when you have the wire unplugged and key on it should be pegged out. Mine isn't its sitting right at 0. When I start it it pegs out. I checked it with an ohmmeter it it bounces around all the way up to like 120s. Does this mean the sending unit is bad?  Also I noticed my volt meter is right when I start the truck, but as soon as I give it gas It goes up to the line before red and doesn't come back down?  What would be the issue here?
« Last Edit: August 05, 2012, 10:54:41 AM by bgarr01 »

Offline bgarr01

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Switching to gauges. Need help!!!!
« Reply #9 on: August 05, 2012, 12:53:29 PM »
I went and bought a new oil sending unit and no luck here. Still pegs out. Does the exact same thing. Starts at 0 with key in on position not started. As soon as I start it it pegs out. Also bought a temp sender and it's to big. Guess I'll be going back.

Online bd

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Re: Switching to gauges. Need help!!!!
« Reply #10 on: August 05, 2012, 12:57:45 PM »
Let's check one thing at a time...

All of the gauges in the instrument cluster connect to the flexible printed circuit board (PCB) on the back of the cluster housing, via 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.

Voltmeter:
* Using your multimeter, measure voltage at the battery with the key OFF.  A fully charged battery will register 12.6 volts.
* With your multimeter still hooked up across the battery, set the park brake and start the engine.  Watch the multimeter as you raise the RPM.  A correctly functioning charging system should produce ~14.2 volts across the battery.  If it registers over 14.5 volts, you have a charging system problem.  Look at the voltmeter in the dash.  Does it agree with the multimeter reading?

Oil Pressure Sender:
The sender is a rheostat (variable resistor).  One end of the rheostat connects to the sender terminal, the other end of the rheostat connects to the sender housing (ground).  The rheostat (sender) changes its resistance in direct proportion to oil pressure.  At zero pressure, it has zero resistance (essentially grounding the wire from the gauge).  At full scale (60 PSI) the sender has a resistance of ~90 ohms.  At half scale (30 PSI) the sender has a resistance of ~45 ohms, and so on.  The resistance of the sender should vary smoothly with oil pressure between 0 ohms (0 PSI) and ~90 ohms (60PSI).  When you remove the wire from the sender, you introduce infinite resistance to the gauge circuit and the gauge pegs past maximum pressure.

But, be certain that when you are using your ohmmeter, you are measuring across a "dead" circuit.  An ohmmeter will not measure correctly if connected to a circuit that has power running through it.

Oil Pressure Gauge:
From your post, I suspect that the circuit connections are not quite right.  The oil pressure gauge requires ground [ckt 150 - blk], ignition [ckt 39 - pnk/blk], and sender [ckt 31 - tan].  You need to verify the correct circuit connections to the gauge.  Visually trace the foil circuits of the PCB on the back of the cluster, from the harness connector to the back of the oil pressure gauge.  Use your multimeter and verify that the wires in the connector are, indeed, ground, ignition, and sender, properly wired to the gauge.

Temp Gauge:
Did you verify temp gauge operation by unplugging then grounding the sender wire?
« Last Edit: August 05, 2012, 01:02:12 PM by bd »
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 #11 on: August 05, 2012, 02:22:48 PM »
I checked the volt meter vs battery and it seems to be correct. The battery read 14.7 and that's roughly what the gauge shows.

I believe the temp gauge will work correctly once I receive the proper temp sender.

I checked the ohms at the unit and it shows ~60 ohms. I did like you mentioned and checked the power wires, ground wires, and sending unit wires. Power all has power. Ground is all ground. The sending unit wire has 12.4 volts with the key on and truck started. Should this have any power to it?

Online bd

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Re: Switching to gauges. Need help!!!!
« Reply #12 on: August 05, 2012, 04:32:44 PM »
I checked the volt meter vs battery and it seems to be correct. The battery read 14.7 and that's roughly what the gauge shows.

14.7 volts with engine running is okay as long as it doesn't charge over that.

I checked the ohms at the [oil sending] unit and it shows ~60 ohms.

I assume this was with the engine running and the tan sender wire unplugged.

I did like you mentioned and checked the power wires, ground wires, and sending unit wires. Power all has power. Ground is all ground. The sending unit wire has 12.4 volts with the key on and truck started. Should this have any power to it?

With the key on, the sending unit wire from the gauge will register voltage (the wire is actually receiving power from/through the gauge).  BUT, if you measured 12.4 volts on the sender wire with the harness connector unplugged from the cluster, you discovered your problem.  The tan sender wire should not register any voltage if it's unplugged from the instrument cluster. 

It sounds like you're narrowing it down to just a couple of possibilities.  You should be able to see some light at the end of this tunnel.
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 #13 on: August 05, 2012, 05:33:12 PM »
Awesome. Bd you've been so much help. Don't know what I would have done without ya. One last question. Where Wouk 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. Man electrical stuff sucks.

Offline bgarr01

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Switching to gauges. Need help!!!!
« Reply #14 on: August 05, 2012, 08:00:14 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.