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Light To Gauges Question (Couldn't Find Answer)

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MrFlippers

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First post so I will start off by saying Hello. My father in law has an 87 k5 that I have been converting to Gauges from the Dummy Lights and there are a few questions I have (researched and couldn't find the answer so decided to post)

First off I know on the 87's there was the oil pressure switch next to the distributor, and the oil pressure sender on top of the filter. The sender on top of the filter is supposed to hook up to a tan wire, but for the life of me I cannot locate the wire that goes to it. Where would it be???

Second, the coolant temperature gauge works just fine however when I crank it the gauge jumps around which is odd to me. Is this normal or not?

One last thing, not so much gauge related, but when the headlights are on both turn signal lights on the cluster are lit up. Also the marker lights and running lights don't light up when the headlights are on. With the lights on if I use the turn signals they all light up but they stay solid. I have tried a known good headlight switch, I can also hear the flasher clicking so I have eliminated those two things.

Thanks for the help, hopefully this is the right place to post this, if not I apologize.
 
Thanks for the help. Read through it. I need to find the wire in the engine bay that goes to the oil pressure sender. Idk where it would be, and I am unsure if it is one of the wires that goes to the factory switch. Buddy has an 87 suburban with factory gauges and I have looked at it and see the wire but can't see where it goes. I assume the temp is because of a ground but am not sure as well. Any chance that the turn signal switch would cause all those light problems?
 
You can just run a new wire of your own if you can't find it.

Martin
 
Yeah that's what I might have to do, or trace the wire all the way from the cluster down and find it (pin 3 is has a tan wire connected at the cluster connector so I know there's a wire somewhere.
 
I had looked in to this on my 87 K5 and I know there are wires in the cluster plug you need to swap. You also need to switch the sending units on temp and oil. I will try to find my info and post it. If I can only remember where I put it.
 
MrFlippers said:
First off I know on the 87's there was the oil pressure switch next to the distributor, and the oil pressure sender on top of the filter. The sender on top of the filter is supposed to hook up to a tan wire, but for the life of me I cannot locate the wire that goes to it. Where would it be???

Second, the coolant temperature gauge works just fine however when I crank it the gauge jumps around which is odd to me. Is this normal or not?

One last thing, not so much gauge related, but when the headlights are on both turn signal lights on the cluster are lit up. Also the marker lights and running lights don't light up when the headlights are on. With the lights on if I use the turn signals they all light up but they stay solid. I have tried a known good headlight switch, I can also hear the flasher clicking so I have eliminated those two things.
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Well if the truck had idiot lights, it would be a switch, not a sender. Any chance the wiring colors were different? As mentioned, if it's not there, run a new one.

I don't notice my temp gauge jumping when cranking. If it reads ok I probably wouldn't worry about it, if you didn't have to run extra wires to power it. Factory wiring should be sufficient for power/ground. As MetroDPS mentioned, you need to make sure the Instrument Panel (IP) connector matches up to the pinout of the cluster itself in any case.

As to lights, always start with the easy stuff. Make sure *all* bulbs are good (markers, signal, brake, reverse, etc) and the proper ones for each position. If those all are good, it's often a ground issue. If there is hacked up trailer wiring, fix that and see if the problem resolves itself.
 
OK I did not read ALL the threads but these are the ones I saved for your topic. Membership pays for its self real fast. You should consider it when you get a few bucks together.

swapping guages?

Idiot lights, switching to gauges?

Dash gauges, 82 to 86 swap. is it possible??

Anyone ever switched from lights to gauges

Russell said:
No one ever claimed switching clusters was easy man :) Its a pretty in-depth swap electrically speaking! However, I'm fairly sure we can get it figured out between the two of us :)

First things first, you'll need to do some wire tracing. To do this, you need a test light so you can see if the light comes on in the engine compartment and a known 12 volt source from inside the truck (any of the pink & black, first color being the dominate one, the other a stripe, wires will have 12 volts with the key on) so you can figure out which wire on the cluster connector connects to which sending unit wire in the engine compartment.

This job isn't quite as scary as it may seem, as you can quickly identify, and tape back several wires right off the bat.

First is your seatbelt wire. It has been yellow in all my trucks. When you turn your ignition on, it should provide 12 volts to turn on the idiot light.

Second is your turn signals. They are light and dark blue, located right beside eachother on the connector. They will have pulsating voltage with the signal lights on (remember which is which!)

Third is your highbeam indicator. They have been bright green on all my trucks, should have 12 volts when your highbeams are on

Fourth is all the hot on ignition wires, which are pink and black, and all have 12 volts on ignition on. (straight pink is NOT a power wire)

Fifth is your ground wires, they are all black and white. Easily identified by using a multimeter, and checking continuity between them and any good ground in your truck.

Sixth is your dash light wire, which is grey, and has 12 volts on when you turn your running lights / dash lights on.

Seventh is your brake idiot light, which is usually a tan / white wire, and can be tested by checking for ground on it when the e-brake has been pushed down.

Eighth is your SES idiot light, which should have ground when you turn your ignition on, activating the ECM.

Now, once you've got all these pulled back, there will not be very many wires left, and within them will be your 3 gauge wires, and depending on how the electrical speedometer hooks up, wires for it too. So, before we go over chasing wires down, lets go over what each of the gauges needs:

First gauge is the temp gauge. It needs a hot wire, ground wire, and the signal wire from the engine head. When its hooked up correctly, it will peg way past 0 without any input from the signal wire, and will peg all the way to the other side if you ground the signal wire. It usually has a green sending unit wire.

Second gauge is the oil pressure gauge, which has the same needs, and behaviour as the temp gauge wire. It may share power and grounds with your temp gauge, check the circuit sheet to find out. Usually has a tan and white sending unit wire.

Third is your fuel gauge, which again, is the same as the temp and pressure gauges. Usually has a straight pink sending unit wire.

Fourth is your volt meter, which needs a hot wire on one terminal, and a ground wire on the other.

So, now that you know all the requirments, you can chase down the sending unit wires. Simply apply 12 volts from one of the pink and black wires to the wire inside of the dash cluster connector (making sure that you've unplugged all the sending units on the engine!) and poking a test light in the end of the engine side connector, and the other side of the light to ground. If it lights up, you know which sending unit that wire is for, and you can then tape it back.

Once you've got all your wires figured out, you can then check all the circuits on the back of the printed sheet, and start pinning everything out the way it needs to be on the new cluster.

It takes a few hours, but is well worth it later :)

If you don't want the old idiot light sending units, lemme know. I've got full gauges right now, but I'd like to install a Check Gauges light on my truck, which involves installing a few idiot light sending units that'll turn it on :)


Oh, one more thing. Dash cluster connectors have gotta be the biggest pain in the butt of any on our trucks. You need to take a paper clip, bend the very tip if it over about 35 degrees, then hold the wire as far into the connector as it'll go, slide the paper clip in, then rotate it so the bent part bends the connector's pin in, allowing it to slide out. It takes some practice, but it isn't impossible :)

Good luck, and lemme know if you've got any more questions. Sorry I can't help you much with the speedo, but I've never seen an electric one in person.
Click to expand...
 
Thanks for the input, I am on my way over to work on it, I will post back up if I solve any of this. Btw it does have a trailer harness that looks disconnected so I might start there.
 
Found the wire!!!! There was another sensor that looked identical to the oil pressure switch above the oil filter that was covered in old oil so I didn't see it the first couple times :doah::doah::doah: . Anyways, put the new sensor on (looks like a silver can) and fired it up. When I turn the key on the gauge goes to 80, when I fire it up the gauge goes past 80 a bit. Tried the other mint cluster I have and it does the same thing.

I read one of the links that was posted up here and it gave me this

1. light green: hi beam indicator
2. Grey: dash illum
3. black: volts /dash illum
4. pink/black tracer: volts
5. tan: oil sender unit
6. pink/black tracer: oil, temp and fuel gauges
7. pink: fuel sender
8. black: fuel ground/ illum
9. green: temp sender

18. pink:
17. dbl tan/white tracer: brake light
16. pink/black tracer: check engine
15. black: check engine ground
14. BLANK(empty)
13. yellow: seat belt light
12. dark blue: right turn indicator
11. light blue: left turn indicator
10. black: illum ground

Everything lines up except I do not have a pink/black tracer for oil temp and fuel (pin 6.) Do not have a wire in the harness anywhere for this, is this basically just a ground??
 
The pink with black tracer is the 12V (+) that comes on with the ignition switch to power the gauges.

The problems you describe with the turn signals and running lights are likely caused by a poor ground somewhere in the wiring. Trace ALL ground wires in the lighting harness to rule out a bad connection. A bad ground can cause strange issues in 12V systems...
 
There are 2 different sending units for oil pressure gauges,one with 0-60 psi gauges and another for gauges that go to 0-80 psi on some years and models...sender and gauge must match up to give proper readings..
 
+1 to diesel4me.

AFAIK only the diesels had 80PSI units stock, the gas trucks got 60. Senders are indeed different.
 
I have the 0-60 and 0-80. Both max out when I turn the key on and go further still when I start it. That pink black wire powers the gauges?? What would I run it to if I did not have the wire in my harness? Its an ex border patrol truck so Idk if that makes a difference.

The gauges all work as of now, just the oil gauge maxes. I will check all grounds.

Are there any common grounds that go bad on these trucks?? I know on his 95 c1500 he had a ground go out towards the tailgate that caused no rear lights.

Thanks for all the help btw.
 
If the gauge is maxing out, its a sending unit/sending unit wire issue. I can never remember which is which. If sending unit wire is grounded, gauge will peg one way, wire "open", the gauge will peg opposite way.

Do you have an actual gauge sending unit? You can't use the idiot light switch. Completely different function.

You should be doing this with a voltmeter in all honesty. Really bad idea to guess which wires are which. I don't know how the idiot lights are wired, but I'd expect for instance the oil pressure light is 12V with key in run position, so that wire could power all the gauges (but use a meter to make sure). There have to be some ignition hot wires to the cluster already, as the fuel gauge and idiot lights had to get power somehow.
 
There was the oil pressure switch that was there currently. Replaced it with the correct oil pressure sensor and used the same wire. I will be checking all grounds on it when I get another day off. If everything checks out I will take the oil pressure sensor I bought back and exchange it for another one, just to see if that works.
 
Don't take it back without checking your wiring. Ground the wire to the gauge from the sender, then open it. If the gauge doesn't "max out" below 0 and over 60/80 with those tests, the gauge/sender wiring is at fault, not the sender.

Very easy test. All gauges test/work/respond the same way, except voltmeter of course.
 
WAIT! there is one up by the distributor on the back top and the one by oil filter is a kill switch. did you replace the top one?
 
Yeah on EFI vehicles there is a second oil pressure sender for the computer near the oil filter--the gauge unit is located behind the distributor..

I doubt a parts store will take back used electrical parts too--none here will,even if you never installed them!..
 
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