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Discussion Starter #1
So I'm trying to get the dash gauge to work again and i need a new sending unit, but holy crap...60 bucks?!

Does anyone know if a more modern sensor will work instead? I found some NOS Napa sensor units at an old junk yard with the same 3 prong configuration and 1/8 npt nipple, Napa part# OP6625 and OP6626.

Also, I have this issue
335886

Loose wire is tan or light brown. Where is it supposed to go?

Thanks
 

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Discussion Starter #5
It goes into the same wire loom as the oil pressure switch and sending unit wires. I found a diagram and it shows a tan wire coming from the oil sensor, however neither plug has a broken or missing wire.
 

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I can look at mine if I can remember to do that.
 

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Oh and did you check rock auto?
 

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Discussion Starter #8
I'd appreciate you taking a look at yours when you get the chance, thanks!?

Yes, rockauto has them...40 - 60 bucks tho? I'm going to try a junkyard part first.
 

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Sure thing. Also, you may want to check out a profile deathphoenix99 . He has wiring diagram link in his signature that has a TON of stuff on it. Hard comprehending that Rock Auto is that high. They are usually the lowest.
 

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Discussion Starter #10
So I found the oil pressure sender that came out of this truck (it was in the bed with along with other junk, lol ) and bench tested it. The ohmmeter moved when I applied air pressure to the oil orifice so I reinstalled it. The gauge doesn't peg out at 80psi anymore but it twitched above zero for a second.

So I'm thinking this lose tan wire is the problem.

Jimmykicker, did you get a chance to look at yours?

I tried grounding it to the body, as I had it touching ground when the gauge twitched, however with a good ground connection the gauge still doesn't work. The wiring diagrams say a tan wire goes to the instrument cluster (pin 2) but I still can't find the other end of this wire.

I have a mechanical gauge installed under the hood, so I know I've got good oil pressure.
 

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Sorry about the late reply but I just found this thread and joined in to help.

So I'm rebuilding a burnt wire loom for an '88 and have found a bunch of diagrams and schematics. The tan wire coming from 3 wire oil pressure switch goes to the bulkhead connector located on the driver side of the firewall. The pin designation is "D2". On the cab side it goes directly to your gauge cluster pin "2". Circuit # 31.

1) disconnect the battery (-).
2) ground the loose (-) terminal to the (+) terminal for 3-5 minutes. This ensures there is no residual power in the system to cause problems with the computer as you follow the rest of the steps. (please PLEASE make sure the battery is disconnected FIRST!!!)
3) disconnect the bulkhead connector (be careful with the clips)
4) look at the attached diagram. The cyber looking Pac-Man plug is facing pin on (wires behind). They are designated A-H running bottom to top and 1-3 left to right.
5) test continuity from "D2" to the tan wire on your oil switch. If it doesn't read then you'll have to look for where they have separated.

I know this is late but I hope it helps
 

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hmm, this is kinda old but well anyway.
there are 2 tan wires in the loom. one is used when you have the guage package the other is used if you only have idiot lights. they both run to the idiot light (oil pressure) in the dash
 

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One sensor is for the dash cluster, either light or gage. The other goes to the computer. This is before they integrated the system to handle 1 sensor for both
 

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Discussion Starter #14
Sorry about the late reply but I just found this thread and joined in to help.

So I'm rebuilding a burnt wire loom for an '88 and have found a bunch of diagrams and schematics. The tan wire coming from 3 wire oil pressure switch goes to the bulkhead connector located on the driver side of the firewall. The pin designation is "D2". On the cab side it goes directly to your gauge cluster pin "2". Circuit # 31.

1) disconnect the battery (-).
2) ground the loose (-) terminal to the (+) terminal for 3-5 minutes. This ensures there is no residual power in the system to cause problems with the computer as you follow the rest of the steps. (please PLEASE make sure the battery is disconnected FIRST!!!)
3) disconnect the bulkhead connector (be careful with the clips)
4) look at the attached diagram. The cyber looking Pac-Man plug is facing pin on (wires behind). They are designated A-H running bottom to top and 1-3 left to right.
5) test continuity from "D2" to the tan wire on your oil switch. If it doesn't read then you'll have to look for where they have separated.

I know this is late but I hope it helps
Wow, thank you for this. I'll get this fixed next time I get a chance. This truck has had to pull daily driver duty lately, as my car died permanently.

Sorry for the late reply, I've been extremely busy.
 

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hmm, this is kinda old but well anyway.
there are 2 tan wires in the loom. one is used when you have the guage package the other is used if you only have idiot lights. they both run to the idiot light (oil pressure) in the dash
So, should they both go to the same contact on the plug or one unused and that end should have an insulator on it?
 

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So, should they both go to the same contact on the plug or one unused and that end should have an insulator on it?
3 wires on 1 plug: tan goes directly to the bulkhead connector... that is the gauge/light signal in your cluster; tan/white connect together both sensors and splice into a bunch more going to the fuel pump relay, fuel pump prime/check connector, bulkhead connector and the computer; orange connects both sensors and splices 2 to the computer and another to the fuel pump relay. You may have an oil pump relay if you have an auto trans... the tan/white and the orange will go there too.
 

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so yes the other tan wire is unused. at one time it had a connector on it but probably corroded off. just tape it up
 

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Ok. Here's what I had and what I did. See the 2 sensors? The wire colors I had and where they connected were as follows:
Oil Sensor 1 (2 wire): Tan/White to fuel pump, fuel pump relay (pin B), fuel pump test/prime connector, bulkhead connector (pin E1) and to the ECM (pin B2); Orange to fuel pump relay (pin E), ECM (pin B1 and C16), Bulkhead (pin G1).

Oil Sensor 2 (3 wire): Black to oil pressure relay (pin B); Brown to oil pressure relay (pin C); Tan to bulkhead (pin D2).

Since I had to collate all the messed up, contradictive information (including Chevy/GM's own manual) to get this right, I ended up making my own spreadsheet. If the color code you have for your oil sensors is what I have pictured here, then this is how it's wired (nominally for pressure gauge in dash cluster). The other way I posted is if they both have tan/white and orange wires (for pressure light in dash cluster).
 

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