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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: fst_orange on March 25, 2015, 11:52:14 pm

Title: Oil Gauge Rage
Post by: fst_orange on March 25, 2015, 11:52:14 pm

Hi all, I'm new to the forum and have started on a project. I've got an 85 Chevy K20 I'm trying to get fixed up. The oil gauge doesn't work. It pegs to zero soon as I switch it on and stays there while running. I tried another gauge as well and it does the same thing. Could someone explain to me how the oil gauge circuit works please? I'm pretty sure the sending unit is definitely a resistor of some sort I just don't understand the way it works. It's a two wire sending unit and the gauge has three wires. I've read schematics and can't make heads or tails of them I'd like to know how power is distributed between the sender and the gauge. Thanks a ton.

Title: Re: Oil Gauge Rage
Post by: hatzie on March 26, 2015, 12:53:55 am

The sending unit is a pressure transducer.  The resistance varies from 0-90Ω. 0Ω=0psi 90Ω=60psi
The 1985 should have two senders.  The 2 wire sender is a pressure switch for the choke. The switch has 2 blue wires and one pink wire. The gauge sender has one Tan wire.

Title: Re: Oil Gauge Rage
Post by: fst_orange on March 26, 2015, 04:05:39 pm

Thanks a lot man! I found it and replaced it. It's lost ground now i've got that narrowed down to a burnt spot in the circuit board. I'm sure it happened while i was trying to figure out the circuit. One of my buddies made sparks with it by accident lol. Oh well.

Title: Re: Oil Gauge Rage
Post by: frotosride on March 26, 2015, 05:33:01 pm

Quote from: fst_orange on March 26, 2015, 04:05:39 pm

Thanks a lot man! I found it and replaced it. It's lost ground now i've got that narrowed down to a burnt spot in the circuit board. I'm sure it happened while i was trying to figure out the circuit. One of my buddies made sparks with it by accident lol. Oh well.

If you want a cheap fix without having to solider in a jumper you can get a small thing of window defrost repair. Its basically ligiud copper. Just tape along the area you need the circuit to run paint it and let it dry..bets the heck out of buying new boards or a whole new cluster.

Title: Re: Oil Gauge Rage
Post by: Irish_Alley on March 27, 2015, 12:43:41 am

Quote from: frotosride on March 26, 2015, 05:33:01 pm

Quote from: fst_orange on March 26, 2015, 04:05:39 pm

Thanks a lot man! I found it and replaced it. It's lost ground now i've got that narrowed down to a burnt spot in the circuit board. I'm sure it happened while i was trying to figure out the circuit. One of my buddies made sparks with it by accident lol. Oh well.

If you want a cheap fix without having to solider in a jumper you can get a small thing of window defrost repair. Its basically ligiud copper. Just tape along the area you need the circuit to run paint it and let it dry..bets the heck out of buying new boards or a whole new cluster.

nice never even thought of that, have to do that

Title: Re: Oil Gauge Rage
Post by: fst_orange on March 28, 2015, 11:36:23 am

i got it fixed. I tracked down another instrument cluster with bad gauges and swapped mine into it. Works like a charm now. I'll keep that window defroster repair trick in mind. That's really cool.