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Gauge Problems...

GMC Guy

GMC Guy

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well first off, my oil pressure gauge always reads 60+ even after a fresh oil change and filter. i'm thinking maybe sending unit?

also the voltmeter barely hovers above 8 volts. but i've never had a problem with the truck not starting (knock on wood). so i'm guessing that the alternator isn't charging enough..?

the speedo and engine temp gauges seem to be working fine, so i'll keep my fingers crossed....

any help is greatly appreciated.
 
its your oil sending unit change it out then start it up give it a few then oil gauge should work fine ....As for you voltage meter I really am not not sure !!!! Sorry
 
update on the voltmeter: worked fine today, read right at 13 volts...maybe it's just bad connections :confused:

as for the oil pressure sending unit.... not quite sure where it is...:o i've never changed one out, and i'm assuming you can pick a new sender up at a local auto parts store?
 
on mine the sender is on the block above the oil filter. i think $30 at auto parts store. the T and the copper line run to a mechanical guage i mounted under the dash because i just don't trust electronics.
 

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interesting i love electronics lol (im a computer wiz) i would say check all your connections, and make sure stuff is all working the way it should be :)
 
On my 4.3 and my 6.2 the oil pressure sending unit was located up at the back of the intake by the driver's side head. Parts store should have them or be able to order it for you.

The problem with electrical gauges is that the sending units and wiring connections can go bad, especially the stock gauge cluster circuit, and give you an improper reading. Mechanical gauges tend to be more reliable.
 
i think i found where it is, i'm pretty sure mines next to the distributer on the right side...should be fun getting to :rolleyes:

are there any "tricks" to changing one out? i just dont want oil leaking everywhere if i pull it out..
 
The sender shouldn't leak much oil - maybe a few drips- when you change it. Just don't do it right after you turn off the truck. Let the oil in the block drain back into the oil pan first. I put Teflon tape on mine and have no leaks.
 
ok so today i replaced my alternator and oil pressure sending unit in hopes to cure my gauge problems...but even after the new parts went in and i let the truck run for a little while, nothing changed with my gauge readings. the voltmeter still read like 9 volts and the oil pressure was past maxed out. :confused: :confused:
anyone have any ideas?
 
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Check the alternator output at the battery. In a pinch, it can be tested by removing the positive cable while the engine is running. If the engine shuts down it was running off the battery. If it keeps running its running off the alternator like it should.

Sounds to me like you have poor connections some where in the system. To get correct/ accurate readings all connections need to be clean and tight.

Since you already changed both the alternator and oil pressure sending unit, the connections should be good there. Next go to the outside firewall wiring harness connector, clean and put dielectric grease on plugs before tightening.
Next move to the inside and check/ clean or replace the fuse for your gage cluster. Inspect the wiring for hack jobs and repair the best you can. Moving up to the back of the instrument cluster you'll find your next harness plug. It unplugs from the back, remove it, clean, grease and install.

On the back of the instrument cluster is a plastic solid state circuit sheet, you may have to remove the cluster (easier) to inspect the circuit and gages.

The OEM speedo it is a mechanical gage and OEM water temp is electrical.

Test before buying electrical parts, most are non refundable.



dh
 

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so a friend of mine suggested that i check the ground for the gauges, a poor ground could cause the gauges to not function properly. soo now my question is...does anyone know where i might find the ground for the gauges? or at least a probable location. thanks
 
GMC Guy said:
so a friend of mine suggested that i check the ground for the gauges, a poor ground could cause the gauges to not function properly. soo now my question is...does anyone know where i might find the ground for the gauges? or at least a probable location. thanks
Click to expand...

On the left side of the cab firewall, above the parking brake mechanism. Some have a W shape grounding block bolted to the side firewall, this will accept up to six spade type ground plugs.
 

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i found the ground, cleaned it up, and then noticed that the circuit board wasn't tight because of some of the light bulb connectors were loose. so i just tightened them up and WALA! all the gauges worked perfectly. thank you all for your advice.
one problem solved... :)
 
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