volt gauge reading

[allproroofing]

Got a small voltmeter reading problem with a couple other quirks. I have tested my alternator and it puts out 14.7 volts , but my gauge reads about 12 in the truck. While driving down the road , or idling in the driveway for that matter , it will occasionaly jump up to around 14 volts on the gauge. I have also noticed when turning the headlights on , there is sometimes a delay with when the gauge lights come on. Noticed the windshield wipers sometimes don't like to work unless I play with the switch a little. I have a new alternator and 2 brand new batteries. Any ideas what could cause this? All my underhood grounds seem to be good.

 

[Matt Bachand]

Grounds 'SEEM' to be good isn't good enough. Read the GROUND thread thats here. Remove, wirebrush, both ends, and mounting surface, and re-install ALL grounds.

Pay special attention to the ground strap that goes from PS Intake bolt behind the downpipe. This connects block to frame, and there is another there goes block to cab. replace those if in question, they burn up easy. Poor design.

Defanately sounds like a ground problem. Visual inspection isn't good enough.

 

[Missy Good Wench]

Check the Power feed to the chassis feed lug in the junction box.

Make sure you have good 14V there.

Many times the feed wire from the main battery cable will corrode in the main cable "crimp zone" and the result will be all sorts of "hinky schtuff a happnin"

The early trucks 92-94 fed the power off the RH battery, down around the starter, up behind the engine and into the junction on the firewall above the AC unit.
The early trucks feed from the alternator to the LH battery.

95 and later trucks feed power off the LH battery back to the fuse/breaker and junction box behind the ABS unit.

Power feed from the alternator to the LH battery on the 95

96 and later trucks changed a bit as the alternator moved to the RH side of the engine.

The dash gauges are or can be flakey as the input to these is a slip in connector behind the cluster.

There are a few small screws that hold the entire cluster in the dash "Bucket"
Remove the screws and the whole cluster slips right out.
There is a large "GANG" plug in the back withlittle copper tabs on the mylar circuit panel.

Make sure all the tabs are clean and can make good contact.

Volt meters are notorious for being hinky in the GMT400 trucks.

The older units 73-91 in the blazers and burbs and 73-87 in trucks were fairly good about working and fairly good accuracy wise too.
Nice part of the old clusters was that you could replace just one meter at a time if need be.

Not so on the later ones.

If in doubt about the ground, install a fresh one on the LH side that connects the body/engine and frame together.

This will eliminate any issues there.


Good luck


Missy

 

[allproroofing]

Thanks for the tips , I'll inspect everything in the morning and let you know what I found

 

[STEVE53]

I was having similar issues with my oil pressure and temp gauges. Oil pressure would show 60-70 psi and suddenly show 20-30. Temp gauge would also show that I was running hot, then show normal. I removed the gauge cluster and used some 1500 grit sandpaper to LIGHTLY clean the terminals in the dash and on the cluster, as they showed a little corrosion. Since then the gauges read steady. My volt gauge does about the same as yours, so the problem could be elsewhere.

Steve

 

[allproroofing]

anyone know exactly where the volt gauge gets its power from? fuse block maybe?