94 blazer volt gauge reading low.

[blwn71]

hello all i have a 94 blazer that i have owned for about 2 years.i have replaced the battery twice,and the alt once.but my gauge still reads low.i have cked the volts coming out of the alt and to the battery,they read 14 or better even when i turn on the headlights and ac.by the gauge inside my truck it shows around 12 or so when i turn on lights and ac.i hooked up a scanner to my truck and it shows 12.9 volts to computer. know i saw a simular post on here awhile back but never got back to reading it.any help would come with many thanx.could it be a grounding issue?gonna sound messed up but i am an ase certified tech and this has me stumped.

 

[bigblock72]

No worries, the gauge is off about a volt or so. Just about every 92-94 I've seen has the same problem and isn't worth worrying about.

 

[blwn71]

its aggravating me every time i use my signals my needle starts to bounce or if i run the ac,lights,and wipers it looks like i have no power left.just one of those things that eat at you until you figure it out.its like the buzzing sound in your speakers when you install an amp or new radio,until its grounded properly.

 

[bigblock72]

You can try adding another ground from the firewall to the engine and see if that helps.

If that doesn't do it then all you can do is pull the cover off of the cluster carefully remove the needle and reinstall so it reads accurately.

 

[dhcomp]

You can try adding another ground from the firewall to the engine and see if that helps.

If that doesn't do it then all you can do is pull the cover off of the cluster carefully remove the needle and reinstall so it reads accurately.

I did this ground mod, and it helped steady the gauge a little. Go to the battery section at walmart, get the largest, longest cable they have, its like a 4ga lawn and garden battery cable, buy an additional pair of lugs, cut cable in half, add lugs, run a cable from battery to frame, then another from teh same bolt from frame to body. Total cost is under $15. Make sure all your connecitons are clean. You'll see some electrical benefits if you are sensitive to your truck.


I wouldn't mess with the needle though. Then you're gonna know you moved it and never trust it anyways.....

 

[McDOT]

Just a quick note to make sure your alternator belt is tight. Very tight ! ! ! With your engine shut off, try and manually turn the alt pulley by hand. If you can turn it by hand with the pressure of the belt, tighten the belt more with a big-ass screw driver to leverage the operation. I would also add that if you are in a cold climate, warm up the motor and then shut down to test the tightness and adjust. Things expand once they are warmed up and the belt may start slipping after a time. I just went through this if you haven't guessed... got a nice new red top optima in the process though The original battery did test weak though and the truck is new to me and the weather here is - 40 C so didn't want to fool around with unknowns. Hope this helps. Let us know

 

[dyeager535]

If the alternator output is a constant 14 volts, or close when under heavy load, you don't have an alternator problem.

Any problem that you have with low voltage NOT the fault of the alternator, is likely going to be due to connections...either grounds for the individual components (gauges, lights, etc) or connectors that feed power to them.

It is not uncommon to lose voltage of up to 1.5V through all the wiring, but it is uncommon for the needle to fluctuate with the turn signal, since the draw on the electrical system is minimal. I would expect a gauge cluster connector/ground issue.

Factory grounds are more than sufficient (most are redundant) IF the connections are good and you aren't asking them to do much more than what came stock.

 

[dhcomp]

If the alternator output is a constant 14 volts, or close when under heavy load, you don't have an alternator problem.

Any problem that you have with low voltage NOT the fault of the alternator, is likely going to be due to connections...either grounds for the individual components (gauges, lights, etc) or connectors that feed power to them.

It is not uncommon to lose voltage of up to 1.5V through all the wiring, but it is uncommon for the needle to fluctuate with the turn signal, since the draw on the electrical system is minimal. I would expect a gauge cluster connector/ground issue.

Factory grounds are more than sufficient (most are redundant) IF the connections are good and you aren't asking them to do much more than what came stock.

My 94 ALWAYS fluctuated with the turn signals. Got a little better with added grounds, but still did it.

 

[blwn71]

sorry guys i have been rapped up in moving job change and sick kids...still have the blazers and thanx for the input for my 94 i will try the ideas you have left for me and let you know how it goes.....i also have picked up a couple of 71 chevelles that i am trying to round up parts for so i can get one built...as you can tell i am spreading myself pretty thin..lol

 

[Fordum]

When you get your life taken care of and have some time, grab a voltmeter, and re-post.
Me or somebody here will talk you through a couple of tests to see if you have a problem or a lying meter.

Haven't worked on a GM, but I had my Ford dash apart a couple of years ago, and I calibrated my voltmeter while I was in there.

I have a very accurate power supply, so I set it on 14.00 volts, hooked my meter to it, and put the needle on the shaft exactly on 14 volts.

Then, just for fun, I ran it through its range. It was dead on.

I suspect most meters are plenty accurate enough, they just need to be set.
If you set them out of the cluster, with a known voltage, then any discrepancy after that is going to be a truck problem.

 

[EIB8400]

My 96 does the same. With the heat on high, lights on and wipers going my guage will drop down to about 9 if I sit at a light for a while. I haven't really looked into it. I thought I just got a crappy alt from advanced.