94 Yukon - Electrical Weirdness

================== All your readings look good. Try putting a load on it with lights, A/C ect. while idling then check it again. You really need to load test the battery and alternator to know for sure if there is a problem. You cant trust the dash gauge. After all it says 10v and your meter shows 13? You might want to clean ALL the battery cables (I mean all the positive ones). Split them apart from each other to clean the spacer and cables. 10volts while cranking is not bad, but the best test is the starter's draw in amps. There is such a thing a starter shims (not washers). It would be a good idea to have a look at the ring gear while the starter is loose and your trying a shim to quiet it down . Try a thin shim first so you know you didnt shim it too far on the first try. GL

. . . .

James=A0Sutherland........ strolled into the NG, chunked his keys on the desk, refused to sign the work order, and put forth this................

=3D=3D=3D=3DVehical Specs (available)=3D=3D=3D=3D

94 Yukon

=3D=3D=3D=3DCUSTOMER COMPLAINT=3D=3D=3D=3D

Voltage is a bit low (dash gauge 10v or so) under full load (AC, blower and lights on) at idle, the difference in voltage between the alternator and the battery seems high to me.

=3D=3D=3D=3DRepair History=3D=3D=3D=3D

The alternator is new,

the starter, (the second new starter in a row)

the battery is about a year old (Sears Gold)

I've disconnected the negative lead where it bolts to the block and cleaned both surfaces really well

=3D=3D=3D=3DSecondary Symptoms=3D=3D=3D=3D starter is very loud and doesn't crank the engine as fast as you'd think it should, both acted the same

The starter isn't clunking or grinding, it sounds like a normal starter that isn't getting quite enough power except about twice as loud as you'd expect.

=3D=3D=3D=3DNonconfirmed Precheck Data=3D=3D=3D=3D (data incomplete)

taken with VOM's neg lead to the bat neg post

...... Engine at idle only dome lights on

=A0alt post: 14.23 =A0Bat: 13.70 (AC 0.02) =A0Cig Ltr: 13.42 ...... Engine off, only dome lights on: dropped slowly for about ten minutes

leveled off at 12.44 =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 While starting the engine the minimum voltage was 10.5

=3D=3D=3D=3DNonvalidated Wiring Schematic=3D=3D=3D=3D

...... three lines from bat pos term,

one to alt, one to starter sol, big one to starter. ..... The positive line for the body uses the post on the starter solenoid as a terminal block, it just bolts on to the same post as the line from the battery.

=3D=3D=3D=3DRandom Indicators of Ability=3D=3D=3D=3D (provided by Mr. Sutherland, vehical owner) As far as the starter goes I'm thinking maybe I need to shim it a bit? Just a washer between the starter and the block on each bolt? Maybe I need new battery cables? I've heard some have fusible links built into them that can act as a resistor when they get old. In this truck there are

=3D=3D=3D=3DSymptom Specific Test Question=3D=3D=3D=3D (provided by Mr. Sutherland, vehical owner)

Anyone have any thoughts? =A0=A0=A0=A0=A0=A0=A0=A0-James =A5=A5=A5=A5=A5=A5=A5=A5=A5=A5=A5 =A5=A5=A5=A5=A5=A5=A5=A5=A5=A5=A5 Mr. Sutherland,

First, let me thank you for allowing us here at alt.trucks.chevy, the oportunity to serve you and we would like to convey our earnest apreciation for your patronage, and your decision to choose our NG as the facility in which to address your vehical symptom concerns.

Now......... as to your specific symptom...........

Utilizing the above data and fact sheet information, I must tell you that it this time, we are unable to make a conclusive determination as to the direct cause of the symptoms that you have registered. The preliminary data IS however, indicative of an amperage draw scenario. This is not a conclusive finding, but is the initial area of concern. Unfortunately, in order to confirm or disallow any system components that may be failing to perform within known good and item specific parameters, it will be necessary for you to comit to a sensable aproach to the repair.

=3D=3D=3D=3D=3D=3D The following steps are being given for your concideration......

.... check the amperage draw on the 3 independent battery positive leads and the engine system supply lead off the solenoid.

with key off----engine off

with key on----engine off

during engine starting (with ignition disabled)

during engine running

... check the voltage/amperage of the altenator steadily and slowly increasing engine rpms

at idle

at 1000 rpms

at 1500 rpms

at 2000 rpms

then repost new data

(alternative) .... General Undefined Extreme Suggested Solutions

install a ground strap on the starter

replace bat neg. lead

replace all three bat pos. leads

retest system and compare results to original data findings

Marsh Monster ~takes a sip, and waits for the test results~ ~:~

Did a load test real quick tonight after I got home from work:

This is engine at idle with most everything on. AC, Blower on high, headlights, dome lights

Alt 14.2 Bat 13.6 (ac 0.02) Cig 12.5

So really that doesn't look to bad, however I really don't understand why I've only got 12.5 volts in the cab. I wish I could find the dash ground, but so far no luck on that one.

Also, and I've seen this before while on the road. While measuring the battery the voltage suddenly dropped from 13.6 down to 12.8, then back to

13.6 again. All in about a second or so. It did this three or four times, then stopped. The lights all got slightly dimmer when it happened. There was no evidence of an increased load. The AC compressor had been on that whole time, so it wasn't that.

I'll check the difference voltages like bobo suggests but I'm sure they're going to be much greater then half a volt, even without any major electric loads. The question is what do I do about it.

Once again I'm trying to avoid driving it into a shop and saying "fix it" because I don't want to spend the money. I could probably get the alternator tested for free at my local parts store. -James

. . . James, go ahead and have yer alternator tested.

The new info you posted leaves it highly, highly suspect.

hope it's still under warranty for you.

let us know, marsh monster ~:~

Re: 94 Yukon - Electrical Weirdness Group: alt.trucks.chevy Date: Thu, Oct 30, 2003, 4:51am (CST+6) From: snipped-for-privacy@retlaw.net (James=A0Sutherland) Did a load test real quick tonight after I got home from work: This is engine at idle with most everything on. AC, Blower on high, headlights, dome lights Alt 14.2 Bat 13.6 (ac 0.02) Cig 12.5 So really that doesn't look to bad, however I really don't understand why I've only got 12.5 volts in the cab. I wish I could find the dash ground, but so far no luck on that one. Also, and I've seen this before while on the road. While measuring the battery the voltage suddenly dropped from 13.6 down to 12.8, then back to 13.6 again. All in about a second or so. It did this three or four times, then stopped. The lights all got slightly dimmer when it happened. There was no evidence of an increased load. The AC compressor had been on that whole time, so it wasn't that. I'll check the difference voltages like bobo suggests but I'm sure they're going to be much greater then half a volt, even without any major electric loads. The question is what do I do about it. Once again I'm trying to avoid driving it into a shop and saying "fix it" because I don't want to spend the money. I could probably get the alternator tested for free at my local parts store. =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0-James

=========================== The voltage's sudden change must be the regulator in the alternator if the load didn't change. Seams your only complaint is the starter noise and cranking speed. You tested the battery while cranking and the lowest you saw was 10.5V at the battery positive right? I would be ripping that noisey, ring gear and battery eating thing off my truck right now! :)

The trick is that when you find something high, either fix it or run a new wire... for a chassis ground simply go buy a cheapo battery cable from an autozone or something, something with eyelets or something and run it from someplace on the engine block to somewhere on the body, preferably on the firewall.. clean off the paint and bolt it on with a star washer.... if you do what I typed earlier you can find out where the voltage loss is...either on the power side, or the ground side.. Bobo

Well I bought some shims for the starter, tried a .064, then added a .032, then another .032, no help so I pulled them all and put in a .016. Still no diference so I gave up. You can imagine this was quite a bit of work.

I went down to the local GMC dealership and bought an AC Delco starter. I bolted it in, no shims. It starts perfect, quiet, turns the engine over very fast. I couldn't be happier. That'll teach me to buy non-OEM parts I guess, rememeber that this was the second non-OEM starter in a row with this problem.

There where plenty of signs of metal dust in there, but the teeth on the flywheel where in very good shape. However the teeth on the starter wern't happy, pretty chewed up. When I had the starter all the way out (I'd never disconnected the wires when I was putting in the shims) I held it up and shook it and you could hear something clunking around in there. How nice. I shook the new OEM one and no clunking or noise of any kind.

So then I went after the voltage problems. Found a fairly large voltage difference between the alternator and the battery and an even larger one between the battery and the cab. I located an old crimp connector on each of those wires where the positive had shorted while it was running years ago and both cable's fusable links and blown. I replaced those two old crimp connectors with soldered joints and covered them with heat shrink tubing. No more voltage drop. My windows go up and down at full speed again, yah!

Once again thanks for the help everyone!

I think I'm going to order a replacement positive battery cable for it so I have the fusible links back, but that cable is $80 so it's going to have to wait for a while. -James

James, Instead of the fuse links why not use a large fuse holder like the new vehicles use. I replaced all the fusible links on my wifes Blazer with fuses, makes it easier to check systems and isolate problems. On the starter it sounds like the replacements were set up with the wrong pinion gear.

I've thought about replacing the fuseable links with fuses, however I have no idea what size of fuse I'd need. Seems to be they'd have to but quite large (100amps) and I'm not sure where I'd get such a thing. Digikey maybe. -James