Alternator Problems at Idle?

[GoremanX]

Hello,

I'm new to the message board, but I've been a TDP and mailing list member for a long while.

I own a 1998 K2500 Sierra 6.5TD. Ever since I bought it back in May, it's had an issue where the engine stutters when I accelerate slowly from a dead stop. This is especially apparent when driving in reverse, the engine almost wants to stall. Once the RPMs are high enough, the problem disappears and everything runs flawlessly. I've checked the lift pump, changed the fuel filter, and didn't notice anything amiss in the engine bay. There are no weird noises or anything.

Then earlier tonight while idling at a red light, I noticed that the needle for the voltmeter was jerking around slightly, and my headlights were flickering faintly at the same rate as the jerking needle. I don't usually drive at night, so this has probably been going on since I got the truck.

Maybe the low voltage is affecting the engine's operation near idle? The engine RPMs sit just above 500 at idle, which I find kinda low. But this is the first big diesel I've owned, so maybe it's normal. My last few diesels were old VWs. We've put over 10,000 miles on the truck since we bought it in May, and we've never had a battery die, so I assume the alternator is doing its job when the RPMs are high enough.

What's my next step to fixing this problem?

Thanks,
Frank

[DmaxMaverick]

Welcome to the Forums!

You problem sounds more like a connection issue. Actually typical in the "salt belt". The grounds and battery connections are crucial for smooth running and battery health. Try cleaning your battery terminals and all ground points. That's usually all it takes to get your electrical system back to normal. Your symptoms indicate a body ground is the suspect.

Also, these "big Diesels" idle kinda' slow, compared to what you are probably used to. The idle speed is controlled by the PCM, and there is no adjustment. Your idle is fine. The higher RPM's are probably "cleaning up" the weak ground.

[Bnave95]

Does the Tach do the same? D-Max has the ideal and cleaning the Elect. grounds and pos. is a yearly to do list on my truck.

[GoremanX]

I just had a good look under the hood.

I inspected the grounds and cleaned them with sandpaper. It didn't help matters any, although they were definitely due for a cleaning. Then I checked the terminals at the batteries. On the positive terminal of the passenger-side battery, there are two wires. One wire has a gross oxidized copper ring and connects directly to the starter. The other wire has a much cleaner ring and connects to the other battery's positive terminal. The gross copper ring from the starter wire was between the battery and the other wire's ring, preventing a proper link between the two batteries. So I cleaned the nasty copper ring with sandpaper and placed it on the outside of the other ring.

This fixed everything! All the throttle hesitation, the problems reversing, the dead spots in the go-pedal's travel range, everything! Now the truck drives silky smooth and has tons more power from a dead stop. I did a noisy smoke show in front of my evil neighbour's house to celebrate.

Here's a picture to illustrate. This is after I switched the two rings around. Previously, the copper ring was under the other ring.

http://www.projectgmc.com/temp/battery.jpg

I noticed that the voltmeter needle still jumps around a bit when I have a turn indicator flashing. It stutters to the same beat as the flasher. But it doesn't affect the throttle anymore. Is it normal for the needle to sway like that when a flasher is on? I've never noticed it before. Maybe I need a new flasher module?

Thanks,
Frank

[Robyn]

Hello and welcome
In looking at the nice pix you put up I will recommend you toss them cables and get some new ones.
The side terminal cables are POOR at best so they need to be in top shape.
The little bolt on type in the pix that clamp to the cable are notorious for trouble.
Order a new set of factory cables and be rid of these troubles. Do all of the cables as the grounds are terrible about corroding in the end that bolts to the engine.
If you want to take the time and dont mind some work get some good welding cable about 1-0 in size and solder on copper ends and use bolt on top terminal batteries. The little copper terminals are easy to get at most harware stores. Just use rosin core solder and a propane torch to do the ends. shrink tube the joint if you like, I use liquid tape and call it good.
My 94 just got and overhaul and I bought all new factory cables for it and that fixed a buttload of issues.
OH the wiggle in the meter with the blinkers is somewhat normal as long as its not to excess. With all accessories running, lights too you should see 13 volts at least on the meter. 14 at the batteries.

Good luck
Robyn

[NH2112]

Welding cable is THE way to go, no ifs and or buts. It's so flexible you can tie it in knots, and handles so much power you can actually go with a smaller size than stock and still handle everything your electrical system will ever ask for. However, the outer insulation will turn into a gooey mess if (WHEN) oil gets on it. You can cover the cables with split loom (good because welding cable isn't all that resistant to abrasion), or just ensure your engine is kept clean and any oil leaks get tended to promptly. Years back I made a set of battery cables out of T&B battery cable, crimp-on ends, and some THICK heat-shrink tubing, all of which we had in stock at the Hyster shop where I worked at the time. I never had any electrical problems, but the cable was very stiff and almost impossible to work back to the starter. I think pulling the metal fuel line out from behind the alternator and under the intake, without removing the alternator and intake first, would have been easier!

[GoremanX]

wow, I feel REALLY stupid right now... I have no idea what's meant by "welding wire". All the welding wire I've ever seen is bare, and I've never seen welding wire that's thick enough to be a battery cable. I asked the guys at the welding store where I get my BlueShield, acetylene, oxygen and MIG welding wire from, and they have no clue what I'm referring to.

Can someone pretend I'm a small child and explain it to me a different way? I really like the idea of making my own awesome super-conductive battery cables.

Thanks,
Frank

[Robyn]

Welding cable is the heavy black leads that come from the welder to the ground and the stinger.
Most welding shops can help you out.

Robyn

[KallyI]

According to "Arc-Zone.com", a welding cable (not wire):

"Referred to as a current carrying welding cable. Welding cables carry the welding current from the machine to the torch and complete the circuit back to the machine through the work lead cable."

A welding cable must conduct a lot of current, and be functional in a wide range of temperatures, both operating, and ambient, so it must remain flexible in all conditions. The businesses that you were asking about should have known at least that much, but who knows:confused:

Hope that helps a bit.

[GoremanX]

Oh THAT kind of cable!!! Heck, I have tons of that in the garage already! I guess I'll go ahead and make me some custom battery cables just for fun...

Thanks,
Frank

[GoremanX]

I found the cable in the garage. I'm not sure what gauge it is though, the markings on the sleeve are mostly gone. The only markings I can make out are "X5 Powerstart Corporation". The O.D. is 1/2" and the conductor diameter (made up of countless thin copper strands) is 3/8". The cables are as old as the earth... if the earth is about 20 years old. But the sleeve is still in flawless condition and none of the conductor is corroded. This is surprising since these wires have been subjected to a lot of moisture while waiting for me to discover them. Other than the markings being worn off, these wires look brand new! I have about 50' of this stuff in 2 lengths of 25' each. It's VERY flexible. Here's a picture:

http://www.projectgmc.com/temp/battery-cable.jpg

The end being shown here has been exposed to the elements for 20 years. The copper still looks shiny and new. The nice thing is one length has black sleeving (can be used for grounds) and the other has red sleeving (can be used for positive). Makes for a nice visual distinction under the hood.

I cut off a foot-long section to check with my multimeter, and it registered 0 ohm resistance from one end to the other.

Will this serve as my new battery cables?

Thanks,
Frank

[GoremanX]

I did some further "tests" on this cable. I dipped it into some old motor oil that used to be in the 6.5TD. The sleeving was unaffected. I dipped it into some brake fluid, with the same results. I dipped it into raw antifreeze, again with no ill effects. I dipped it into some diesel I had lying around, and the sleeving remained unaffected. Finally, I tried leaving it in isopropyl alcohol for a few minutes. Still nothing bad happened (except the garage smells gross now).

I then proceded to tie a knot in the cable. This is the foot-long length I cut off earlier. The knot wasn't very tight, but I noticed that the cable can be bent into about a 2" loop without any effort. Quite the flexible stuff!

So I took my foot length of cable into the house and placed it on the kitchen counter. After cleaning all the chemicals from it, I said "Make me some coffee!"... but nothing happened. Then I placed a vegetable next to it and said "Please slice and dice this carrot!"... to no avail. The carrot remained whole.

Based on my "tests", this cable does not slice, it does not dice, and it does not make very good (or any) coffee. But it DOES seem to have all the perfect qualities for making outstanding battery cables. Therefore, I'll try and find some good weld-on terminals on Monday and see if I can make myself some awesome battery cables for the Sierra.

Here's a chart to recap my "test" results:

Outside Diameter: 1/2"
Conductor Diameter: 3/8"
Conductor Type: "Countless thin copper strands" TM
Resistance: 0 ohm per foot ** (to be verified)
Flexibility: 2" loop without effort, 1" loop with minimal effort
Motor Oil Dip Test: PASS
Brake Fluid Dip Test: PASS
Antifreeze Dip Test: PASS
Diesel Dip Test: PASS
Coffee Making: FAIL
Vegetable Slicing: FAIL
Vegetable Dicing: FAIL

Thanks for all your input!

Frank

[KallyI]

Bummer that it can't make coffee..:D

Looks like the right stuff!

[rameye]

The flickering at low idle my also be an indicator that one of the diodes have failed inside the alternator. So instead of getting a nice even flow of electrons your seeing the ac pulsation which is particularly noticeable at idle speeds.

This will give you lower voltage along with all the other gremlins that comeout and play during low voltage.

If your cables dont work, then its time for a new alternator. You can get a new one at autozone with a lifetime guarantee for a little over $100. The guarantee is nationwide so you can replace a bad alternator all over the country pretty much. Not worth the price of replacing the diode trio/rectifier @40 bucks plus your labor.

Good luck

[autocrosser]

The cure to you problem is really pretty simple.. Get a brass bolt, a couple of brass washers and nuts. Run the bolt in until it bottoms (don't over tighten as you will damage the battery). Cut the head off and you will have a brass stud that you can put a nut on to fix the stud in the battery and then clean the plastic off the battery terminals and put then on the stud between the washers. Use some pattery anti corrosion on the connections and you shouldn't ever have any more trouble out of them. I have had the set up for 8 years and never had any more problems with the connections. This has been on the forum in the past but I haven't seen it lately.

You problem was caused by the connection isolating the driver side battery from the passenger side. The alternator feeds the drivers side and the truck is fed from the passenger side so it doesn't see the alternator output.

[Bnave95]

The cure to you problem is really pretty simple.. Get a brass bolt, a couple of brass washers and nuts. Run the bolt in until it bottoms (don't over tighten as you will damage the battery). Cut the head off and you will have a brass stud that you can put a nut on to fix the stud in the battery and then clean the plastic off the battery terminals and put then on the stud between the washers. Use some pattery anti corrosion on the connections and you shouldn't ever have any more trouble out of them. I have had the set up for 8 years and never had any more problems with the connections. This has been on the forum in the past but I haven't seen it lately.

You problem was caused by the connection isolating the driver side battery from the passenger side. The alternator feeds the drivers side and the truck is fed from the passenger side so it doesn't see the alternator output.http://www.thedieselpage.com/members/batterm.htm