Charging Problem

Riddell · October 24, 2003

I own a 2000 GMC Sierra 1500 4.8L w/ 60,000 KM. I just notice yesterday, as I was driving down a country road, that my headlights were dimming? Then this morning i could here my heater fan slowing down, and my battery gauge would fall from just over half (Normal) to below that and back up again and down??? Is this my altenator failing??

any information is greatly appreciated!!

Ben · October 25, 2003

Most likely IN-FAMOUS GM side post battery issue. Kills batteries, alternators, cables, starters and wacky electronics.

Posted many, many times on other forums and even here.

Std reply below

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YUP!!!!

What you have is the IN-FAMOUS general motors postitive cable/battery problem.

Comes from that lead washer between the two lugs. It's one time use thing and should be replaced whenever the batt positive connection is loosened. If not, it crushes and allows the bolt to go too far into the connection to crack the battery case. Then it allows the connection to become intermittant to kill the alternator. Then it wicks acid into the cable and it continues to wick down to the starter and kill the starter.

I've posted many, many, many times and will again.

Here's the text, hot links and pictures:

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....note that the brass nut is drilled out and just acts like washer. There are TWO OEM lugs on the battery terminal, then brass nut, then accessory lug (3 wires, two 50 amp fuse holder, one 30 amp fuse holder) and alarm power wire. Have since gone to store bought that looks very much like this one (it's shown on #1 Son's battery page).

Hot link to the thread on another forum

TEXT from that article:

That bad battery post design can/does kill alternators, batteries, starters, battery cables, and wreck havoc with other electrical circuits.

Think many don't know what Traveler and I are talking about. Here's an example of what is happening and the cause'n affect:

Take the battery positive cable lug and unscrew it from the battery (disconnect it). Manually hold the cable lug to the battery post. Start the vehicle. Now touch, remove, touch, remove the cable lug to and from the battery pos terminal. THAT is EXACTLY what happens when that stupid lead spacer crushes and allows the bolt to bottom into the battery pos post.

The alternator sees the battery, charges (provides oltage/current), then the connection goes away. Voltage at the alternator goes up (maybe several hundred volts, instantly...or almost that fast). Then when the contact is made again, the alternator will see huge load (maybe hundreds of amps, instantly...or almost that fast). This is called load dumping and will kill a good alternator in short order.

Above load dumping will also kill the battery in short order too. Over voltage and over current. Also will have high resistance terminal, meaning voltage drop, meaning current used at that spot. That current usage turns out to be heat...high enough to melt the battery case, which will allow battery acid to leak into the joint *AND* down the cable (cable acting like a wick and cable insulation acting like a hose...carrying battery acid down to the starter...starter don't like battery acid).

Another cause is that there is a lead spacer between the two cable lugs on the battery post. One time use, as 2nd time tightening the bolt will have the lead washer too short to provide resistance and allows the bolt to bottom out inside the batt pos terminal. That then cracks the batt case, allowing acid to leak...ditto above, ruining cable, starter, alternator, battery, etc. Throwing away the lead washer, cutting off the plastic from the lug blades (flat part only) and replacing the washer with stack of brass washers that won't allow the bolt to bottom is a fix.

All of the above then has this affect on the vehicle computer: turns it on and off. Or various components of the vehicle. Which one??? Who knows and not always the same one. Engine dies for no apparent reason. Doors lock and unlock for no reason. Window motors burn up for no reason. Lights turn on, off for no reason. After market alarms turn on/off and lose their programing. ETC, ETC, ETC.

Another way to avoid/manage the lead crush washer is to use a hardened brass bolt that is threaded whole length, that is longer than needed and a hardened brass nut. Put nut on and screw it to the bolt head. Stack up all of the lugs on the bolt, then screw the bolt into the battery pos terminal till it hits bottom, back off 1/2 turn. Now turn the nut down onto the stack of lugs while holding the bolt hex from turning (do not allow bolt to bottom into the batt terminal and only HAND tight). Tighten the nut till it's tight and makes good connection. This way you'll be able to keep that lead spacer and not have to cut off the plastic covers on the lug blades...

This avoids bottoming the bolt, which is one cause of acid leaks (cracks battery case), other is high resistance and the heat generated melting the batt case...causing acid leak.

Another potential is jumping another car while your engine is running. Here is hot link to that thread at hot link below.

HOW2 jump start without killing your alternator

Riddell · October 25, 2003

thanks for the info Ben!!

asepgrad98 · October 25, 2003

check the terminals for tightness, leaking ofcourse. I bet the problem is the alternator.

Voltage at the alternator goes up (maybe several hundred volts, instantly...or almost that fast)

no way that could be true. If your voltage went up 30 times normal values almost every fuse in the truck would pop at once.

Ben · October 25, 2003

no way that could be true. If your voltage went up 30 times normal values almost every fuse in the truck would pop at once.

then explain how your ignition goes from zero volts to over 30,000 volts in 2 nano seconds?

That is how fast most automotive ignition coils switch from zero to over 30KV.

Now think about this...when you slide across a seat and get zapped touching something, that is well over 30KV and that took very little time to boot.

PS...fuses don't blow from voltage, but from current (amps). Voltage plays, but the actual mechanisim is current melting the fusable link material.

Tree_Hugger · October 27, 2003

no way that could be true. If your voltage went up 30 times normal values almost every fuse in the truck would pop at once.

then explain how your ignition goes from zero volts to over 30,000 volts in 2 nano seconds?

That is how fast most automotive ignition coils switch from zero to over 30KV.

Now think about this...when you slide across a seat and get zapped touching something, that is well over 30KV and that took very little time to boot.

PS...fuses don't blow from voltage, but from current (amps). Voltage plays, but the actual mechanisim is current melting the fusable link material.

Because your ignition coil is a step-up transformer....

I don't think he's arguing about a rate of rise in voltage, just pointing out that your alternator cannot produce a voltage of hundreds of volts.

And if it did, the fuses would indeed blow in milliseconds, as a result of the amperage driven by such a high voltage.....

There may well be a problem with the side terminal battery, but your theories on what precisely is going wrong are incorrect in detail and physics...

The fix you suggest is a good one.

BlackSilver · October 27, 2003

Voltage at the alternator goes up (maybe several hundred volts, instantly...or almost that fast)

no way that could be true. If your voltage went up 30 times normal values almost every fuse in the truck would pop at once.

I don't know if it rises that dramatically, but if you have an open circuit to the battery (like if you remove the battery connection with the engine running) there is a SIGNIFICANT rise in the voltage output of the alternator and all sorts of nasties will happen. Fried computers, blown ignition modules, deaf radios, etc., all can happen in the milliseconds before fuses blow.

Riddell · October 27, 2003

Well, Since the day i posted my question, it has not done what i explained? I checked all the terminals (Very clean + no leakage) their tight aswell.... but i do hear like a whine coming from the alternator, is it possible that it is the alternator going????

Ben · October 27, 2003

I'd bet a Costco Dog lunch that your alternator is going bad....

Don't have the time nor patience to write up Alternator & Load dumping 101, so for those who still don't believe that there is such a thing, or that the voltage goes up way high, just do a search on your favorite search engine and use these search criteria: +alternator +"load dump"

You'll find tons of independent sites that disscuss and address with fixes, including products. Mostly MOV type of shuting devices.

PS...alternator going bad will cause load dumping onto the battery, which will potentially cause the postive connection to get worse and go into this cycle again...

PPS....even though the connection seems tight, clean and no acid, it can still be bad if both the original battery with ruined pos post and/or the lead slug is reused. Cycle through this ruining alternator, cable, battery, starter and other electronics.