Group 78 Battery Connector Issues

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4,400
Location
Kuwait
Thread starter
Weird bit of a problem on the '05 GMC Envoy yesterday. Turned the key to fire up, and I usually wait until the fuel pump primes before cranking. Soon as I cranked, all the electrics died - dome lights, instrument cluster, audio head unit. I couldn't even turn the key back to the lock position. The Motorcraft branded (BXT-78E) East Penn I got is only 2 years old. Popped the hood, checked battery voltage and it was 12.6 V, load test dropped that down to 10.1 V. But as soon as I touched the battery connectors, the lights came back on. The truck wouldn't start, and everything died again, but I had an 8 mm wrench on me, so I went ahead and tightened the bolts and it fired right up. Does this mean I just need to sand the contacts and replace the bolts (I have a couple in the box), or is this something else? Thanks!
 
Messages
2,597
Location
San Rafael, CA
I've owned many GM trucks with side post batteries and have changed batteries, ignition switches, and starters, just to find out the problem is bad terminals. Even if it looks ok from the outside taking the bolt and terminal out and inspecting and cleaning everything will probably fix your Envoy.
 
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9,983
Location
Waco, TX
Originally Posted by Falcon_LS
Does this mean I just need to sand the contacts and replace the bolts (I have a couple in the box), or is this something else? Thanks!
Yes, that's all you need to do! It's a pretty common problem on side terminal battery connections.
 
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35,760
Location
ME
Wiggle the side terminals OUT of the rubber. You may find corrosion that you can clean up. You want the back side as well as the front side of the cable to be clean. You only get half of it if you don't wiggle the little bolt out. You can also get a 3/8-16 by 1" bolt, nut, and lock washer to replace the cheezy GM bolt. Assemble the nut and washer up by the head, run this in like a stud, then run the nut down so it compresses the lock washer against the cable. Permanent springiness, it digs in better.
 
Messages
1,845
Location
missouri
It seems battery manufacturers have lost the ability to make acid tight connection between the terminal lead and the case plastic. They could do it 20 years ago, but evidently not now. If the battery is leaking I replace it. Cost reductions rise again. I bet a federal law that the battery company has to repair all the damage their leaking battery causes would fix this right way. On side terminal I remove and clean the bolt, or replace it, they are pretty inexpensive. I clean both sides of the terminal and baking soda them. Where the mold on the plastic, acid can get in there and ruin the connection and not be visible unless you look close. You may need to replace the cable. Then everything, bolt, both sides of battery connection, and battery post, not the inside of the threads though get coated in sticky grease. Then I make up the connection, dress remove excess grease and never seem to have problems, unless the crap battery decides to leak again. Rod
 
Messages
1,015
Location
Minnesota
I first ran into the side terminals with our new '72 Vega and it was fine, but yes GM was having more recent problems and our '06 Malibu was getting close to the end of using them. I've never had a problem with the terminals or batteries in a number of GM cars in the years between and still have several cars with them.
 
Messages
4,080
Location
Texas
I have had corrosion get in / under the plastic . Even to the point of damaging the wire under insulation . I use bicarbonate of soda to neutralize acid , fight the green crusties and clean . Then grease the connections . If the condition is too bad , replace the cables / terminals .
 
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