Chevy Silverado Electrical Nightmare

Maintenance/Repairs
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1

I have a 2007 Silverado 1500, purchased as “certified” used from a Chevy dealer and now with less than 40,000 miles on the vehicle. It has two major electrical problems.

  1. The truck intermittently loses all electrical power WHILE PARKED, even after being driven for many miles and then stopped for only a few minutes.
    The door must be opened with a key rather than the remote fob and after electrical power is restored, the clock must be reset, etc.

  2. WHILE DRIVING, periodically the engine cuts in and out, the door locks slam up and down, the interior and exterior lights flash on and off, the instrument needles slam to the stops, etc. All these things occur at a rate of about once per second. Sometimes this is all preceded by the airbag indicator light flashing on and off a couple of times, as though the truck just wants to taunt me.

Generally, I’ve been able to get the truck going and to TEMPORARILY stop the other problems by shaking and re-tightening the positive battery cable, but after numerous dealer visits the problems continue to recur.

Twice in the last two years a dealer decided the problems were due to defective batteries and replaced the battery. I was told that all computer codes and electrical connections were checked on each dealer visit. As the problems continued and two dealers were unable to observe or to diagnose the problems, I paid a second dealer to replace the positive battery cable ($200 parts and labor), thinking perhaps the problem was an internal cable short. Again the problems recurred. (I’ve long since started to relate to Shatner / Lithgow in the Twilight Zone “gremlin” episodes.)

After many occasions of tightening the cable clamp on both the original and the replacement AC Delco cables, last week I finally broke the narrow soft metal bolt and had to travel to yet a third dealer to pay $10 for a replacement bolt just to get the truck running for the day.

I now believe the problem might be that the Delco positive cable clamp on my 2007 vehicle is both absurdly designed and extremely cheaply made. The small diameter vertical clamp bolt with the little ears designed to force the clamp around the post is made of cheap, soft metal and seems to lose proper contact with the battery post, even on a brand new battery, perhaps as a result of heat expansion / contraction and/or vibration.
Compare this style clamp to a traditional, simple clamp with a larger diameter horizontal bolt that DIRECTLY and very strongly closes the clamp on the battery post.

In researching this on the internet, I’ve found many other complaints of similar problems by other owners of GM vehicles. Surely GM must be aware of this issue.

I’d be very interested to know whether 2008-2011 Silverados and other GM vehicles have positive battery cable clamps with the same design (Rube Goldberg clamping to post by small vertical bolt that forces clamp over little soft metal ears) or if at some point the positive cable clamp has been changed to something different, perhaps the original style clamp that worked effectively on all brands of vehicles for the previous several decades?

I’m going to try to find a cable or at least a traditional style proper clamp (for the dual cable) to replace the Delco part as an experiment. However, if anyone, unlike my local dealers, has a better theory for why my Silverado has been unreliable, infuriating, and sometimes unsafe to drive for the last two years I’d like to hear it.

I emailed Chevrolet about this problem and received a return call from a non-technical person at a call center in another country, who basically told me to take my now out-of-warranty vehicle back to a dealer for yet another visit. At this point, that was not a response I found helpful.

Now, for what may be the final insult, the truck has started occasionally and also randomly loudly “thunking” while smoothly accelerating in driving around town. Of course, I’ll get the truck up on a lift to check U-joints, lubrication, etc., but I can’t help but wonder if the engine cutting on and off has damaged the drive train. If so, now that the warranty has expired, that should be a delight for my credit card!

2

Your Twilight Zone comment was good. Lets see if we can get you back to the ‘normal zone’.

First off, a lot of people make a mistake when they overtighten battery clamps. It makes problems rather than solve them. They should be snug enough so they don’t twist and that is it.

From what you have stated I think you are close to the trouble and it should be pretty easy to find. I suspect the trouble may be with the connection between the battery and power distribution panel under the hood or in the panel inself. You could try moving suspected trouble areas around while monitoring the power to the panel using a test light probe. Using a screwdriver handle to tap on things with may help locate the trouble faster. Check the chassis ground lead also.

3

Thanks very much for the reply. I’ll follow up on your advice. And yes, absolutely right about tightening battery clamps. In my case, I was sort of led down a path toward over-tightening and eventually breaking the pitiful little vertical bolt after many occasions of power loss and after the positive cable was replaced by a dealer and the problems began again before I made any additional adjustment or tightening.

In researching this I’ve found many, many, people with similar and even more bizarre electrical problems on GM vehicles. Of course, all brands of vehicles have problems, but there is definitely a pattern indicating some very poor quality control, if not design, at GM and especially AC Delco. The only other person I know well who has a GM vehicle (Avalanche) has also had a long and infuriating history with electrical / electronic problems.

This was my first GM vehicle in over 20 years and it will probably be the last in my lifetime. My truck developed some additional, probably unrelated, problems yesterday. I just hope I can get the various problems solved to the extent that I won’t feel like a heel when I trade this truck for a non-GM product. That will be a happy day!

4

“Just tight enough that they don’t twist” is exactly right cougar. Of course having a clean cable end and battery post is necessary.

5

Again, just for the record, the present positive cable on my truck’s battery post (entirely clean with both new cable and a new battery) was dealer installed and presumably “just tight enough so that it didn’t twist.” Still the electrical power failed repeatedly and could be immediately, if temporarily, restored BY TIGHTENING THE CLAMP.

And by the way, at the time these problems began in earnest the first person to suggest that the clamp was too loose and should be tightened was the dealer’s service manager while I was talking to him on the phone. He might still remember the horn blasting over the phone after I followed up with a 10mm wrench in one hand and the phone in the other.

However, long story short, yesterday for the very first time the truck’s power shorted out and then recovered all by itself while sitting in my driveway. I know this because when I got in the truck it started but the clock showed 1200 when it was about 230.
This makes me now think that the problem is not in the cable but elsewhere, and I’ll be following up on Cougar’s suggestions as well as ideas I’ve heard on gminsidenews.com and elsewhere.

In any event, I wonder if anyone can tell me, or even offer a good possibility, as to why the design of the clamp was ever changed from the traditional, reliable, simple, horizontal bolt to close a horizontal clamp to this Rube Goldberg apparatus having a small vertical bolt and a flat base with, as the dealer’s parts man put it, “two tits and a stud on it.” (For greatest accuracy, employ a Slim Pickens voice when you say those words.)

Was there really some functional reason for this design?
What was the motivation for the change?
What was actually accomplished, beyond a greater likelihood of failure?

6

If twisting at the cable end often results in restoring current the problem may be the crimped connection at the cable end.

7

Like a lot of things that get changed from the old reliable method or design the new piece is most likely cheaper to produce and so it makes more profit for the company.

I assume the battery that was changed out was the large main cable that ties to the starter and has the battery clamp on it. The cable that needs to be checked is the smaller one that ties to the power distribution panel under the hood along with the chassis ground lead from the battery.

8

Also, if not mentioned already, there are often 2 positive cables with the cable ends stacked and a spacer between them. The plastic insulation and the spacer often get out of line and cause poor contact.

9

After reading the post I am leaning towards a door lock and anti theft combo problem.

10

The cable(s) changed included both the larger and smaller cables on the positive side. Same problems before and after the cable change. So except for the fact that tightening the nut on the vertical bolt (nothing else moves) always restored power until I finally broke the little bolt on the second clamp, my theory about the problem being bad design and quality of the clamp would certainly be refuted. And of course I know that there are surely many other owners who have had no problems with this clamp apparatus. Maybe my truck needs an exorcist or a visit from Deepak Chopra?

Door lock /anti-theft problem? That’s an interesting new idea! Certainly every time I’ve been standing over the battery when the power comes back, the alarm/horn starts blasting in my face until I can fish the key fob out of my pocket. I thought this was just one more perk of owning a Chevrolet. I’ll say one thing, the Silverado has a great horn!
But could a short somewhere in the door lock or anti-theft circuitry cause all the problems I’ve been having? I guess it’s possible, now that I think about it.

I definitely agree with the cheaper component / more profit theory, Cougar. In this case, though, I wonder how much cheaper a new design of a more complex apparatus could be, even if it’s made by Chinese workers who mold pot metal for 9 cents a day? And if the component does cause reliability problems and dissatisfied customers, what sort of economy is that? Of course, every one of us has opinions, informed or not so much, about this sort of thing vis a vis the U.S. auto industry…

I had to fly out of town and will not be able to pursue the truck problems until next week. As I have neither the time nor a lift, I’ll be pasting and copying all the good suggestions received here and elsewhere and taking the truck back to a dealer next week with all of those ideas highlighted and a request to keep the truck until they can sort it out. I’ll post whatever the result turns out to be.

Thanks for everyone’s feedback.

11

Also, when I get back to the truck’s location, I’ll check both new new and old cable assemblies for the insulation and spacer set up between the two cables near the clamp.
That bit is hidden under the big red plastic cover, which also holds the little vertical bolt in place.

Thanks.

12

It sounds as though you are completely losing batt power to the entire vehicle periodically. This SHOULD be rather easy to figure out. YOu need to go thru ALL of your electrical connections. At the batt, at the fuse block under the hood…at the alternator… AND DONT FORGET YOUR GROUND WIRES…

A faulty or loose ground will do this to you in one fell swoop. Make sure your batt cables are cleaned and greased and tightened. Same goes for any grounds… Also look for any broken wires… This will probably be easy to sort thru with some patience.

13

I have the same issue.I have a 2007 Silverado WT no power locks or any thing. I replaced the battery and both positive and negative cables with OEM cables from AC Delco. After replacing the battery I went a full month before the issue started again. It is as if the battery is completely disconnected. If I pop the hood and bump the battery with my fist power is restored. Two batteries and all new cables. WTF is going on?

14

Have you checked your ground connection from battery to body?

15

I checked both the ground to body and ground to block when i replaced the OEM cables

16

Does this model have a junction terminal? If so, that could be the problem. It is usually located close to the battery positive terminal and will have a small cover over it.
The battery positive terminal will have 2 cables. One the main cable to the starter motor and a smaller cable routed to the junction terminal. If it has this, try cleaning the termnal and cable ends.

All electrical power except the starter motor windings go through that junction terminal and they can cause fine one minute, faulty the next symptoms.

1 Like
17

Is that the terminal with the big flat fuse in it? If i will try cleaning it tomorrow, also thinking of running an additional ground to the chassis. Since the battery is a side post and top post can I run the additional ground off the unused battery post?

18

Another idea, run a pair of wires from the engine compartment to the cab. Then connect the side in the engine compartment to a place in the main power circuit that should be powered up when the key is in on. And monitor that voltage with a volt meter (DVM) placed where you can see it while you drive. You can move the take off point around from day to day, hopefully it will fail and you’ll have discovered a good clue to the cause.

19

Which 2007 Silverado do you have?

Classic body style . . . kind of rounded

Or the new body style . . . more angular

Classic body style has side-post battery group 78

new body style has top post battery group 48

20

2007 New body style. Uses battery group H6 Top Post. This particular battery has both top and side posts, as did my last one.