Author Topic: Electrical problems  (Read 12080 times)

Offline doctrdoo

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Electrical problems
« on: October 18, 2008, 10:16:42 PM »
I'm having some electrical issues with my 85 C10 pickup and I'm asking the wealth of knowledge here for some help and/or suggestions. I have a 85 C10 pickup ,350 eng w/ auto trans. Here's my problem- I keep having to jump start my truck every morning to get it started. I know the battery is only 4 months old and I just bought and installed a new alternator(78 amp),I have inspected and cleaned the connections such as both battery cables. I have checked the voltage on both the battery and the alternator(small wire in back) when the truck is running-both are at 16 volts.now - if i turn the lights on and the defroster on- the ammeter gauge in the instrument cluster says the voltage drops down to below 13(around 10)and when i turn everything off- the gauge sometimes goes back up to 13 but it never goes past 13 no matter what rpm the engine is at.Sometimes it will drop to almost 8 then come up to 13.I'll let it idle then turn the truck off but when I go to start it back up- it acts like the battery is dead. This all started after i installed a cheap (65 watt)radio.Before I installed the radio- the ammeter would go past 13 with nothing turned on and the rpms up and the truck started every time(no matter how many times I started it).Since this issue has popped up i have disconnected the wires to the radio but the issues still exist.Any help with this would be great-I am at my end with this. Thank you.

Offline choptop

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Re: Electrical problems
« Reply #1 on: October 19, 2008, 07:39:00 AM »
Several things come to mind here. First thing, your alternator output and battery voltage should not be 16volts...ever. Nominal output for a 12 v system should be 14 volts max, anything over this will cook your battery, which is why I think your battery keeps dying. The high voltage can be caused by a faulty alternator ( which can also drain the battery) and the fact that the charge goes down with light loads tells me that you need to look at the wire from the alternator to the battery closely. just because it is connected doesnt mean it is "electrically connected" so check it for corrosion. Look ecpesially where the wire is connected to the connector. This gets corroded from the inside, and isnt as easy to see. If all is well, you need an alternator, especially if the voltage output stays at 16v.  Also check the acid in your battery. I'll just about bet its low from the overcharging. Hope this  helps.
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Offline VileZambonie

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Re: Electrical problems
« Reply #2 on: October 19, 2008, 07:54:19 AM »
Did you hook your radio up correctly? Disconnect it and see if the battery is drawn down in the morning. 16V is way overcharging.
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Offline doctrdoo

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Re: Electrical problems
« Reply #3 on: October 22, 2008, 04:58:41 PM »
Thanks too everyone who wrote with suggestions. The problem ended up being the battery(that was only 3 months old) had a bad cell. When I was checking everything with a volt meter I was looking at the wrong line-the volts were actually 14 volts- not 16 volts.Also- I figured it out that the battery was the culprit by disconnecting the positive battery cable while while the truck was running and checking the output of the alternator with a voltmeter.End result was that I ended up buying a new alternator,battery cables and the store gave me a free replacement on the battery.Everything is good for now. Sorry I didn't write with a reply sooner but I have been running like a humming bird on caffeine finishing everything on the wife to-do list since I came back 6 weeks ago from my 1 year vacation to the land of sand that the military was nice enough to send me on. And "no" I'm not bitter about it-everyone has to do their part and I'm proud I did mine.Thanks again for all the suggestions and help from this site.

Offline ccz145a

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Re: Electrical problems
« Reply #4 on: October 22, 2008, 05:03:29 PM »
Thank you for your service. Glad you figured it out.

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Offline VileZambonie

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Re: Electrical problems
« Reply #5 on: October 22, 2008, 05:41:02 PM »
That is a huge no no. Glad you figured it out but disconnecting the battery while the engine is running will wreak havoc in many of your electrical devices.
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Offline doctrdoo

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Re: Electrical problems part 2
« Reply #6 on: October 28, 2008, 06:00:54 PM »
well- the electrical gremlins have showed up again in my truck. the radio has been disconnected since the first time( so i know that is not the culprit).my battery is still draining somewhere. how would i track this down?any suggestions would be great Thank you.

Offline doctrdoo

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Re: Electrical problems part 2 HELP
« Reply #7 on: October 28, 2008, 08:27:44 PM »
well- I have checked everything that I can think of-the alternator is putting out 12 volts at the little wire, the battery is at 12 volts, i cleaned up the contacts at the fusable link on the firewall and all of the grounds that go to the motor and battery.could it be the starter, the starter solenoid or one of the wires that go to the starter?I really need help with this problem since this is a daily driver.

Offline choptop

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Re: Electrical problems
« Reply #8 on: October 28, 2008, 11:32:54 PM »
The alternator should be putting out between 13-14 volts when the engine is running.Quick check= check the voltage at the battery with the engine off, then start unit and recheck at the battery. It should increase Check the output at the alternator, it will be the larger wire bolted to the alternator. The voltage at the alternator wire and the battey should be the same, If not there is a problem there. As far as checking for a drain on the system, I have an ammeter that I put inline between the positive on the battery and the cable. Then I start unplugging things until the amp drain drop off. I'd disconnect the alternator first. I dont think it could be a starter or starter rely, but it is possible. I've seen stranger things happen. If you are only getting 12volts output when running, that is too low. Idle the engine up and see if it increases. Also make note of your belt. If the alternator belt is loose, it wont charge properly, and they dont always squeel when loose. As stated earlier, dont disconnect the battery cable when running, it can cause all kinds of havoc, and just reconnecting the cable when running can cause the voltage to spike and wipe out the regulator in the alternator. When checking the voltage after starting the engine, the voltage may not jump up to 13 volts, it wll gradually come up after running a few minutes. I know the battery is new and the alternator is new, but I have changed many new parts that failedwhen they shouldnt have. This is particularly true with rebuilt parts. I will spend the extra money to buy new electrical parts, because I have been bit by rebuilt parts to many times. Good luck, keep us updated.
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85 C10, 85 K10, 85 K20,86 C10,86 K10 (all extended cabs)
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Offline doctrdoo

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Re: Electrical problems
« Reply #9 on: November 03, 2008, 03:12:21 PM »
Well hopefully the electrical gremlins are gone. I ended up replacing all the belts and replacing all the electrical connections.I also reset the timing-just to be sure.My ammeter shows that the alternator is charging at 14 volts.I just wanted to thank everyone here for their help and suggestions.