charging and starting

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Oct 4, 2014 | 09:40 PM

jle70

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Joined: Oct 2003

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From: Sullivan, IL USA

charging and starting

For past few years, off and on, I have issue with truck not wanting to turn over.

Example, the other day started fine, shut off 20 min later, dead. Not battery juice.
Swapped driver side with known good battery, starts up, drives home. Next day, dead, even with charger on the whole night. So, the following are my thoughts.
1. Bad positive cable.
2. Bad cable from alternator to relay.
I ruled out batteries, they both checked fine.
I am getting alternator checked tomorrow, but gauge shows charging.
Also, disconnected batteries cause engine to shutoff, are these engines suppose to run from alternator? Should it stay running with batteries disconnected?
Do these have separate voltage regulators or are they built into alternator?
Thanks.

Oct 4, 2014 | 10:03 PM

oldbird1965

Fleet Owner

Joined: Aug 2004

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From: AZ

A computer, PCM, runs the engine. It has to have juice. Regulators are built into the alternator. I would say a bad cable, could even be a negative cable.

Oct 4, 2014 | 11:21 PM

jle70

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Joined: Oct 2003

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From: Sullivan, IL USA

I am aware of the power requirements. I just didn't know if my 95 was new enough to run from alternator, like my 2007 expedition.

I will check grounds, visually they look OK. I need to find resistance limit.

Oct 5, 2014 | 06:42 AM

helifixer

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From: Chino Valley, Arizona

you say dead! are the batteries "dead"? did you check them with a volt meter? or are you saying dead because it won't start?
the relay on the passenger fender will cause an intermittent no start.
have you cleaned the battery terminals?

Oct 5, 2014 | 04:27 PM

jle70

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From: Sullivan, IL USA

Dead meaning, no juice to start, but batteries are OK. I connected them to charger over night and still no power to start.
Yes, thoroughly cleaned all connections.

Oct 5, 2014 | 06:49 PM

madpogue

Lead Driver

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From: Madison, WI

All engines run from the alternator/generator. They START from the battery/batteries. Disconnecting the batteries while the engine is running is a good way to fry the electronics on any vehicle. You can test at least whether the alternator is working with a $10 multimeter. That said, if it doesn't run with the batteries disconnected, the alternator is inop. Does the charging system failure warning light (battery icon) come on when you turn the key to RUN?

Oct 6, 2014 | 12:07 AM

helifixer

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From: Chino Valley, Arizona

Quote:

Originally Posted by jle70

Dead meaning, no juice to start, but batteries are OK. I connected them to charger over night and still no power to start.
Yes, thoroughly cleaned all connections.

change the relay on the fender!
if you want to test it set the parking brake make sure it is in neutral and jump the 2 large post with a screwdriver if it starts the relay is bad. I have changed several of them in the last few years.