Mechanics

IS IT MY ALTERNATOR, OR ?

2003 Dodge Caravan • 292,000 miles

Voltage light came on, turned van off, restarted, light stayed off. Next day, light came on again. Tried above, but van wouldn't start. Tried to start again after 5 minutes, van started.
5 minutes after that, abs light, & brake light, came on. I was almost home, so continued driving. As I pulled into parking lot, all the dash lights came on, rpm indicator jumped to 3500, while speedo went to 0 kph.

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Pcgrafix
January 2, 2012.




From the symptoms, it sounds like the charging system is quitting and system voltage is going low. That will make computers do weird things. If you can catch it when the problem is occurring, use an inexpensive digital voltmeter to measure battery voltage while the engine is running. It must be between 13.75 and 14.75 volts. If it is low, a common cause is worn brushes in the alternator. They can be replaced for 20 bucks, but most people just replace the entire alternator. It would be smart to measure the two voltages on the two small wires on the back of it first to be sure that's the problem. One will have full battery voltage only while the engine is running. The other one must have less but not 0 volts. 4 - 11 volts is typical. If you find 0 volts, the brushes are worn.

Caradiodoc
Jan 2, 2012.
I have a similar problem. I have a 2003 Grnd Caravan, 3.3 flex. I was driving on the interstate when my voltage warning light came on and rpm indicator went to 3500 and my radio went off and on and finally off. I could'nt accelerate and I pulled over to the shoulder and stopped my car. I started it up again and got back on the highway and made it to a nearby Wal Mart only traveling in 2nd gear. I bought a battery thinking my battery (which was just past the 2 year mark) was bad and causing problems with the computer. Installed it in the parking lot and made it back to the highway but the voltage warning light came on again and I couldn't get out of 2nd gear. I made it back home but need to find a solution as this is my work vehicle.I have 254,000 miles.

Tiny
Wandrwiz
Oct 4, 2012.
The battery warning light isn't for telling when the battery is defective; it's for when it's not getting recharged while driving. That is usually the fault of the alternator. Typically the brushes wear down and cause an intermittent connection.

You can use an ohm meter to test the brushes. It can be done with a voltmeter too. Measure the continuity between or the voltage on the two smaller terminals on the back of the alternator. Voltages must be read with the engine running, not just with the ignition switch on.

I never replaced the brushes on a 2003 but on my '95 Grand Caravan that can be done without removing the alternator from the engine. I just did that on my '88 Grand Caravan daily driver a few months ago. That was an older, larger style alternator that had to be removed, but the whole job took about a half hour. That nine-dollar part was better than buying a whole rebuilt alternator.

In the future you should start a new question rather than piggybacking on this one. I am the only person who will get an automated e-mail directing me back here, and if I don't know the answer, none of the other experts will even see it or have a chance to help.

The voltages on the two smaller terminals might be different than what's described on that page. Chrysler had a REAL nice voltage regulator circuit since 1970 through at least 2000, then for who-knows-why they decided to turn it around and lose some very simple diagnostic characteristics. Instead of 12 volts and "something less than 12 volts" on those two terminals, I believe you should find 0 volts and "something greater than 0 volts".

Regardless, measure those voltages and holler back. We should be able to make sense of them.

Caradiodoc
Oct 5, 2012.
Thanks. I did send it as a separate question after I figured I should of not tagged it to this one. Thanks so much for your time in answering. I found that when my car was running, my brand new battery voltage read 11.5v. No charge voltage. So it was the alternator. If the PCM and shift solenoids don't get enough juice, then there could be problems with transmission shifts. At least that is what I was told. Sounds logical. Thanks again.
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Tiny
Wandrwiz
Oct 5, 2012.
Usually it's just the brushes that wear out. I recently replaced them on one of my Grand Caravans for nine bucks.

Caradiodoc
Oct 5, 2012.
I replaced the alternator and belt. Works like a champ.

Tiny
Wandrwiz
Oct 8, 2012.

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