alternator problem ?

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Jul 21, 2004 | 05:09 PM

firebug

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Senior User

Joined: Jan 2003

Posts: 156

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From: East Texas

alternator problem ?

When I start my truck 95 PSD, it starts fine and idles fine ,but the amp gauge in the dash shows aprrox 8-10 amps. When I start driving at approx 20 mph the gauge jumps

up to 12-14 amps and stays there. At night you can see the headlights go from dim to normal when the gauge jumps. The guy I bought the truck from says the alt was replaced approx 9-10 months ago. Any ideas or is this normal for a PSD

Jul 21, 2004 | 06:29 PM

2001_73_PSD

Freshman User

Joined: Jun 2004

Posts: 35

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From: Minnesota

It sounds normal to me... the gauge measures volts and it sound like it is getting the appropriate voltage between 12-14 ... usually 13.4v ... when the truck is idling the alternator isn't producing as much voltage which is why you get the dim headlights and lower voltage reading and that is normal... but what concerns me is the 8-10 that you mentioned... if you have a volt-ohm meter I would measure the actual voltage at idle.. it should be closer to 12v... possibly the battery/s

Jul 21, 2004 | 06:58 PM

Rancha9

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Joined: Jul 2002

Posts: 665

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From: Kingsland, GA

Unles you are pulling near the alternator's maximum load, you should NOT have a large voltage difference between idle and running. You need to go get that alternator tested and replaced, as some of your engine control systems and sensors can read incorrectly or even damaged if run on the wrong voltage.

Jul 21, 2004 | 07:09 PM

slc10844

Posting Guru

Joined: Oct 2003

Posts: 1,332

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From: Baltimore

Check the belt tension and make sure the electrical connections, including the battery, are clean and tight.

Jul 21, 2004 | 09:22 PM

tjbeggs

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Joined: Apr 2004

Posts: 12,835

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From: Silver Lake Dunes, MI

ok here's the skinny on the voltmeter jumps. i am not sure which years this covers but my 95 is the same way. its the way it designed to work. if you start your truck the computer will not command the alt. to charge for a fixed amount of time. 30 or 40 seconds round about. i will bet that if you time the jump from start up it will be the same everytime. not sure why ford made it that way but it is. i hope that solves you mystery.

tjbeggs

Jul 21, 2004 | 09:46 PM

Bluesbandit

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Joined: Mar 2004

Posts: 152

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From: Central Texas

My 97 does this at every start up after glow plugs have been allowed to warm up. You can even see hear the difference in fan speed if the the a/c is on. My theory is glow plugs, turning the engine, ect, draw down the batts. Votmeter gauge reads voltage not amperage, and it takes a few seconds to get everything charged up after start up. Just a theory though. From what I've read it's normal and you shouldn't have any worries if that is all that pops up.