'96 5.7L alternator trouble; need some advice

[semperfi]

Hey guys, My '96 Chevy Z71 w/5.7l is having alternator problems. The head lights & cluster lights "pulsate" when turned on. I was told that the rectifier is probably bad. I was told that I could check for AC volts across the battery terminal with voltmeter when the engine was running & if it showed any ACV, then one or more of the diodes are bad allowing AC current to "leak" or flow. Is this correct? This being said, I currently have the 105 amp alternator w/internal fan on the truck. Can I "update" the replacement with a 140 AMP that has the external fan? will this bolt, plug & play without any mods?

 

[michael hurd]

Chances are that a new alternator will not solve your pulsation issue. If you feel inclined you can pull it off and have it tested at a parts store. They will be able to tell you if there is leakage through the diodes and how much. You can replace that alternator with a higher output unit with the correct belt.

 

[SAATR]

Changing it for the external fan will require some mods, the wiring harness at the very least. Swap your for an AD244 alternator from an 04 2500HD gas burner. It's the 140A option for those trucks, and will bolt and plug right in. You just need a slightly longer belt.

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[semperfi]

Chances are that a new alternator will not solve your pulsation issue. If you feel inclined you can pull it off and have it tested at a parts store. They will be able to tell you if there is leakage through the diodes and how much. You can replace that alternator with a higher output unit with the correct belt.

@ Michael....why do you say that changing the alternator will not fix the pulsating lights? What else would be causing this beside a bad rectifier?

 

[semperfi]

Changing it for the external fan will require some mods, the wiring harness at the very least. Swap your for an AD244 alternator from an 04 2500HD gas burner. It's the 140A option for those trucks, and will bolt and plug right in. You just need a slightly longer belt.

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@SAATR....what engine is this? 6.0l? when I check this at Advanced Auto it shows a 4 pin connector. My '96 has a 1 pin conn.

 

[SAATR]

What do you mean one pin? Should have a 4 pin oval connector, even if only one of them has a wire in it it's considered 4 pin.

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[semperfi]

What do you mean one pin? Should have a 4 pin oval connector, even if only one of them has a wire in it it's considered 4 pin.

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@SAATR.....OK, yes, it's a 4 position connector with only (1) wire/pin in the connector. What about the engine size. I need that to be able to look up the part on line.

 

[SAATR]

It would be a 6.0L, yes.

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[michael hurd]

Google search fluctuating voltage gm truck and you will get a number of results, I know that at least on the newer trucks they had a bulletin on addind a harness to correct it. The factory omitted external voltage sensing and high loads especially at idle will cause the voltage to fluctuate.