91 CTD

Checked all the grounds, I think. seem to be ok

Just like the other guy, all lights pulsate no matter how long it's been running for.

Alt is putting out at idle 14.76 - 15.99 volts Pulsating

Battery isolated with key off, has constant 13.76 volts

Is the regulator internal with alt?

Help

Rich

 

The regulator is external. In '91 some were a separate regulator mounted on the firewall slightly left of center. Later trucks have a computer and the regulator function is one of the things it does. It could also be a bad diode. Have you measured the amount of AC coming out of the alternator?

 

No I have not, is that something I can do at home? Or do I need to take it to a shop?

Rich

 

Is this a major pulsation or a relatively light pulsation at idle and low speeds? My truck does this a idle but once the RPMs come up, I cannot detect it. I have heard this is attributable to the idler pulley bouncing. I have a new alternator and regulator on mine and it didn't change it any. Leads me to believe the idler pulley could be the cause.

Carl

 

If you have a voltmeter that measures AC you can check it. Should be less than a volt. Any more than that indicates a bad diode.