Alternator

[SAndreasen]

My alternator is only giving 13.5 volts and it takes a few minutes before it gets going grid heaters are not on the gauge doesn’t fluctuate so what else should i check before replacing the alternator? My handy factory service manual on cd no longer works

 

[fest3er]

If nothing else is drawing significant current, it probably has a weak or failing diode.

If you know someone with an oscilloscope, connect it and observe the output of the alternator. IIRC, alternators are usually '3 phase'; a bad diode will appear on the scope as a flat or 'low amplitude' semi-cycle.

 

[Bill Lins]

If it's a Denso, it's much cheaper to just replace the diode bridge & brushes. You don't have to split the cases- everything's under the rear sheetmetal cover.

 

[Seabee]

Could it just be the "regulator?" I know that the "regulator" on our trucks is usually good or completely bad, but.............

 

[petersonj]

@SAndreasen, if this is on your '98 24 valve, then there may be a battery temperature sensor under the driver's side battery. That temperature sensor is an input to the PCM to help determine what the voltage should be at the alternator output. 13.5 volts is not out of range for a hot day.

- John

 

[SAndreasen]

Hopefully not tbe regulator because it is part of the brain . Todsy voltsge has stayed around 9 or 10 then will creep up to about 13 or 13.5

 

[NIsaacs]

My first alt quit at 295k miles, second one at 329k miles both Napa. They do have a lifetime warranty so keep your invoice. Low voltage will cause all kinds of headaches so fix it asap.

 

[Bill Lins]

Hopefully not tbe regulator because it is part of the brain . Todsy voltsge has stayed around 9 or 10 then will creep up to about 13 or 13.5

If it is, Motor City Reman has the one that mounts inside the back cover of the alternator for a very reasonable price. Easy to connect & bypass the the OEM one.

 

[SAndreasen]

If it is, Motor City Reman has the one that mounts inside the back cover of the alternator for a very reasonable price. Easy to connect & bypass the the OEM one.

I may have to look into that

 

[DownByTheRiver]

https://heielectric.com/shop/alternators/dodge-cummins-one-wire-alternator-1989-2002/

Here's another option that supposedly keeps from frying your ECM. I'm not really sure what it means as far as changing wiring goes, or if you can just use a regular alternator if you get into a bind, but check it out.