Voltage issue

[Jerryl]

So, what do you think?
Reading form scan tool;
New battery (ACDelco), alternator (93A) with 1500 miles on it.

Idle in Park 825 RPM ~ 13.5 - 13.9 V
Idle in Drive 775 RPM ~ 12.9 - 13.1 V
Ilde in Drive Coolant fans on – 12.5 V
Idle in Drive, coolant fan and lights on ~ 11.6 - 12.2V
Highway cruising 2000 RPM– Lights, blower fan, radio, coolant fan on ~ 13.5 V

Need an Over Drive alternator pulley or not worry about it?

 

[Squid4life]

Maybe get a new 120 amp alternator? You have dual fans right? Maybe you need a higher output alt.

 

[Lee Thompson]

run it

That is the exact same way my 85 setup would read. I even went to 140 amp alt and a double belt pully as I thought maybe it was slipping--no change and it never really gave me any prooblems runnig the # you are seeing. I just always thought it should read higher. Close the hood and don't look at the gage.

 

[6SENSE]

Jerryl, like Lee said, its fine. Remember your reading from a scantool, [probably] reading off of ALDL. From my experience those #s are great. I bet if you take a voltmeter and check readings at battery and at alternator your getting 14v+

 

[Jerryl]

Thanks all.
There is in fact a voltage drop from alternator to ECM of about 0.5 V.
I can modifiy the alternator pulley or ........ found a place that sells a slightly smaller one. Meanwhile ... " I am not looking back".