gen 2 light wont turn on

[87silverado]

gen 2 light wont turn on when i go to start my 09. ive checked the bulb and dash circuit board. also checked all the fuseable links by the junction block on the passenger side and the one by the glow plug relay.

tested voltage at batts with it running. front was batt 14.5 rear batt was 12.7

tested voltage at alts while running. driver 14.7 passenger 27.35

not sure were to go next

 

[doghead]

Measure just the rear battery(between it's posts).

Looks like your passenger-side alternator is bad.

 

[87silverado]

alternator tested good

 

[doghead]

12.7 at the rear battery is not good, that voltage should be 14 or more.

 

[87silverado]

had the alternator tested at napa and it put out 14.7 volts
but i just cant figure out why my gen 2 light wont come on.
i cant find were the break in the circuit is.
have good continuity between main wire off alt to batt
there is another smaller red wire with a fuseable link at the same post on the alt. but i cant find were it leads to

 

[Skinny]

I would think that if you unplug the small connector and ground pin1 Brown wire the GEN2 lamp would illuminate with the key on. That would eliminate any dash, bulb, or harness issues out the the alternator related to the bulb not coming on. Once you get a result, then I would know which way to go with it.

Odds are that your alternator needs internal repairs if you went through the motions of cleaning up connections and testing the bulb in the dash. If you haven't done it, I would as a preventative measure rebuild both of them.

 

[doghead]

tested voltage at alts while running. driver 14.7 passenger 27.35

From this test, your rear alt is only putting out 12.65.

That is not enough.

Did you charge and load test your batteries?

 

[87silverado]

grounded the brown wire. light still didnt come on

 

[Skinny]

Sure, the alternator could have other secondary issues but this tells me you need to troubleshoot the harness, cluster, and check the bulb again. I would start by checking connections in the cluster, it is a very trouble prone area along with the large square plug in the firewall.

 

[87silverado]

well it works now. not sure what the problem was. i messed with about 5 different things so not sure what fixed it. cant wait for my cummins swap and get rid of all the hokey crap

 

[Skinny]

cant wait for my cummins swap and get rid of all the hokey crap

Not quite sure what you are referring to. Unless you are utilizing a self energizing regulator, you should know how to troubleshoot the charging circuit on your truck regardless of the engine that is turning it. GEN1 could have the same issue down the road that GEN2 is having. They are basically mirror images tied together in the middle as far as operation goes.

 

[lostinutah]

this post was almost awesome.....i have the same problem but not the same luck. any help?