Archived Gen lite comes on after 1/2 mile driving and stays on

[GPaye]

The gage in still in the white operating range but at the low end, approx 12 volts. Batteries are 4 years old and when checking the batteries with a hydrometer each have 3 cells over 12. 5 and 3 cells between 12 and 12. 4. If it was the batteries wouldn't the gage be above 14 volts when driving? the alternator is not noisy and the belt is tight. Can you steer me in the wright direction please, or should I take it in to the dealer and have them check it out.

Thanks,

Gene

 

[p-Bar]

I would pull the batteries charge them both independent of each other and take them to a parts store that will do a load test.

Also if you have a small voltmeter put it on the battery or other power source on the truck and see what kind of voltage you are getting . Should be around 14. 3 or so

 

[bmoeller]

Check the 120 amp alternator fuse under the hood. Could be blown. Will do what you are experiencing.

 

[GAmes]

Try disconnecting the big wire to the grid heaters from the battery. If you get a normal charge one or both of the relays has failed and/or the PCM is sending a constant gound to them. This is a shot in the dark since you fail to show any info on your pick-up.

 

[GAmes]

Well GPaye, welcome to the TDR. FYI, it is protocol to respond to posts, especially in 911, to see if any solutions worked. There is a wealth of knowledge available, but not much use if we have to guess at what is going on.

 

[GPaye]

Well many thanks for the info, ended up changing both batteries, still had same problem. Had the alternater checked and was only putting out 12 volts, replaced the alt, still not charging, replaced the fuse for the alt, the bolt on one, and all seems to be working. Also got a new computer so now I can respond to all the help offered several weeks ago. Again, many thanks and happy and safe holidays to all. Gene