Just got done replacing the heater core on my truck and now when i start the truck after about 8 minutes of running the check guage light comes on and volt guage goes all the way to the left. Reading 12.6 at batteries with them disconected. Getting 12.6 at batteries with truck running and also 12.6 on back of alternator. Any ideas, got to work in the morning. Went over all the connections under the dash and didn't see anything left loose.

 

Also just took the alt. in and had it bench tested and all passed. Any ideas?

 

Did you get both connectors fully plugged in on the back of the dash? Did you check all the fuses?

 

Well this is wierd. Put alt. back on after bench tested and everything works great. Doesn't make any sense because it was never taken loose. I didn't pull dash all the way out, just pulled loose and suspended to grab handle on passenger side. What 2 connections are you refering to incase it happens again.

 

just going for the basics here, for this truck:

ground issue. if plugs at heater core/dash line were not fully inserted, the short would try to loop back through a ground at the alternator. pulls a 25 amp, so as above- check the fuses next time. just for giggles, check the grounding strap condition underneath, at the passenger rail of the frame.

just a basic thing-

 

Did you take the connection block by the brake/clutch pedals loose? It is secured with a bolt in the middle and has caused me loads of grief. It will act like its in but without the bolt tightened it will cause random electrical issues.

 

Thinking this was the problem. I went back and checked all connections even the ones i did not disconnect. Charging normal and have heat without the antifreeze smell.