I was told that while the engine is running,If you pull the posative cable off the battery and the engine stops running then the altinater is not charging. anyone ever heard of this?as my sons truck does this on his 85! Thanks,Allen Payson,AZ
yes this is true.....also check all the ground wires if one is loose or bad it might cause the same problem. there is also a hot wire on the fire wall just to the right of the carb check it too and the fuseable link. good luck... hope this helps.
I checked the battery with volt meter and it reads 12+ at the posts,with the engine running it reads around 11,(it should read around 13+ with engine at a little higher rpm is this right?) I checked wires at the turminal and seams ok but found one wire coming up to a relay and then into the turminal,I did take that wire and directly wired it to the truminal and bypassed that realy with still no luck! I checked all wires at starter and all look good with good connections. This thing is kicking my butt! Thanks again,Allen
you have done pretty much everything that I would of done... only thing I can suggest now is pullthe thing and have it tested at a parts house. The only other thing to do is check fuses and make sure the belts are in good shape...worn out belt will sometimes not spin right.
Thanks for the reply! I did take the alt off and had them test it (twice as a matter of fact.)still tested good and thought of the belt like you said too. Man what a Killer!Going to see if I can get a freind of mine over to look at! dont have the money for it but thing should be rewired is my guess! anyone know of a wire diagram onsite to look at?you can't even read what the fuse's are for on his fuse block all the lettering is gone. I do have a 79 parts truck long bed 2wd w/auto matic,would the wiring harness fit his 85 3/4T 4x4 4sp? Hey thanks again for everyones help, I usually am on the 55-59 site good people over there as well as here ,Thanks again guys!!! Allen&Ryan Payson, AZ
A Quick Way to see If Its Charging at all is to Place a Wrench on the center Bearing cap on the Back of The Altenater with it Running , Being Carefull not to touch any wires Or Connections Also Be Carefull not to Get Into the Belts of fan. If it Has a Fairlly Strong Magnatism Its Charging Wether its Enough or not Requires tests Much Like Youve Done . But If There is No Magnatism, Either It Has an Internall Problem or the Wires to & From it Have a Bad Connection. Best of Luck . Bob
The battery voltage unhooked (no cables attached) sounds normal. It is true that if the positive cable is removed that the engine will still run IF THE ALTERNATOR IS GOOD. The electrical system was designed for the battery to provide enough electricity to start the engine and thats all. When the engine does start the alternator takes over to run all accessories and to keep the battery at a full charge for the next time it's needed to start the engine. When the positive cable is removed and the engine shuts down this tells you that the engines' ignition was run off the battery by it's self. Thats why it read 11 volts with the engine running and no acc. on. If the alt. was tested and found to be ok, the electricity from the alt. is not making its way back to the battery.
