I´m restoring this 1968 D4d. I´m not sure how the amp gauge is hooked up with the start/heat switch. Can any of you guy´s remember if the amp gauge goes to "discharge" when you switch on the glow plugs? I dont know if the gauge can handle the amperage that goes to the plugs or if I have to bypass the gage for the plugs. in some machines I have worked on the needle goes to discharge when warming the glowplugs but on other it don´t. How was it on the D4d? Thanks. Walter
Yes it should discharge with glow plugs. The draw is 5 amp per plug on 24 volt system. Get a 60 amp meter if you want to be sure. Hook one side to bat and alt plus all loads to the other side. Later Bob
My '73 D 7F/ 3306 shows discharge when glowplugs are on and before cranking. It shows -30 amps when the batteries are up good and a little less if they are not fully charged. It's a 24 v system. You need good heavy wire supplying the start/heat switch, and on to the glow plugs and also a good ground circuit all the way back to the batteries, so be sure the engine is well-grounded to the tractor frame and whatever else it takes to get the full available battery current both to the glow plugs and the starter. Bolted or riveted joints in the frames and structure of older machines may not provide good electrical conductivity even if they are tight. Rust and dirt are great insulators.
Great thanks for the answers. Just what I needed to know.