Battery discharges

[Smurfy]

I'm new to this sight, and I have 2 F-350 Powerstroke's a '97 7.3, and a '06 6.0, here we go with my favorite first!!! My '97 F-350 Power Stroke is discharging slowly overnight. Eventually I have to charge it. I had the batteries checked O.K. the alt. is putting out 14V, there is an 8V discharge when it is not running, I understand it should not be over 4V. I read where you disconect both negative cables from the batt, and put a test light between the post and neg cable, and if it is bright there is a short, and remove fuses one at a time until the light gets dim. I did it, and when I had gone through all the fuses, nothing happened and I'm looking at the test light, and it starts pulsating, and then it stopped and was dimmer. I believe it might have to do with the glow plug relay. Lately when you turn the key on by the count of 3, the wait light goes off and it is hard to start, and a lot of white smoke when it starts. where is the relay, and how do I test it??? Does anybody have any other ideas???

[DryHeatDude03]

I would suggest going back and redoing the test with a dc meter set to milliamp scale. Using a test light is not going to give you accurate results IMHO. You need to be looking for parasitic power draw from the batteries. IIRC anything over 80-100 milliamps is considered to be parasitic. Do you have an alarm on the truck? Any other afternarket accessories that have power draw with key off? Your radio and some electronic equipment obviously has keep alive memory that will draw when the truck is off. Make sure all interior lights go off,,i.e. glove box , courtesy lights etc. With an actual milliamp reading you will be better able to assess what is going on.