96 battery disconnect switches

robp823 · April 28, 2011

Have a 96 f-250 and the customer wants battery disconnect switches installed.Anyone ever do this on a 7.3???Im really not sure how to go about it looking at the cables with some of the terminals and more than one cable or wire coming out.Any help appreciated.

lmorris · April 28, 2011

Typically there should be one wire going from the passenger battery positive terminal to the starter relay on the fender. This is your power feed to everything on the truck but the starter itself. You should be able to put the disconnect switch inline with this wire. If there are other aftermarket accessories wired directly to the battery move them to a junction point after the switch.

robp823 · April 29, 2011

thats little wire going to the relay powers everything on the truck???

Brad Clayton · April 29, 2011

Robert, I would suggest having this customer get in touch with your local ambulance builder. They have the best, safest and most reliable disconnects and most aren't available to the general public.

I would say that just by the way your questions and answers are reading in this thread, you are opening yourself and your dealer to a potentially huge liability. On a cold morning, these diesels will pull an incredible amount of amps after starting and glow plugging, and I think local parts store stuff will end up burning this truck to the ground.

lmorris · April 29, 2011

It might be easier to tell him to just disconnect the batteries.

Jim Warman · April 30, 2011

Yes... remeber that the RUNNING requirements (especially on older vehicles) is much lower than the STARTING requirements.

Bringing us to point number one. What does the customer think he needs/wants and what does he really need? Is his concern a parasitic draw? Is he looking for a theft deterrent? Does the truck sit idle for extended periods and he's looking for a way to reduce 'normal losses'? Does he have a real requirement for disconnecting the main starter feed? Or is disabling the the other 99.9% of the electricals sufficient? (Notice that a stock 7.3 has only one power "tap" at the right side battery - later trucks have power taps from both batteries).

"Most" available manual disconnects are rated for 100ish amps continuous duty and surge loads to 500 or so amps - higher ratings are available but the minute you start shopping for "emergency vehicle" parts, the price goes up.

If it's a theft deterrent, a little creativity is all that is needed.

FWIW, if the customers concern is parasitic draw, you would be further ahead to try and have him fix the concern properly just in case the parasitic draw is just the tip of the iceberg.