Military Vehicle Repair: M1008, o reilys auto parts, o reilys auto

Question
I have read one of your answers on the M1008 electrical system and was wondering, I have one with 24vdc at the glowplug relay, apparently the resistor is not working.  The glowplug relay is froze on and all glowplugs are burnt, my question is does it take standard Chevy glowplugs and is the relay 12vdc fired or 24vdc fired?  Also since my resistor is shot can't I just take the input wire for relay and hook to 12vdc side?


Thanks,

Chris E. Gaines
Magnet Cove Area Fire Dept.
www.magnetcovefd.com


Answer
Hello Chris,
I am a firefighter also, over here in Oklahoma. Checked out your home page.

That big resistor will show 24 volts when not loaded, but when the glowplugs are on, it will have 12 volts there.

But I don't use them usually. I tap directly to the 12 volt supply right there on the firewall, and it works great.
The relay is 12 volt also, and there is a replacement relay available at "O"Reilys Auto Parts. Very reasonably priced, but make sure you get the isolate field relay, not a Ford starter relay. I have one laying on my desk at work, but the number escapes me.

The glowplugs are standard....I think 13G, but don't take that to the bank. I haven't needed to replace any in about three years. (I run six of those trucks).

Something made your relay stick closed. I would want to find that problem before replacing the glowplugs, and get it corrected, or you will burn out the new ones pretty quick.

If the relay is just welded closed, it will show continuity through the large terminals after unhooking all the wires. Be gentle when doing that, so you don't jar the contact loose and spoil the test.
If it is welded, just replacing the relay with a new correct one might fix you up.
But if the controller is keeping it engaged, you will need to repair or replace that before continuing.

I have communicated with one fellow who is using a momentary button to manually control the glowplugs himself, and seems to be having good luck with it.

If your relay has been replaced at some time with the little square plastic relay, like the one from a 1010, throw that thing away, as they melt internally from the load, and will cause problems.

If you would like to call me at work and talk, I am Richard VanNatta, known as "Van", at 580-429-3007, or 429-3222. I am the mechanic for the Wichita Mountains Wildlife Refuge.

Van