glow plug relay?

[primer grey]

Hi there,
I replaced the glowplugs in my 82 sd22 720 last week, and saw much improved starting immediately and ran all week with no problems.
Today is about ten degrees colder than it has been, and turning on the ignition gives me just a quick flash on my glow indicator lamp on my dash.
The starter will turn over just fine, and the wipers and headlights work, so the battery is ok, but the heater won't blow and the plugs won't glow.
odd, eh?

the plugs all still seem to be firmly in and attached, and in the interest of full disclosure -not that I think it has anything to do with it- i also recently installed an engine heater in the radiator hose.

This is my second sd22 truck, and I've been driving this one for a couple years now. I was beginning to feel like I've got these trucks all figured out, but this is new for me.
anyone out there ever had a similar situation?

Thanks.

[asavage]

. . . turning on the ignition gives me just a quick flash on my glow indicator lamp on my dash.

I've seen several SD 720s with bad GP wiring connectors. The first thing to do is put a test light or voltmeter on the GP bus (any GP tip will do) and watch it while a helper turns the Ign. ON.

The fusible link connector at the positive battery terminal is the most troublesome spot of trouble. Here's a pic of the fusible link terminals on a member's rig (the white-ish connectors):


The round GP relay is nearly trouble-free, and I've never seen or heard of a bad on on a 720 SD.

Hope this helps.

[charmalu]

I had trouble with one of the fusable links one time, don`t remember what now, too many yrs ago.

But did have trouble with the GP harness plug near the firewall. I made a new harness that connects to each GP. seem like the plug got corroded, and was burnt.

Just because the light goes off for the plugs, the relay may still be on. wait until you hear the clunk of the relay going off.

There is a plug that comes down under the steering column from the ignition switch. sometimes my blower and wipers wonts work. wiggle the plug, and all is well.

Charlie

[asavage]

Yes, there is IIRC another one of those bastard spade connectors between the GP relay and the GP bus. Same problem: heat and time make them give up. Can be bypassed with a good crimp connector or solder job.

The fusible link ones at the battery seem to give trouble the most, though.

[primer grey]

yes, a good crimp connector did the trick.

Thanks for pointing me in the right direction, it is much appreciated!

[asavage]

Someone should probably write up an "SD 720 FAQ" for these common problems, similar to the "LD FAQ".