Weird battery issue

[firefirefire90]

I have a 1986 M1009 with a peculiar problem. I have one bad battery which is the one hooked up to the starter and if I jump it then the truck starts fine with out problems. Now if I flip the batteries and try to start the truck, the glowplug relay starts going crazy and makes this horrible grinding rotating noise. Any reason this could be?

 

[doghead]

Unless you have done a full 12 volt conversion, your truck uses both batteries to start(24v starter).

The glow plug controller uses one battery to operate(front). If your front battery is dead, it may cause relay chatter.

You may have a charging issue. front battery, drivers side alt, and rear battery is charged by the passenger side alt.

 

[firefirefire90]

Interesting deduction Mr. Doghead. I need to replace my belts then I can figure out my charging issue to the rear battery. Interesting that a low charged front battery would cause the chatter.

 

[idM1028]

Interesting that a low charged front battery would cause the chatter.

Not really if its using 12 volts as established by Mr. Doghead. When I start my truck up I can hear the GP relay clicking (as it should) and the voltmeter going crazy. Green, yellow, green, now yellow... I do know there's a 24V wire that attaches to the GP relay, but that's a story for another day.

 

[firefirefire90]

Not really if its using 12 volts as established by Mr. Doghead. When I start my truck up I can hear the GP relay clicking (as it should) and the voltmeter going crazy. Green, yellow, green, now yellow... I do know there's a 24V wire that attaches to the GP relay, but that's a story for another day.

lolwut? I've never heard it click until I drained one of the batteries.

 

[Cucvnut]

i know what IDM1028 is talking about. when you start up it supposed to cycle liek that.

 

[TGP (IL)]

You need to remove,charge, then load test both battery's.
And replace as necessary, and always' should replace battery's in pair's when multiple battery's are used.

Messing around with weak battery's in a 24V system is asking for Major problems.

As far as charging issues you said you know you need belts. Do That.
But does both Gen 1 and 2 lights come on when the key is first turned on?
If so your charging issue is, belts.
If not follow the TM's to diagnose the charging system.
TGP

 

[idM1028]

lolwut? I've never heard it click until I drained one of the batteries.

Might want to look into that. I replaced mine a while back. Cost me like $30 at NAPA. Check the FAQ thread or the wiki for the part #. You should be able to hear it with the wait light on. Its on the firewall up high on the driver side, so if you hear a loud clicking from there, you know its working. That and you should be able to see the electrical draw with the voltmeter. Not sure what the official number is, but mine cycles 4 times before it stops.

 

[Terracoma]

idM1028 is referring to "afterglow", when the glow plugs cycle after the engine starts.

Afterglow is normal, but will vary in length/cycles based on how warm the engine is.

 

[firefirefire90]

I just get one loud click/thump about 3-5 seconds after the wait light turns off. Is that what you're talking about?

 

[idM1028]

I just get one loud click/thump about 3-5 seconds after the wait light turns off. Is that what you're talking about?

Probably, but best thing to do is watch the voltmeter. Does your voltage change when you hear this clunk? If so, then yes that is your GP relay kicking in.

-Ian