Bobcat 331 - Control panel glow plug light not working or countdown timer

[melli]

My battery was toast, so I try to jump start it with car...failed. While repeatedly trying to start it, the glow plug countdown timer stopped working. Off to store I go, and install a new battery. All I get is a hard click (magnetic switch at starter?). Won't start. Off to store I go, and replace a mess of fuses. No joy. I then swap out new hella relays for glow plugs and starter, and voila, Bobby starts up. Problem is, the glow plug light nor countdown timer on control panel work. I know the glow plug 'light' works (not burnt out), because the panel lights up when you turn it on. Problem is, I have no idea if the glow plugs are working. I tried running around to engine when I turn key 'on', but I read no volts.
Somehow I screwed things up trying to start it with a dead battery (too many on-off cycles fried something). Can anybody give me an idea where I should be looking to fix it? Wondering if control panel needs replacing? Or part of it?
If one roasts the glow plugs, shouldn't the timer and light on control panel still work? BTW - I read 2-3ohms on glow plugs.
Maybe more relays need replacing....idk

 

[007]

I'm surprised the starter relay fixed the problem as i would have said starter from the symptoms.
Are you sure the glow plug relay you replaced is a standard relay, as alot of glow plug relays have the electronic timer components in the relay??.

 

[melli]

I'm surprised the starter relay fixed the problem as i would have said starter from the symptoms.
Are you sure the glow plug relay you replaced is a standard relay, as alot of glow plug relays have the electronic timer components in the relay??.

The relays all have the same code...appear to be standard relays. Schematics indicate they are.
I started ripping things apart this evening. Can't see anything that would take out the glow plug circuit. Perhaps I fried the hot lead to glow plugs. A mystery. I need to pull out fuse/relay box and measure voltages to see if glow plug relay is getting power and able to switch it (send power to glow plugs).
The other thought was the control panel...I fried something inside that?
Thing is, the control panel appears to send power to glow plug relay, which in turn activates glow plugs. Everything else seems to work on control panel.
Problem is, there is no schematics that I know of, of the control panel. A bobcat proprietary thing....

 

[007]

If it was me i would be starting at the glow plugs and working up stream.
Some control panels can sense glow plug current by the way.
Long periods of cranking would more than likely damage the glow plugs not the panel or relays.
It is not uncommon to blow all glow plugs in about 10 seconds and if they are a bit weak they pop easy.
A DC clamp on ampere meter is good as you can just clip over the wires.
Confirm typical current draw by manually enabling glow relay.
Then check if relay is engaged when cranking with key.
Some control panels have a temperature sensor and if ambient is high they don't enable glow at all during cranking.
Since the panel is the worst case scenario i would rule every thing else out.

 

[melli]

If it was me i would be starting at the glow plugs and working up stream.
Some control panels can sense glow plug current by the way.
Long periods of cranking would more than likely damage the glow plugs not the panel or relays.
It is not uncommon to blow all glow plugs in about 10 seconds and if they are a bit weak they pop easy.
A DC clamp on ampere meter is good as you can just clip over the wires.
Confirm typical current draw by manually enabling glow relay.
Then check if relay is engaged when cranking with key.
Some control panels have a temperature sensor and if ambient is high they don't enable glow at all during cranking.
Since the panel is the worst case scenario i would rule every thing else out.

Sounds like a plan. Thx.
The glow plugs did cycle a few times when trying to start the thing.
I put in new relays, all around.
No power to glow plug circuit when starting.

 

[melli]

Update: wouldn't you know, I got 'lucky'. First time Bobby had failed to light glow plugs because ambient temps were high. Never gotten so hot before. And it happened while I was cranking on a dead battery, which blew a relay.
We got some overnight rain (cooler temps), and voila, the glow plug timer and light came on. So, Bobby is back in business. Thanks 007 for suggestions.
I'll blame it on global warming...haha
Seriously, where I am from, glow plugs always come on when starting a diesel. First time for everything. Relieved.