AC 60G GP question

[markrudella]

First off,

Thanks to the several guys that have helped me with my questions through PM and email. VERY much appreciated.

I've read through literally 70 pages of threads tonight, looking for any help and info about these vehicles.

I've acquired a 86 M1008 for use as a brush fire truck for my fire station. I was told to pick up AC 13G plugs, which after reading, I'm glad I didn't.

My question though, because now I'm confused - Can you put 60G plugs into a completely unmodified truck and have them work properly, or do you have to convert the GP system to strictly 12 volt?

There's threads upon threads about this, but too many people say one thing, and others say the other...

 

[Stihl029]

Hey our brush truck is a M1028, unfortunately the State has had it converted over to 12 Volt. I am not sure what we are running in it but that is besides thepoint since you are inquiring as to 24VDC. Let me know if you want any pics or what not about how its set up.

 

[m38inmaine]

AC60G's are fine, you will need to narrow/file down the spade connectors on them as they are a bit wider than the military plugs. Reguardless of conversion to 12v or not, the plugs are supplied with 12v.

 

[acmunro]

I agree 60G's work good for me. I put a new set in my M1008 in the middle of last winter and it has started and worked great.

 

[IRWFO]

Same here. Took out the original AC's and installed the Wellmans. 4 of the 8 failed the first week. I reinstalled the AC's and all is good now.

 

[FMJ]

opcorn:

 

[2deuce]

I had the same problem with 4 wellmans burning out the first week. I'm not sure it was the plugs fault. My connectors to the plugs seemed very weak. I replaced those and put in some old plugs that were still good and have been fine since. I thought there was 24 volts going to all the plugs. Making it 3 volts to each plug and if one plug burns out it ups the voltage to the rest. Please correct me if I'm wrong.

 

[Michael]

I had the same problem with 4 wellmans burning out the first week. I'm not sure it was the plugs fault. My connectors to the plugs seemed very weak. I replaced those and put in some old plugs that were still good and have been fine since. I thought there was 24 volts going to all the plugs. Making it 3 volts to each plug and if one plug burns out it ups the voltage to the rest. Please correct me if I'm wrong.

You are wrong.

The glow plugs would have to be hooked up in series to work the way you describe. They are not. The 8 glow plugs are connected to a voltage dropping resistor that is calibrated to 13G glow plugs. I don't think 60G glow plugs are different enough in load to be a problem but some do. If a glow plug burns out or accidentally gets unhooked or develops a high resistance at the terminal due to being loose?, the voltage will increase to the remaining plugs. This allows more current to flow through them and makes it more likely that another will burn out until they are all gone.

Some others and I have noticed an increase in glow time when they changed to 60G plugs. If it is not excessive the current limiting feature will protect the plugs. They shouldn't stay on much longer than the seat belt buzzer. And don't go by the light, listen for the click of the relay or watch the volt meter.

I had one that stayed on 2 to 3 times as long as it should have and it still lasted a year. I think I may have had a bad temp sensor, but I just went to a manual system.

 

[IRWFO]

They shouldn't stay on much longer than the seat belt buzzer.

You have a seat belt buzzer?

 

[markrudella]

Well, before I was able to read all of the threads, I decided to convert the GP system to 12v. I hooked up the new relay, and still had no power. I jumpered the relay, and now had power, so I replaced the module card today, and the system works perfectly.

 

[Michael]

You have a seat belt buzzer?

Most of the time. It takes spells of working and not working.

Five to 10 seconds depending on how cold it is for those that don't.

Mine was staying on almost 60 seconds and wouldn't just click of, but made kind of a buzz for second or two. Finally the relay died along with all the glow plugs. Replace them all and it still stayed on too long and buzzed at the end so I just went to a push button. I didn't do anything that can't be undone so I may fix it right one of these days.

Well, before I was able to read all of the threads, I decided to convert the GP system to 12v. I hooked up the new relay, and still had no power. I jumpered the relay, and now had power, so I replaced the module card today, and the system works perfectly.

I also did the 12 volt conversion when I did the above repairs. I taped off the resistor wire and made a new jumper wire to the 12 volt buss. Like anything, there are advantages and disadvantages. You do put a lot of load on the front battery but at least you shouldn't burn out all of your plugs all at once.

 

[2deuce]

Michael, If all the glow plugs and connectons are working correctly how many volts are each recieving? If one burns out then how many volts would each plug recieve? When 2 burn out does the voltage to the remaining go up again? Or is it that the voltage remains constant when a plug burns out but the current increases to the rest.
Thanks

 

[Michael]

They all see the same voltage since they are hooked up in parallel. I don't know the exact voltage, but it is about 12v. I think both the voltage and current per glow plug goes up as each one burns out. Total current would decrease.