M1009 ignition circuit problems

[FTWTechnologyInc]

While installing a radio in my 1984 M1009 CUCV, I was using a small pneumatic reciprocating saw to cut out the plastic panel. Apparently the vibration caused the starter relay under the dash to go into the "CUCV phantom start" mode and the motor started cranking. I got to the battery wires as soon as I could and yanked them off the terminals to interrupt power to the starter motor.

I got on here and read about the starter relay fix and that rang a bell with my memory when I was in the Army from 1984-88. I wasn't a 63B but drank a lot of beer with a couple of them and as I remember it the PM shop's fix was to replace the stock relay with another (defective) one from inventory when one encountered a self cranking CUCV.

Anyhow, I replaced mine with the Heavy Duty Wheel Horse relay just like the DogHead tech article specifies. I had to snip off an inch or two of the fuseable link wire from the rear battery to the Engine Wiring Harness Block on the firewall which had burned away from the terminal connector.

I reconnected the battery cables and the thing has worked like a champ since. That was until a couple of weeks ago. I started her up to head into town about 12 miles away and got to my destination with no indication of any problem. I shut it off to go to the hardware store and was inside for 10 minutes or so. After I returned to the parking lot, I started it up and was on the way out when I remembered an item I had forgotten, so I parked the truck again, shut it off and went inside. When I returned in 5 minutes and tried to start it, the starter relay would engage but the starter motor was a no go.

After getting it hauled back to the farm on a rollback. I pulled the starter and the solenoid was cracked and shorted. I figured it had gotten fried from the Phantom Start episode earlier and the motor probably wasn't too far behind so I decided to replace both of them. I installed the new starter/solenoid and reconnected the battery cables. When I turned on the ignition, no lights illuminated on the dash and the starter relay was a no go. I looked down at the radio face plate and it was illuminated. Apparently I had left the radio on for the past week and had ran down both batteries.

I charged the batteries over night, then reconnected the cables. I turned on the ignition and all the normal lights came on. The glow plugs cycled, I cranked it over and it fired right up. Both generator lights went out so I assumed the alternator was working properly. I drove into town (about 20 minutes away) had lunch and returned with no problems and parked the truck. About 3 hours later, I went to start it and the batteries were dead again.

I charged the batteries again. This time when I turned the ignition on I saw a puff of smoke coming from the Engine Wiring Harness Block location, so I turned the switch back off. The fuseable link was hot to the touch. I took a voltage reading at the terminal and there was about 2 volts. I disconnected the fuseable link and when I did, the connector came off of the wire which had burned in two. So, I replaced the fuseable link with a fuse block and a 30 amp fuse. When I reconnected the now fused wire from the rear battery negative terminal to the engine wiring harness block, the connector sparked pretty good like there was a pretty heavy load on it or a short to ground.

When I turned on the ignition, all the normal dash lights came on and then went out. I checked the fuse and it was blown. So I jumped across the fuse block with a 10ga wire. When I turned on the ignition all the normal lights came on. The glow plugs cycled, I cranked it over and it fired right up.

I shut it off and then disconnected all of the wires from both sides of the engine wiring harness block and checked them for continuity to ground in both directions in case there was a diode in line anywhere. Lo and behold there was a dead short to ground on the 3 red 2A wire which I believe runs to the ignition switch and also the under dash fuse panel. Also, I get 24 volts from the only blue wire which connects to the engine wiring harness block, which I believe runs from the negative power bus for the alternator charging circuit.

My question is has anyone experienced this problem and or have any idea where to look for the short to ground on the 3 red 2A wire which is obviously draining the batteries when the engine is not running? Thanks in advance

 

[lavarok]

Why were you using a saw to remove the plastic plate? If you removed the black trim, there is a bracket holding the block off plate in place. Remove bracket = hole for radio. Mind you, its for an old style knob radio so you would have to cut some metal for a newer style...but the black trim should have been removed first.

Are you sure you didn't cut any wires behind the dash by mistake?

As for your problem at hand, I'd start by removing the plug from the driver side ALT and check for the short. If still there, do the same on the passenger side. Then proceed to remove fuses from the fuse block and check for the short until you isolate the trouble circuit.

 

[Warthog]

First off, do a load test on your batteries. There could be a dead cell that is draining them.

Second, where did you get power for the radio?

Wire 3red2A is a 12 gauge wire that splits into three circuits. Two that feed the ignition switch and one that feeds to the fusebox for the Rear Air on the M1010s. It is empty for the M1009s.

The 30amp fuse for the fusible link is not big enough. The manufactures use the BIG 40-60amp units.

Here is the circuit path.

From the negative terminal of the rear battery to the 12v ENG WIRING HARNESS BLOCK - 12V (supplies 12v to all of the 12v stuff on the truck) - 12 gauge BLUE fusible link

From the 12v BLK to the firewall plug - 16 gauge RED fusible link and 12 gauge RED regular wire

From the firewall plug in to the dash wiring harness - splits into three circuits

Two 12 gauge RED wires go to the ignition switch
One 12 gauge RED wire goes to the fusebox for the rear A/C

I would make a map of all the fuses and remove them and replace them one at a time to find the "bad" circuit.

It could be any number of things.

 

[FTWTechnologyInc]

radio power and saw?

Power for the radio is from an open slot, 4th one down on the right side on the fuse panel. It is also fused in line. I unplugged this power wire from the fuse panel and now the short to ground on the 3RED2A wire is gone. I am guessing that the power supply on the stereo is passing voltage to ground even when it is powered off? I wonder if I could add a diode to this power wire or the radio ground wire to keep it from passing to ground? My truck has one heavy 6 gauge wire running from the Engine Wiring Harness Block which runs to the drivers side alternator which I get 1 Kohms one direction and 0 in the other. I am guessing this would be correct since there is usually a diode in line with charging circuits.

I had to cut the sheet metal away from the bottom edge of the dash to accommodate the new digital stereo receiver. I checked before and after cutting for any wires behind the panel and there were none. That was the first thing I thought had happened but as we all know it was just the vibration itself that initiated the rampant CUCV Phantom Starter Relay energization. - Thanks

 

[Warthog]

Power for the radio is from an open slot, 4th one down on the right side on the fuse panel. It is also fused in line. I unplugged this power wire from the fuse panel and now the short to ground on the 3RED2A wire is gone. I am guessing that the power supply on the stereo is passing voltage to ground even when it is powered off? I wonder if I could add a diode to this power wire or the radio ground wire to keep it from passing to ground? My truck has one heavy 6 gauge wire running from the Engine Wiring Harness Block which runs to the drivers side alternator which I get 1 Kohms one direction and 0 in the other. I am guessing this would be correct since there is usually a diode in line with charging circuits.

The forth fuse down on the right of the box shows to be #10, which is the Gas Particulat Filter and A/C fuse for the M1010.

Sounds like you have an issue with your radio. Does it have a memory feature that requires a hot fuse at all times?

 

[FTWTechnologyInc]

Yes that is the location I was tapping into for the radio power. Yes it does require power full time for memory functions. I have run this setup for about 8 months or so without any problem. Maybe something went south with the power supply in the radio? I try to find out what the load is supposed to be. - Thanks for your help

 

[Smokingman]

The 30A fuse is not large enough.Trust me I tried this as well it will blow in very short order.I found fusible links at napa of the appropriate size.

Second it sounds like your front battery ground is bad(did you melt down the post?).Clean where it attaches in front of the battery,and the lead that goes to the frame.Then I would go one step further.Run a new 8 gauge ground wire from the front battery(negative) straight to the frame(use a self tapping screw and hit the frame with a sander for a clean contact).I had many electrical problems.I ran the second ground from the battery to the frame and another from the drivers alternator to the frame.I left all original grounds intact as well.This solved my many electrical issues.

 

[FTWTechnologyInc]

I put in a fuseable link and cut out the fuse. The fuseable link gets warm during GP Cycling but cools off during normal operation. Everything seems to be working normally now. I think what happened when the Phantom Starter Relay event occurred, the main power wire running to the EWHB got burned along with the old fuseable link wire.

I had the batteries load tested and they are good. The alternator is putting out 13 - 14 volts as well.

I was curious what the front battery frame ground wire has to do with my radio power shorting to ground?

Thanks

 

[ctmustang]