Power distribution center burnt up

[Daleb]

Hi drove my 1999 3500 24v truck to work the other day and parked came back to it in the evening and whent to start it, first thing i noticed was no wts light.It turned over but fail to start and no fuel pump and no bus showing in odometer. Popped the hood and could smell burnt wires. The joint connection 2 in the pdc burned up the local dodge dealer told me that usually the pdc gives out 90% of the time the pdc shorts out its self and causes this but I'm not sure about that. I got a good used one from a local parts truck my plan is to clean all the grounds and check for shorts then I will hook the batteries back up and pull what codes i can. Just wondering what else i should do to prevent it from happening again or does anyone have an idea what might have caused it in the first place.would be thankful for any feed back.

Dale

[Mopar1973Man]

Can you post pictures of the burnt unit so I can possibly figure out what subsystem caused the issue?

[Daleb]

Is beside the fender on the lid it’s calls it joint connector 2

[Mopar1973Man]

Here you go... Joint Connector 2 is at the top. As you can see its a power feed. for the ECM and PCM. Double check your fuse #3 make sure its the right size. 

 

 

As you can see the devices in this map. Watch for the connection DOT those are connected but lines without the dot are not connected. 

[Daleb]

Thanks will try to sort it out

[JAG1]

Maybe an irrelevant question ..... could a deteriorated grid heater cause this problem? My first gen truck ended up with all fuseable links burned to a crisp from the grid heater. Soon as I repaired and unhooked the grid the problem went away.

[Mopar1973Man]

1 minute ago, JAG1 said:

could a deteriorated grid heater cause this problem?

 

No. Grid heater is outside the entire PDC system with its own fusible link on the battery terminal. 

2 minutes ago, JAG1 said:

Soon as I repaired and unhooked the grid the problem went away

 

Most likely you have a bad grid heater solenoid in the mix too. Hard to tell now being the truck is gone. 

[JAG1]

We need to understand what caused this on Daleb's truck especially if this is a common problem according to what the dealer said.

 

BTW...Welcome to the forum Daleb.

Edited October 9, 2018 by JAG1

[Daleb]

I was thinking about it being the grid heater. This is a summer truck so I’m not going to hook the heater back up. No need to have that huge power drawe on a 20 year old truck when not needed. As I start to remove the old wire harness the ground under the left battery was in bad shape only thing holding all the wires to the connector was black tape. Would a bad ground cause the damage?

 

[Mopar1973Man]

Typically something gets hot because of a few problems.

• Weak connection, rusted connection or corroded connection.
• Wrong fuse used or too high of amperage.

Like I was talking to @dripley on the phone last night and reminded him of the 1970's fuse issues we had in the past. Like my old 1972 Dodge pickup was popping the blower motor fuse (now I know that means the bearings are failing). But... I knew that I had to use the proper 20 amp fuse for that circuit. End result was the blower motor fuse and wiring went up in smoke.

 

Did you know that glass cartidge fuse were given up because of double rating for the blade style ATC fuses? What caused my failure in the 1972 Dodge was that I grabbed a 20 amp 120V fuse and not a 20 amp 12V fuse. What the difference Wattage it takes to blow the fuse. 

 

120 volts x 20 Amp = 2,400 watts to blow the fuse

 

12 volts x 20 Amp = 240 Watts to blow the fuse

 

So the circuit had 10 times the power now and I let the Magic Smoke out of the Wiring. 

 

Back to the OP issues... You can have a weak connection somewhere and mass amount of heat is generated from current flow. Back to the weak connection issue. 

[JAG1]

Wouldn't the weak connection show its location by determining where the fire started or initial hot spot?

[Mopar1973Man]

1 minute ago, JAG1 said:

Wouldn't the weak connection show its location by determining where the fire started or initial hot spot?

 

Yes. So in the OP case the joint connector #2 is the weak connection where the hotspot burned the joint connector. Also the problem line will be the one that took the most heat. 

[Daleb]

I have only owned this truck for a couple months and am not totally sure of its history. The only other thing I noticed was the wipers came on by themselves that morning. Thought it was just a dirty switch at the time because I read somewhere that was common. Also now that I’m going through  the fuses the a/c fuse is blown and also one blade is broken off and seized into the pdc

I will follow the burnt wire inside the pdc later and see where the go. 

[JAG1]

So when Dale gets everything back together, making sure #3 fuse is the right size, he should also see whether connector #2 is getting warm again? and be ready to unhook the battery as a precaution? Or like you say the initial damaged area of the heat source shows it will be eliminated with the new PDC?

18 minutes ago, Mopar1973Man said:

 

Yes. So in the OP case the joint connector #2 is the weak connection where the hotspot burned the joint connector. Also the problem line will be the one that took the most heat. 

Based on what your finding Dale, I would go thru and check everything you can.

Edited October 9, 2018 by JAG1

[Daleb]

I checked all the fuses and they are the right sizes.I traced the worst burnt wire from joint connection 2 and it goes to 20amp engine control 2.It goes in but no wire is coming out the other side of fuse block but the replacement pdc is set up the same so it must be normal. Also I'm confused why it would not have blown the fuse instead of burning the pdc.

Edited October 9, 2018 by Daleb

[JAG1]

Yes thats a good question unless the hotspot had to be elsewhere in the burned wire, according to what Mike is saying, was a weak connection or area with greater resistance than the fuse.. Just not altogether sure, so trying to learn all I can here.

 

It would be good to be able to test that fuse that let the wire burn and see if it is faulty. I doubt it tho.

Edited October 9, 2018 by JAG1

[Daleb]

I tested it with my ohmmeter and it was ok

[JAG1]

I mean test the fuse to see what amount of amperage it does blow. I would put in a new fuse any way. What has me concerned is not knowing for sure what caused the short. Brings me to thinking that I want to put in a lower amp fuse to help protect it more. You might think about doing that anyway.

 

Mopar1973Man, any thoughts?

[Mopar1973Man]

Could of been a weak connection between the fuse and joint connector #2. A weak connection will make heat.

[JAG1]

7 hours ago, Daleb said:

I tested it with my ohmmeter and it was ok

Daleb, where is the lift pump hooked up to? Is it directly from the ECM? or is it powered by the battery through a relay triggered by the ecm? This is rather important.