Need electrical advise on M1008 please

[victor3ranger]

I started my M1008 yesterday morning and everything was fine, nothing out of the usual. The truck was covered in 1/2" of ice so I turned on the defroster on high and let it idle for a while to warm up.
after about 15minutes I went out to check on the truck and get the ice off the windshield, everything was still good. After removing the ice from the widnshield I tried to activate the wiper blades and they didn't move. That is when I noticed that the heater wasn't blowing anymore. I looked at the AMP guage and it wasn't reading at all. At this point I checked all the fuses under the dash, all the blade fuses were good, then I checked all the fuses that were in-line under the hood, those too were fine (at least the ones I could find).
I turned off the motor and noticed that I now have no powere to anything.

What would cause this and what is the fix??

 

[porkysplace]

Check your fusible links.
[h=1]Fusible Links - 101[/h]There is more electrical info here
[h=1]CUCV Helpful Threads[/h]

 

[victor3ranger]

Porky, is there a place the shows where the fusible links are located??

I am betting that this is my problem, now I just have to figure out where they are located so I can repair/replace what I need.

 

[porkysplace]

Porky, is there a place the shows where the fusible links are located??

I am betting that this is my problem, now I just have to figure out where they are located so I can repair/replace what I need.

This has the wiring diagrams
[h=1]CUCV Wiring Diagram color (except M1010)[/h]

 

[victor3ranger]

Porky, in the diagrams, when it says suppresor, does that mean it is a fusible link?

Also, if I have lost ALL electrical powere to everything which diagram should I be looking at?

 

[goldneagle]

The usable links were blue in color if I remember correctly. I think the suppressor is the group of capacitors next to the wiper motor assembly. You can bypass them if you want. They plug in line.

 

[Warthog]

The Fusible Links - 101 threads has all the links listed. You have to look at the corresponding diagrams to find them. There is no thread with a visual picture of the locations. You have to look for them.

Two main places to look for fusible links are at the 24v terminal block behind the rear battery and the diamond shaped 12v terminal block on the firewall next to the glow plug relay.

The first thing I would do is check the status of the front battery. You may have drained it. Always make sure you batteries are fully charged and load tested before starting any electrical troubleshooting.

The next thing I would look is the main 12v feed from the batteries to the 12v terminal block. It is the 8 ga wire coming from the batteries to a blue 12ga fusible link at ther 12v terminal block. Use Diagram E-1 or F-1 to locate it.

No telling which fuse broke and will need to be replaced. Did you know that the heater and GEN1 exciter circuit share the same fuse?

Fusible links are different colors depending on the wire gauge. They are also list in the 101 thread.

A suppressor is a capacitor. It is not a fusible link. Read the 101 thread it helps explain how to read the diagrams and what to look for.

 

[victor3ranger]

Thanks Warthog. I was going to check the batteries out this afternoon when I get back home. I know they were both fine when I started the truck right before this happened but who knows now.
After that I will start trying to track down these fusible links.

 

[royalflush55]

I would check the Diagram E-3-1 Red2R-12 volt engine wiring harness block-12 volt to ignition switch- 16 ga. fusible link. This is one of the fusible links that comes off the 12 diamond on the firewall by the glow plug relay. It goes to the ignition switch on the column. These fusible links can look ok and still be burned inside. Pull on them slightly when you locate them and if they pull into or stretch a little you have found one of your problems.

 

[victor3ranger]

I would check the Diagram E-3-1 Red2R-12 volt engine wiring harness block-12 volt to ignition switch- 16 ga. fusible link. This is one of the fusible links that comes off the 12 diamond on the firewall by the glow plug relay. It goes to the ignition switch on the column. These fusible links can look ok and still be burned inside. Pull on them slightly when you locate them and if they pull into or stretch a little you have found one of your problems.

Does that fusible link go all the way up into the column?? If so, how do you replace it if it goes all the way up there?

 

[Warthog]

Fusible links are only around 6" in lenght.

The one he referred to is at the diamond shaped terminal block on the firewall.

 

[royalflush55]

No. All fusible links are no longer than 9 inches. The original fusible links are connected to the wire by a hard plastic connector. All you have to do is cut these off and replace with the same size fusible link. I was just trying to point out which one might be burned into. I had this one to go bad when my M1031 was running with heater fan on high also. Good luck!

 

[victor3ranger]

No. All fusible links are no longer than 9 inches. The original fusible links are connected to the wire by a hard plastic connector. All you have to do is cut these off and replace with the same size fusible link. I was just trying to point out which one might be burned into. I had this one to go bad when my M1031 was running with heater fan on high also. Good luck!

When this happened to yours did you lose all electrical power to everything in the truck?

 

[royalflush55]

Yes. Everything that is powered from the switch went dead. Fuel pump solenoid closed and truck died. Voltmeter showed nothing and the gen 1 and gen 2 lights would not light up. Heater fan quit working. The fusible links looked ok but when I pulled on them slightly and one stretched and pulled into. I remember this being a red fusible link on a red wire.

 

[MarcusOReallyus]

The fusible links looked ok but when I pulled on them slightly and one stretched and pulled into. I remember this being a red fusible link on a red wire.

This is important. A fusible link can look okay and be deader than a doornail.

 

[victor3ranger]

This is important. A fusible link can look okay and be deader than a doornail.

Well, I checked out the front battery and it was totally dead. So I charged it all night, the next morning it showed 100% and it started up just fine and everything seems to work like it is supposed to. Only thing I can think of is the front battery must be toast and was drained when I turned on the heater fan and wipers.
I also checked the bast I could the fusible links and didn't find any that were bad.

 

[cucvrus]

Just like mentioned before. you will need to check the fusible links carefully or with a voltmeter,ohm meter or test light. The outer coating may still be intact and the core is burnt thru. I also had things on the 12 volt side that were drawing power and killing the front battery only. Check carefully. I always go for any modifications that were done and see if they are drawing current when the key is off. A bad alternator can also cause a dead battery. I never had it happen but I seen it on new cab chassis units. We had several start fire while sitting parked and burn 10 to the ground over night. GM did a recall on that model year. It was a defective alternator issue. sevaral thousand units needed the updated alternators installed. Good Luck and I with you Happy New Year.

 

[victor3ranger]

Just like mentioned before. you will need to check the fusible links carefully or with a voltmeter,ohm meter or test light. The outer coating may still be intact and the core is burnt thru. I also had things on the 12 volt side that were drawing power and killing the front battery only. Check carefully. I always go for any modifications that were done and see if they are drawing current when the key is off. A bad alternator can also cause a dead battery. I never had it happen but I seen it on new cab chassis units. We had several start fire while sitting parked and burn 10 to the ground over night. GM did a recall on that model year. It was a defective alternator issue. sevaral thousand units needed the updated alternators installed. Good Luck and I with you Happy New Year.

Is there a way to test to see if one of the alternators went bad without starting the truck?

I am not good with electrical stuff at all so this is something that has me concerned.

 

[cpf240]

Another thing that can happen is that the switch for the black out drive light gets bumped, and the drive light stays on. It is very hard to see in the daytime, and not all that easy to see at night either. There is also a relay in that drive light circuit that stays energized until the black out drive light switch is toggled off.

As for the alts, you could pull them and take them to an auto electric shop and have them tested. Could also try disconnecting the wires from the back of the alts, be sure not to let them short on anything, and see if the drain stops.

 

[Warthog]

You can also unplug the two prong exciter plug on the alternator.