M1009 How to check no power to left alternator?

[sheriff443]

Brothers, how do I check no power problem at drivers side alternator? Please help...706.970.9689 TIA

 

[Warthog]

First place I would start is the CUCV Helpful Threads sticky.

http://www.steelsoldiers.com/showthread.php?123199-CUCV-Helpful-Threads

There are some good threads to troubleshoot the alternators. One of them is:

http://www.steelsoldiers.com/showthread.php?54292-CUCV-alternator-symptoms-diagnosis-and-fix

And you can always follow the alternator troubleshooting section in the TM 9-2320-289-20 tech manual.

We need more info. Is the truck stock? Has the alternator ever been rebuilt? What is you knowledge level as far as electrical troubleshooting? Know how to read wiring diagrams?

 

[sheriff443]

alt. help

Thanks Mr. Warthog for the quick reply! I think the truck is stock except for Doghead relay mod.
Alternator looks to be rebuilt and has a tag: Triple Tested, Tech Support 800.854.0076. Don't have much experience at troubleshooting electrical problems, but can read wiring diagrams..

 

[sheriff443]

Sorry thumbs got in the way. 800.854.0076

 

[tim292stro]

Do you have a multimeter for measuring voltage?

 

[sheriff443]

Do you have a multimeter for measuring voltage?[/QUOTE


Tim, I have a digital ammeter. I replaced a bad bulb (Gen 1) in instrument cluster. Then proceeded to remove the flat plugs from both alternators to check volts. Alt.1 (left/drivers side) w/ignition key off: 12.5V. Alt.2=24.8V. No voltage at brown wires. When checking the volts on Alt.1, I found a loose terminal where the heavy red wire mounts that would not tighten. Upon removing the alternator the stud fell to the concrete floor and I heard the nut rattling inside the alt. case. It is going back to Auto-Zone as it has a lifetime warranty. I got a reading of 1.5V at the heavy red wire when truck was running, any ideas?

 

[tim292stro]

Your alternators are ([EDIT] absolutely should be!! [/EDIT]) isolated ground, if a stud was spinning it's probably because the nut inside was not tight - having that fall inside is a good way to have an electrical fire start... You should have two fat wires coming out of that alternator too - since it's isolated ground, it can't be grounded by bolting it to an engine like other alternators - it needs that second power wire to ground. IT also goes without saying that if you use a non-isolated alternator in the CUCV system and hook it up to 24V, it will go "poof", and let that magic smoke out that makes electronics work (you want to keep the smoke in ).

With the two wire connector unplugged your alternator should do nothing. The wire furthest from the positive output lug is the voltage regulator power supply, the one closest to the positive output lug is the idiot light wire. When you turn on your ignition, the switched positive supply for that alternator is provided to one side of an idiot light bulb - the wire from the other leg of the idiot light goes to that terminal on the alternator. The voltage regulator in the alternator has that wire connected to the field coil which charges the alternator's rotating assembly. If that charge should fail the idiot light would be grounded through the field coil and would light.

If you measure across your two fat wires at the alternator you should see ~12V for the lower (driver's side) alternator, and ~12V for the upper (passenger side) alternator. If you measure from the positive output of the lower alternator (driver's side) to a chassis point of the engine block you should read ~12V, the upper alternator (passenger side) should show ~24V. Once you've seen this, that means your power wires are probably good. If not, you have some new cables to make.

If you stick your meter probe into the two pin connector removed from the alternator with the key on, but the engine off - both pins should be 12V relative to the ground wire from the alternator you removed the plug from. If not, you have a control wiring problem. If you turn the key off, only one of those wires should be powered.

Can you take a picture and post it of the wiring for each of your alternators?

Others are going to ask: have you read the TM's? It's good advice, they have a lot of troubleshooting info in there.

 

[sheriff443]

Tim, thanks again for all the great content and expertise. I have been immersing myself in the TM's with any available free time. Tomorrow I will take pics. of alts. and wiring. I returned Alt. 1 (drivers side) to Auto-Zone as it has a lifetime warranty. They actually dropped $20. in price in the last 3.5 years! How strange? but fine with me, still same lifetime warranty...

Does the 8RED-2B (SXL) red wire coming off of the terminal on back of Gen.(Alt.) 1 go to a fuseable link at firewall?

 

[sheriff443]

Replaced Gen 1 today, voltage at terminal w/red wire was 55V when idling, Gen 2 (passenger side) was 19V !! Upon checking wiring further with 2 master mechanics, a fuseable link at the firewall was found to be the problem. The Lord knows I'm no mechanic by any means, He helps me! After pulling away the melted insulation and twisting the broken ends together and firing up the beast, all was well in GREEN land. She purrs like a Lion... 14V @ Alt 1 and 26V @ Alt 2 ! Thanks brothers...