CUCV alternator symptoms M1009

[lightbar91]

please help have M1009. Gen 2 light is on went running. Did the test 24.5 volts key on and off small red wire .
12.5 volts key on. no volts with key off
??? ???

battery 1 12.5volts

battery 2 12.73 volts

looking inthe TM what am I missing

 

[Warthog]

Help us help you. We need more info.

Read the CUCV Alternator sticky. It has many tests to perform. They all came from the TMs.

Do both GEN lights come on when you turn the key to RUN?

In you first sentence, where were you getting the 12.5v reading from?

Is you truck wiring bone stock or has it been modified? While you gave some readings they are a little confussing.

Remove the 2 pin plug from the alternators and check the voltages. Fill in the blanks.

GEN1 - drivers side
key OFF
small red wire - xx.x volts
small brown wire - xx.x volts
Key ON
small red wire - xx.x volts
small brown wire - xx.x volts

GEN2 - passenger side
key OFF
small red wire - xx.x volts
small brown wire - xx.x volts
Key ON
small red wire - xx.x volts
small brown wire - xx.x volts

How do the plugs look? very dirty? corroaded? Clean? You might buy a can of Electrical Contact Cleaner at you local auto parts store and clean them. If they are in really bad shape you may need to replace them.

Plug the wires back in.



Battery Voltage - check at the battery terminals of each battery. Dont use the truck for ground.
truck off
front - xx.x V
rear - xx.x V
truck running
front - xx.x V
rear xx.x V

How long have you had the M1009 and have you ever had the alternators rebuilt?

 

[lightbar91]

Do both GEN lights come on when you turn the key to RUN?
YES

In you first sentence, where were you getting the 12.5v reading from?
Brown wire Gen2 from 2 wire plug

Is you truck wiring bone stock or has it been modified?
I do not know TM wiring looks right.

Remove the 2 pin plug from the alternators and check the voltages. Fill in the blanks.

GEN1 - drivers side
key OFF
small red wire – 12.73 volts
small brown wire - 0 volts
Key ON
small red wire – 12.73 volts
small brown wire – 12.73 volts

GEN2 - passenger side
key OFF
small red wire – 25.53 volts
small brown wire - 0 volts
Key ON
small red wire - 25.53 volts
small brown wire – starts at 0 V go up to 12.5 volts and stays volts

How do the plugs look?
New replaced them
Replaced all battery contacts and wire also
Plug the wires back in.



Battery Voltage - check at the battery terminals of each battery. Dont use the truck for ground.
truck off
front – 12.73 V
rear – 12.51 V
truck running
front – 14.4 V
rear 12.51 V

How long have you had the M1009
1 year
have you ever had the alternators rebuilt?
No tested GEN1 in truck 14.43 V
Tested Gen2 auto parts store 14.53 V
Also lamp for gen2 one side 25.5 V and other side 12.5 V lamp is good
And tested relay also good

 

[Warthog]

Thanks, GEN2 is not receiving enough voltage to excite. I will pull up the wiring diagrams and post the parts to start checking.

Everything else looks good.

 

[Warthog]

The circuit for GEN2 is working, but isn't passing the required 24v thru it. It is the small brown wire you checked. We need to find out why.

Follow post #92 of this thread:

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

It has the path that current flows for GEN2. I'm not reposting the pictures and diagram

Check the very bottom fuse first. Remove it, clean it or replace it. And then check the GEN2 relay

First thing to do is check the very bottom 24v fuse. If it is bad GEN2 won't work. And the GEN2 relay must be working.

Current flow is : fuse, GEN2 bulb, relay, diode, firewall and then the alternator plug.

The brown wire comes thru the firewall and is part of the large wire bundle and works its way around the back of the engine and then to the alternator. The thick RED circle is the GEN2 terminal (ignore the thin red circle - it is a left over from another issue)

I'm sure you have read the first few pages of the troubleshooting section of the TM 9-2320-289-20 tech manual. It tells you how to read the diagrams and what all the wire labels and diagrams mean.

 

[lightbar91]

ok got 25.5 volts to brown wire Gen2

Remove the 2 pin plug from the alternators and check the voltages. Fill in the blanks.

GEN1 - drivers side
key OFF
small red wire – 12.73 volts
small brown wire - 0 volts
Key ON
small red wire – 12.73 volts
small brown wire – 12.73 volts

GEN2 - passenger side
key OFF
small red wire – 25.53 volts
small brown wire - 0 volts
Key ON
small red wire - 25.53 volts
small brown wire – 25.53 volts

How do the plugs look?
New replaced them
Replaced all battery contacts and wire also
Plug the wires back in.



Battery Voltage - check at the battery terminals of each battery. Dont use the truck for ground.
truck off
front – 12.73 V
rear – 12.51 V
truck running
front – 14.4 V
rear 12.51 V

till the light is on what would be the next step

 

[lightbar91]

surry
ok got 25.5 volts to brown wire Gen2

Remove the 2 pin plug from the alternators and check the voltages. Fill in the blanks.

GEN1 - drivers side
key OFF
small red wire – 12.73 volts
small brown wire - 0 volts
Key ON
small red wire – 12.73 volts
small brown wire – 12.73 volts

GEN2 - passenger side
key OFF
small red wire – 25.53 volts
small brown wire - 0 volts
Key ON
small red wire - 25.53 volts
small brown wire – 25.53 volts

How do the plugs look?
New replaced them
Replaced all battery contacts and wire also
Plug the wires back in.



Battery Voltage - check at the battery terminals of each battery. Dont use the truck for ground.
truck off
front – 12.73 V
rear – 12.51 V
truck running
front – 14.4 V
rear 12.51 V

still the light is on for Gen2.
what would be the next step
p.s. Tested Gen2 auto parts store 14.53 V

 

[Warthog]

Time to take the alternator off for testing. May need rebuilding.

 

[lightbar91]

Is the drivers side Gen1 the same as Gen2 and are they both 12 volts alts??

 

[cpf240]

Yes, they are both the same, isolated ground alternators. Well, assuming no one has swapped them out with something else. It is not uncommon to use a standard alternator on the drivers side. Only the passenger side alternator *MUST* be an isolated ground unit.

 

[lightbar91]

How would i find out if it is a isolated ground alt??

 

[Warthog]

Look at the model number cast into the housing or look for the extra wire going from the alternator ground post to the engine block. It is a larger black wire.

There have been hundreds of post talking about the "isolated ground" alternators, many with pictures.

Islolated ground alternators have the internal electronics separated from the case. Instead of using the case for grounding, there is an extra terminal that grounds the unit.

 

[lightbar91]

Ok gen 2 is working after you start the truck and give it some fuel it starts.
battery rear 14.24 volts
battery front 14.32 volts
both 18.94 volts
so is this working right??

 

[lightbar91]

new info
gen 2 is working after you start the truck and give it some fuel it starts.
battery rear 14.24 volts
battery front 14.32 volts
both 28.94 volts
so is this working right??​

 

[Warthog]

Those are good readings. How did you fix it?

 

[lightbar91]

All I did was replace the brown, red, wire plug on the top gen 2
The brown wire was worn through and shorting on the motor
so I replace it.
drove into work and found gen 2 lamp was off and the 24 volt meter in truck was in the green.

 

[lightbar91]

Thank you for all the help
I thing I will replace the warning lamps in the instrument cluster with instrument cluster gauges with a tach.
do you know what Hz gen 1 is, and where the Tach mod is located in the truck??

 

[addinquir]

Gen 2 24volt bottom fuse, where is it located?

Where is that fuse? my Gen2 light will not go on and the bulb is good, the rear battery reads 12.7 volts. Am I missing something? I replaced with 2 separate alternators and got the same results. anybody have any solution?
Maybe Warthog?

The circuit for GEN2 is working, but isn't passing the required 24v thru it. It is the small brown wire you checked. We need to find out why.

Follow post #92 of this thread:

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

It has the path that current flows for GEN2. I'm not reposting the pictures and diagram

Check the very bottom fuse first. Remove it, clean it or replace it. And then check the GEN2 relay

 

[addinquir]

Hi guys,
I sent a message to Warthog.
My problem is that when I turn on the key the gen2 light does not go on and I dont know if gen 2 is charging.
I pulled the 2 wire plug off the gen2 alternator and with key off, I get 24v on the red wire and 0 volts on the brown / white striped wire.
With the key on, I get 24v again on the red wire and again, 0 volts on the brown / white striped wire.
I checked the 10amp fuse next to the flasher on the bottom of the fusebox and its good.
On another note, on the Gen1 plug I get 12v on the red wire and 0 volts on the brown / white striped wire with the key off but
With the key on for gen1 I get 12 v on the red wire and only 7.3 volts on the brown wire.
Note, gen 1 light does go on when key is on and after starting, gen light goes out. Never had a problem with gen1 and front battery.
There you have my symptoms and I have no clue why I get zippo on gen2 brown wire with key on. But more interestingly, gen 1 is fine with inly 7.3 volts on the brown wire.
Any thoughts from anyone would be great.
( rear battery does need help with a boost to start truck probably due to this gen2 problem)

 

[cpf240]

Perhaps the GEN 2 relay under the dash is bad / missing?