Gen 1 & 2 dash lights

[Sharecropper]

Let me make sure I understand this correctly. If either of the GEN dash bulbs burns out, the alternators will not charge?

 

[MarcusOReallyus]

Correct. It's a really stupid design.

 

[KI4FKW]

Yeah, odd thought for a design.

A - no light = alternator charging
B - no light = bulb burned out and alternator not charging

 

[MarcusOReallyus]

Yep.

Having an indicator is good. Making that indicator tell you two very different things by the same condition is very stupid.

Worse, making the function of a critical system dependent on that indicator is brain dead.

 

[Sharecropper]

Let me make sure I understand this correctly. If either of the GEN dash bulbs burns out, the alternators will not charge?

I started this thread because a couple weeks ago I pulled my M1028 out for its annual spin in the snow. After a day of fun, around dusk I headed back to the security and warmth of my facility, and noticed that my headlights were dim and my dash panel lights almost nondiscernable. The truck was running fine, but it seemed my batteries were draining. Neither of the GEN lights were on, so I pulled it into the shop for evaluation. It was after posting this thread and receiving replies that I figured my GEN 1 bulb had burned out, so I embarked on the process to replace it.

When I was younger I could reach the dash bulb sockets by laying on my back in the drivers floorboard, and reaching up around the steering column. But because of 2 back surgeries, 2 hip replacements and a knee replacement, it is easier for me to simply sit in the drivers seat and remove the instrument cluster. Easy enough, the most difficult part was getting the speedometer cable off. Once I got the cluster out and started to remove the dash bulb in the GEN 1 socket, I discovered the problem. It seems that a previous owner (National Guard motor pool) must have replaced the bulb before, and in doing so tore the copper loose from the circuit film. See photo below. When the bulb socket was twisted and snapped into position, it was barely touching the rippled-up copper. No telling how long it had been this way, as I have only driven the truck 2500 miles in 9 years. I did not want to leave the truck apart because it was still snowing and felt that I might actually need it to get home, so I decided to try to fix the issue. There was no way to get the rippled-up copper to lay back down and make contact with the bulb socket, so I rummaged around in my spare parts bin and found another old GM circuit film off a C60 truck. I took a sharp razor knife and cut off a piece of copper circuit in the same shape as the rippled-up section on my circuit film. I then used the razor knife to very carefully separate the copper from the film, and then used a Scotch-Brite pad to freshen-up both sides of the tiny piece of flat copper. I then used the razor knife to flatten-out the rippled-up copper on my original circuit sheet, and pulled the Scotch-Brite across it to freshen-up its face. I then applied a generous bead of dielectric grease on the rippled-up film, and then placed the new copper film on top of it. The grease held it in place until I could twist the bulb socket (with a new bulb) in place. I plugged the cluster back in and tuned the ignition switch to see if it worked and, Bingo! I placed my battery charger on the front battery, reinstalled the cluster, and now everything is back to normal.

This whole process made me realize just what a weak design this is. The tiny sliver of copper has the potential to stop my truck in its tracks. Thank goodness I caught it while I was still in town close to my shop. If it had happened 20 miles from the nearest road and without cell phone coverage, I may have been hiking out. I am hoping someone with more expertise than me can engineer a work-around for this design defect. I really believe this issue is just as important, or maybe even more important than the Doghead relay fix.

My circuit film repair was a temporary fix. I need to order a new circuit film. Does LMC offer the correct film?

Thanks.

 

[TGP (IL)]

Yes
Pt# 38-8036

http://www.lmctruck.com/icatalog/cc/full.aspx?Page=90

Tom

 

[cucvrus]

I spoke with the man at the alternator shop. He is going to build me an alternator that does not require the idiot light o light. I will report back. He claims it will be a plug and play. I have had issues with a few badly worn CUCV plow trucks that are going to get that fix applied to. I am tired of crawling under the dash in a storm and twisting bulbs and sockets. The system worked great for many years and some trucks I have they still work great. But this will be going into the shredder when the plowing duty is over. So I don't need to mess with it all the time. Just continue to use the gauge as the indicator of charge or dis charge. It always worked on everything else. Have a Great Day.

 

[Sharecropper]

I spoke with the man at the alternator shop. He is going to build me an alternator that does not require the idiot light o light. I will report back. He claims it will be a plug and play. I have had issues with a few badly worn CUCV plow trucks that are going to get that fix applied to. I am tired of crawling under the dash in a storm and twisting bulbs and sockets. The system worked great for many years and some trucks I have they still work great. But this will be going into the shredder when the plowing duty is over. So I don't need to mess with it all the time. Just continue to use the gauge as the indicator of charge or dis charge. It always worked on everything else. Have a Great Day.

Rick I would be interested in knowing how that can work. It is my understanding that the original design requirement for voltage to run through the GEN 1 & 2 bulbs is a system design, not an alternator design. I'm looking forward to your report.

 

[Keith_J]

I've added a combination digital volt/ammeter to the driver side alternator ground line, measuring voltage off the high side alternator. I have almost complete information on the charging system.

There are voltage regulators which will "turn on" by sensing the AC off the stator, meaning the engine is turning. Thus they do not need the lamp current (which is key switched, eliminating battery draw with engine off).

 

[MarcusOReallyus]

There was no way to get the rippled-up copper to lay back down and make contact with the bulb socket, so I rummaged around in my spare parts bin and found another old GM circuit film off a C60 truck. I took a sharp razor knife and cut off a piece of copper circuit in the same shape as the rippled-up section on my circuit film. I then used the razor knife to very carefully separate the copper from the film, and then used a Scotch-Brite pad to freshen-up both sides of the tiny piece of flat copper. I then used the razor knife to flatten-out the rippled-up copper on my original circuit sheet, and pulled the Scotch-Brite across it to freshen-up its face. I then applied a generous bead of dielectric grease on the rippled-up film, and then placed the new copper film on top of it. The grease held it in place until I could twist the bulb socket (with a new bulb) in place. I plugged the cluster back in and tuned the ignition switch to see if it worked and, Bingo! I placed my battery charger on the front battery, reinstalled the cluster, and now everything is back to normal.

Nice McGuyvering!

This whole process made me realize just what a weak design this is. The tiny sliver of copper has the potential to stop my truck in its tracks.

Yep. I don't know what craziness drove this nonsense, but I'm sure tight deadlines and low budget played a major role, and possibly some government stupidity, as well.

 

[doghead]

All that and, that's the way it was done 50+ years ago.

Time takes it's toll on everything, seen and unseen.

 

[MarcusOReallyus]

Time takes it's toll on everything, seen and unseen.

Yeah, just ask my joints!

 

[cucvmule]

Great Idea! Just a thought I wonder if spray copper coat would "glue in place" the strip and make contact also?

 

[MarcusOReallyus]

Hmmm. I'm not sure there's enough exposed copper for that to work. It's made to transfer heat, not electricity. Like "conductive grease" (which is not conductive), the metallic particles are probably encapsulated in the goo that makes the gasket, so I would guess it would not be useful as a conductor. Maybe as a glue. But, that's just a guess.

You are probably better off with something that is made for that purpose.

 

[DeadParrot]

The Gen light current also serves as the excite current for the alternator. It isn't a military thing, it is how GM alts worked in that time era. If your civilian GM vehicle has idiot lights, same thing. If it has an amp/volt gauge, then there was a resistor added that served the same function. IIRC, that resistor is internal to the Alt and probably what the alternator shop is adding to fix the issue.

In a pinch, you can just feed 12V to the excite pin on the Alt. The bulb/resistor is used to keep feedback current from powering the ignition coil on a gas vehicle when the key is turned to off.

Guessing that GM's thinking was the GEN bulb would last the life of the vehicle as it is only on during startup and designed to run below high brightness.

 

[cucvrus]

GM was right that the light would last the life of the vehicle.

With the average age at an all-time high of ​

11.4 years

, cars are on the road longer than ever before. This infographic shows how long cars may last and how you can increase your vehicle’s life expectancy. I see this as being a very accurate statement. Most of the vehicles in Pennsylvania with any average wear and tear and pretty well Kaput at 15-20 years. The new de-icing chemicals they are putting on the road are eating thru every part of the truck. I seen 2011 and 2012 pickups that had perforation thru the rocker panels and the bed sides. Rust never sleeps. I think the fact that the CUICV's sat around a lot on the military bases has extended the time they have lasted. But for the most part they will rust away just like any other vehicle. No vehicles are rust resistant. Road chemicals and salt water are the biggest contributors. Good Luck. Most of the plastics on the CUCV are dry and brittle. Replacement parts are not of the same quality as the new ones were. All you can do is fix it as you go with what ever you can source to keep it going and in running order. Many of the Genuine GM parts are parts built world wide. As long ago as 25 years I seen parts on new US built trucks that were made in China and Taiwan. I think electronics have come a long way since the CUCV's left GM Flint assembly. ​

 

[acthomp781]

I just had a similar issue. My Gen 1 light would only come on at start up at times, not every time. I chased it down to the bulb socket brass "clips" that the bulb sits in the socket were slightly corroded. A few seconds with a small file and now the system works again.

 

[Matt5]

This is all a troll right about the light? Have any of you ever been in a vehicle made in the last 20 years? Any of 1000000 sensors decides it does not like what it sees and it can shut your entire vehicle down... and you all are complaining about a light? Takes less time to screw with the light than it takes to remove the cab on a ford to START working on anything.

I mean hey a 20 year old volvo has a CEM that contains the relays for the headlights, when one fails, its a $1000 part vs a $4 relay but... oh man this light... dumbest thing ever...
Oh wait, take pretty much any new vehicle made at all... if it thinks anything is wrong it can and will derate...
Like really?
Or what about like, everything running over a common databus now... hey the radio (that works) has a fault... and your ass is on fire because the heated seats don't shut off...

Then again this thread has mr. keep it stock modding his alts so wow this is a unicorn for sure.

Like all that had to be done here is, run a wire ... the copper pads are dissipating heat... god that is too funny...

 

[MarcusOReallyus]

It's amazing how pre-teens these days love to throw around that word, "troll", without even knowing what it means. It's kind of a generic insult for them, I guess, so they don't have to actually think about the issue being discussed.

 

[Sharecropper]

This is all a troll right about the light? Have any of you ever been in a vehicle made in the last 20 years? Any of 1000000 sensors decides it does not like what it sees and it can shut your entire vehicle down... and you all are complaining about a light? Takes less time to screw with the light than it takes to remove the cab on a ford to START working on anything.

I mean hey a 20 year old volvo has a CEM that contains the relays for the headlights, when one fails, its a $1000 part vs a $4 relay but... oh man this light... dumbest thing ever...
Oh wait, take pretty much any new vehicle made at all... if it thinks anything is wrong it can and will derate...
Like really?
Or what about like, everything running over a common databus now... hey the radio (that works) has a fault... and your ass is on fire because the heated seats don't shut off...

Then again this thread has mr. keep it stock modding his alts so wow this is a unicorn for sure.

Like all that had to be done here is, run a wire ... the copper pads are dissipating heat... god that is too funny...

I sure hope a Moderator bans this guy.