General question about diesel engine electrics

[scottladdy]

Lot's of Charging System Questions ...

I have been studying the TM for the charging circuits and I have a couple of questions:

1. At the bottom/middle there is a diode. Because it shows wiring passing through the firewall harness plug it would seem that this is an external component to the alts. Is that true or is this a representation of the internal diode? Just by the logic of the circuit it would seem that the "exciter" circuit for the alts. is controlled by this diode and thus would be critical to its function.
a. If external, could it cause gen 1 to not charge?
b. If it can disrupt charging, where is the little guy physically on the truck and where do I get a replacement?
2. There is a relay "GENERATOR #2 RELAY" noted on the schematic on the right side just above the mid point.
a. The schematic shows no control circuitry for this. I would presume it is controlled by the ignition. Correct/incorrect?
i. Or, is the plug looking icon below it the wiring?
ii. If so, where do I find "Figure F-4" for the continuation of the circuit?
b. Could this relay affect the ability of the circuit to charge the battery(ies)?
c. If so, where is this relay physically and, where do I get a new one if its bad?
d. If there is a relay for GEN 1, is there a relay for GEN 2 that is noted somewhere else?
i. If there is no GEN 2 relay, why? What does it do for GEN 2 that GEN 1 does not need?

Thanks for your help!

WOW, lot's of questions.

Some simple answers, but please spend some time searching the forum. I think you will gain a much better understanding if you do.

Search for Gen2 relay (and search variants like Generator 2, alternator 2, etc) for your relay questions.
Search for Gen2 diode.

There is no relay for Gen1.

I know you are anxious to resolve your issues AND understand all of the details of the charging system. Please trust me in this. Take it systematically one step at a time. Before you know it, (but probably not soon enough ) you will start to understand the details. Just take your time and continue to study the TM's and the forum.

 

[bshupe]

Keep it simple. While eletrical systems can appear overwhelming, they are overall nothing more than pathways from one pole to another. Look at each pathway one step at a time. Test each branch and eliminate those that test OK. Keep track of your progress using the schematics as a visual aid.

I hope this helps ...

Thank you Sir, that is great info and encouragement. I did have the truck into my local ASE shop and they put the whole system under load and testing and could find nothing wrong. This was early in the process though so if the Alt is intermittent then it was unlikely they would have caught it. On the other hand it was a good sign that there is nothing else going on in the charge system.

I am waiting patiently for my parts (the PMs Im getting from people saying that its going to be a very long time is not helping ) and will be rebuilding both alts, doing the Doghead mod and replacing many other relays all at once. I am also getting up the nerve to take down and clean the harness plug at the firewall.

Thanks again!

 

[rtk]

NOT to be a PITA , Just a little advise for the future , the bit about removeing a battery cable WITH the engine RUNNING is a big NO NO , plus it a LITTLE out of date , who ever told you that was talking about GENERATOR equiped vehicles , last generator equipped vehicle was about 50 years ago . What ever else was wrong with your MV , might as well get TWO rebuilt alt's , because the DIODE's are probably fried or will fail shortly , electrical surges are VERY bad on ANY electrical parts , alt's , conputers , etc , as has been said before , you need to read the TM's before you start the repair , bob k

 

[bshupe]

WOW, lot's of questions.

Some simple answers, but please spend some time searching the forum. I think you will gain a much better understanding if you do.

Search for Gen2 relay (and search variants like Generator 2, alternator 2, etc) for your relay questions.
Search for Gen2 diode.

There is no relay for Gen1.

I know you are anxious to resolve your issues AND understand all of the details of the charging system. Please trust me in this. Take it systematically one step at a time. Before you know it, (but probably not soon enough ) you will start to understand the details. Just take your time and continue to study the TM's and the forum.

Thanks you again for taking time to read and reply. I do realize that is a pile of questions but at some level it is easier for me to work through a whole logical progression which puts the time burden on me and then people like you can skim and summaraize kicking out the false questions like the relay that doesnt exist which helps me narrow my effort significantly and quickly.

I will search for the other things you mentioned. I have searched extensively and read all the stickies etc. but havent gone too far in searching for variants of my search criteria. I will do that now.

Thanks again!

 

[bshupe]

NOT to be a PITA , Just a little advise for the future , the bit about removeing a battery cable WITH the engine RUNNING is a big NO NO , plus it a LITTLE out of date , who ever told you that was talking about GENERATOR equiped vehicles , last generator equipped vehicle was about 50 years ago . What ever else was wrong with your MV , might as well get TWO rebuilt alt's , because the DIODE's are probably fried or will fail shortly , electrical surges are VERY bad on ANY electrical parts , alt's , conputers , etc , as has been said before , you need to read the TM's before you start the repair , bob k

Well, perhaps by taking the cable off I pushed my alt over the edge and located my problem. lol

 

[MarcusOReallyus]

That is a very real possibility!

 

[scottladdy]

Well, perhaps by taking the cable off I pushed my alt over the edge and located my problem. lol

Marcus is correct. I would toss out any testing results you obtained before the cable removal. In other words, start at the beginning of the diagnostics again. But, you will be ever so much more proficient at it .

Keep plugging at it (pun intended). You'll resolve this issue.

 

[MarcusOReallyus]

I would toss out any testing results you obtained before the cable removal. In other words, start at the beginning of the diagnostics again.

That's good advice.


Otherwise, you'll confoozle yourself.

 

[bshupe]

Thanks for the additional support. I spent a few hours going through the system this last weekend cleaning contacts and checking connections etc. Now the GEN 2 light stays on full time. The operational symptoms have not changed but I think that going through everything has at least provided the truck with enough data to know that something is malfunctioning.

Just waiting for parts to come in the mail now and I will rebuild the alt.

On a side note: Ever since I have had the truck the dash turn indicators stay on and then blink off when the signals blink. I had also thought that my right front corner marker was burned out so I bought a replacement. When I got the lens off I discovered that the light was actually on it was just very dim. All contacts were very clean so I started tracing back and I discovered that the grounding tab in one of the front turn signals was broken off. For whatever reason this was causing there to be only 3.5v going to the corner marker. I temped a repair on the ground and all works great now including the dash indicators. I need to locate a new socket for that turn signal and replace the bad one. No luck so far finding a replacement. I also committed an ultimate sin and put the corner marker on top of my tire for safe keeping. Then I needed to move the truck for an unrelated matter and ran it over. On the prowl for a replacement corner marker housing and lens now.

 

[scottladdy]

Don't sweat the little mistakes. We all make them.

Turn signal issues you described are common. That ground terminal is a weak point. Sockets are available at multiple places, including RockAuto, LMC and NAPA. 1984 K30 pickup. Side markers too.

Your doing great with this. You'll be coaching the next person with electrical issues soon!

 

[bshupe]

Blushing....

 

[MarcusOReallyus]

Excellent work, bshupe!



Here's one to tuck away for future reference: Bad or partial grounds will cause some REALLY weird pull-your-hair-out symptoms.

 

[scottladdy]

... Bad or partial grounds will cause some REALLY weird pull-your-hair-out symptoms.

I guess that's why I'm bald? (ROFL)

 

[Tplane37]

Well, my search lead me here, and didn't have the answer I was looking for, but while reading, I figured I could offer some input here as well given that I JUST went through having to replace 3/4 of my starting/charging system on my 6.2L...

The OP and I have something in common... proficient with gas burners, semi-proficient with these diesels. With that said, just like on the gas burners, the starting AND charging system are one loop. Here's a difference that I found, the glow plug relay and system is part of the starting/charging system on these trucks (obviously a difference from the gas burners). At least on the 12V side of the loop, the alternator is pretty much the same as a 70's small block or big block Chevy, as is the wiring on the starter solenoid.

My first check would be wiring, including and especially the main battery cable going from the battery to the starter, look closely near anywhere it passes through the frame and near any exhaust. This is not a fused cable, and if it is grounded out, it can reek havoc on the entire system. The guy I got my truck from replaced the starter before I got it, come to find out the cable was to close to the manifold and melted the insulation, then grounded to the block, but I had to really hunt for the bad spot. Long and short, when this cable finally welded itself to the block, it took out my starter, two main (12V side) batteries, alternator, and some of the alternator wiring.

Look at the wiring on the alternators, not just for bare spots, but sharp "kinks" from how the wire are routed. Wires can break if they are kinked to tightly, but from the outside of the wire, everything will look fine while the wire can actually be broke inside the insulation... look closely where anything is kinked or pulled tight. Example: I bought a reman alternator, when I go to put it in, I find that the casing is clocked wrong and would cause the wires to kink and stretch tight in order to install it. A typical back yard mechanic would say "Everything still hooks up, and it works after its together, its fine." But this would have led to failure down the road. Result: I had to re-clock an alternator right off the shelf.

It sounds like you have some knowledge on the gas burners, and the starting/charging system on these 6.2L's is very similar to the mid-late 70's GM's, so use the PROPER knowledge you have learned from them, and you should be fine. There are a couple improvements I have seen on this site that you may want to do (doghead conversion for example). But you should spend the extra time and money on making sure your wiring is perfect, because if it ain't, nothing else you do on the electrical system will help!

 

[donalloy1]

Become real happy with a descent Volt Ohm Meter! You will learn much about vehicle electrical condition. Without that in your Tool Kit you will be blind. Just my .02.

 

[bshupe]

UPDATE: I finally had time to rebuild both alts and get them both installed again. Everything seems to have gone smoothly. I am now getting 12.8v on the front battery and 14.9 on the rear with the truck running. This is a significant improvement over my starting point but Im not quite there yet.

Everything in the rebuild process went by the numbers as far as I could tell. I was very diligent to keep all my parts organized and I didnt have any suspicions along the way of any errors or other problems other than one thing. On the drivers side alt, I accidentally got some of the new bearing grease on one of the new brushes. I cleaned them up real well so I dont think that would be an issue.

For one reason or another the passenger side alt is and always has been extremely difficult to get the belt tight. In my rebuild process I used a media blaster I had access to to clean up the case, fan and pulley etc. so even if the belt was a little loose it would turn the alt right now with how coarse the texture is. Brand new belts etc.

Im thrilled and very, very thankful for all the help I have had here getting this problem resolved. Im half way there and confident that I will be able to figure out the rest of it.

Thoughts, ideas and further guidance is most welcome. I did purchase a second set of rebuild parts (two full sets and two essentials sets) so if I need to tear one down again I can I guess. I would hate to burn that back up set since CUCV Electric is not shipping anything anymore. Lets agree that going right to rebuilding that one again is not our first troubleshooting measure.

Thanks!

 

[scottladdy]

Swap them if they are both isolated ground, the alternators that is. See if your issue follows the alt.

Voltage is regulated by changing the flow of electricity through the rotor, moderating it as the regulator sees changes in the line voltage. Not sure that greasing up your brushes would have affected that, but it is a possibility.

A new brush set is cheap - http://aspwholesale.com/index.php?act=viewProd&productId=100

Did you verify that the "hard parts" were OK when you rebuilt? Stator and rotor?

 

[bshupe]

Thanks scottladdy. I am going to try going back to stage one of the troubleshooting guide and see if I can ferret out any new problems. If I cant find anything then i will try the alt swap idea. I thought they were both isolated ground? How can I know? The only difference I saw between them was a condenser on the back of one and not the other.

Thanks for the link, I will keep that in mind as a replacement for what I have if needs be.

I dont know what I would do to check the hard parts. I did inspect them to see if there was any obvious damage and I put the meter from each of the taps to the case to see if there was any shorts. Is there something else I should have done?

Thanks!

 

[bshupe]

Charging problem solved!

After going back to basics with rebuilt gens installed I discovered that I was not getting the dash light for gen 1. This matched my condition of having 14+ on the rear and standing voltage on the front battery. I decided to check the lamps again just in case something happened in the interim. The Gen 1 lamp was not lighting with the key I pulled the Gen 1 lamp and it was good. This stumped me..... I swapped the Gen 1 and Gen 2 lamps in the panel and the non-op lamp followed. I started checking further and discovered that the lamp holder was not making a good connection to the lamp. I cleaned that up, reinstalled and turned the key. Bright illumination on Gen 1/2 and 14+ on both batteries.

Long road to an abrupt end but Im elated that things are working properly again.

Thanks for everyones help. Hopefully anyone following this post now or reading it in the future will take heed and check all these little details like I did not.

 

[MarcusOReallyus]