At my wit's end, please help

[Stocker]

Originally Posted by HO455

I would like to verify some of the facts here. First off are you running an alternator and regulator set like pictured below?

This alternator

And this regulator

Now the time line.
Several months back you added new fans and relays to operate them as well a a relay for the compressor clutch. Shortly after that your fusible link failed.

Then several weeks ago you installed a new alternator. And shortly afterwards you had several wires melt down. You said you changed the alternator as it was noisy. The new alternator was an 80 amp unit instead of the factory 62 amp unit shown above. At this time you problems getting the charging system to operate which you solved by swapping several regulators before going back to the old one and adjusting it. The new 80 amp alternator was damaged when the wires melted? It was replaced with another 80 amp alternator?

That's close but a bit out of order, I'll try to set it straight.

The old OEM alternator was noisy and I replaced it with a new 80A unit. At the same time, I added the fans. Shortly after that, the system overcharged and melted wires from the alternator to the regulator. The alternator was thought to be shorted internally so we replaced it with a new identical 80A unit and repaired the melted wiring. System was still overcharging and new regulators didn't fix it. At this point, the old regulator was re-installed and adjusted, and things seemed normal.

Several days later the fusible link blew. I was in traffic and failed to notice if the ammeter showed an excessively high rate of charge. I had been running A/C at the time and after re-attaching the remains of the fusible link, I made it home (well over an hour) without using A/C, just in case that was the problem.

I have since replaced the fusible link and added a relay for the compressor. Still dealing with a too-high rate of charge, which is where we are now.

You have installed a voltmeter and disconnected your amp meter?

No, still running the OEM ammeter.

Firedemon's link to madelectrical will help explain the difference between 1 and 3 wire systems in a coherent manner. That will give you the knowledge to decide which way to go if you are going to change to a newer internal regulated system.

Yes, I have been reading Madelectrical's site. Wealth of information there, for sure.
I have decided to get a 3-wire, 12SI, 94A internally regulated alternator. If I have trouble finding a 94A unit, I'll try for a 100A -- they seem to be fairly common.

[Stocker]

Originally Posted by Andy4639

The wiring is simple enough.

If you do this upgrade take the time and strip the wiring harness from the voltage regulator back to the red wire going to the alternator.

Take the small red wire from the external voltage regulator and install it on terminal #2 on the new alternator.

Take the small brown wire and install it on terminal #1.
Put the big red wire back on the new alternator and your done.

What about the blue wire and the white wire on the external regulator? Pretty sure they go to the 2 terminals on the existing alternator now. Will they just not be used with the new internally regulated alternator?

[Andy4639]

Correct. If you leave all that wiring at the regulator you jumper them.

If you strip them out of the harness just run the wires to the alternator.

[Stocker]

Originally Posted by Andy4639

Correct. If you leave all that wiring at the regulator you jumper them.

So I can retain the blue & white wires to the alternator..... simply splice white to brown (after removing them from the regulator, of course) and splice blue to red. Correct?

It may seem like I'm over-thinking this but I'm out of my comfort zone and do not want to screw it up.

[HO455]

I'm just trying to help you understand why and what happened. Your trucks stock charging system is the 37 amp system. The 62 amp factory alternators look like the ones in the photos I attached. They also have the different regulators. Plus there are additional wiring terminals on the core support near the regulator (like the one the fusible link connects to). I have not been able to locate a complete 62 amp harness to verify all the wire sizes but it appears GM used the 37 amp harness and added some extra conductors to allow the system to change at 62 amps without issues.
When you changed to the 80 amp alternator you more than doubled the alternators ability to charge. I am assuming that you did not increase the size of the wiring as you made no mention of that. I believe the meltdown of the wiring was caused by too much current flowing through the factory wiring. This compounded by any less than perfect connections meant the wires heated up until the insulation melted and something shorted. At this point is when the regulator went to full charge and you noticed that things had gone amiss.
In a properly engineered system the alternator can go to full charge for extended periods with no harm to the wiring of the vehicle. The battery is usually what fails as the water is boiled out of it until the plates overheat, warp and short the cell out. Sometimes leading to a battery explosion.
Not knowing how your new fans are wired in I am going to put forward a couple of theories as to why your fusible link failed. First is that the new fans are being powered through the fusible link and it wasn't able to carry them and the rest of the trucks load.
If they are not being powered through the fusible link then it is possible that your new alternator and it's regulator were not putting out enough voltage just prior to the failure. Lower voltage means higher amps.
Another option is the fusible link was damaged during the first failure and it was no longer able to carry its rated amperage.
Good luck on your resurrection of the charging system. Keep in mind your wire sizing as you upgrade to the increased amperage. The best part of this is once your done you shouldn't have to look at it for 100,000 miles or so.

[Stocker]

I appreciate any input I can get.... it all helps.

My original alternator was a 61A (maybe 62A?) Still, an 80A can put out more current -- but isn't it supposed to put out whatever the load calls for? In other words, it's not going to pour out 80 amps all the time, only the amount asked for by the truck. That's my understanding, though I may be wrong.

You are correct that I did not increase any wire sizes. I do not know which wires, specifically, would need to be beefed up. Can you offer any advice about that?

The fans are powered by a relay wired to the junction block on the fender -- effectively the + batt post -- not through the fusibile link.

[HO455]

First off I apologize somehow I got the idea your truck was a 67 thus the tangent off on the other alternator styles. The wires to be upsized would be the alternator output wire (red 12 guage on 1/4-20 bolt on the back of the alternator. And the battery charging wire (red 12 guage wire at junction block next to battery). I recommend you look at the first link for a good explanation of what wire is which and what size to go to and why. The quick answer is change the battery charging wire to a 10 guage and the alternator output wire to an 8 guage if your going for the 94 plus amperage alternator.
If you look at their Chevy diagram and compare it to a 67-72 C10 wiring diagram (2nd link) it is pretty easy to understand what they are talking about as it applies to our trucks. Trucks went away from the horn relay wiring they talk about on pre71 years earlier than cars did, but they didn't go to charging the battery through the starter in 71 like the cars did.

http://www.madelectrical.com/electri...evymain2.shtml

http://outintheshop.com/faq/wiring/wiring.htm

[Stocker]

Originally Posted by Andy4639

Here it is.
12SI, 94 amp, at 9:00 (AC-DELCO # 321-269, Lester #7294-9)
Tell the auto parts counter person that “The alternator is for a 1985 Buick Riviera, 5.0L (307Y engine), with Heavy Duty options and Air Conditioning.”

https://www.oreillyauto.com/shop/b/c...amp+alternator

It is on order, should be here Tuesday morning. Thanks Andy!

[Stocker]

Originally Posted by HO455

The wires to be upsized would be the alternator output wire (red 12 guage on 1/4-20 bolt on the back of the alternator. And the battery charging wire (red 12 guage wire at junction block next to battery). I recommend you look at the first link for a good explanation of what wire is which and what size to go to and why. The quick answer is change the battery charging wire to a 10 guage and the alternator output wire to an 8 guage if your going for the 94 plus amperage alternator.
If you look at their Chevy diagram and compare it to a 67-72 C10 wiring diagram (2nd link) it is pretty easy to understand what they are talking about as it applies to our trucks. Trucks went away from the horn relay wiring they talk about on pre71 years earlier than cars did, but they didn't go to charging the battery through the starter in 71 like the cars did.

http://www.madelectrical.com/electri...evymain2.shtml

http://outintheshop.com/faq/wiring/wiring.htm

Thank you! I just glanced at the first link for right now, will do more reading when I have time. But it looks like that shows exactly what I need to do.

[Andy4639]

Originally Posted by Andy4639

Correct. If you leave all that wiring at the regulator you jumper them.

If you strip them out of the harness just run the wires to the alternator.

Ok if you leave the harness in place just like it is now you use the top picture and jumper the wires at the external v regulator.
If you want to do away with all that and make it a little more neater under the hood use the bottom picture. They do the same thing just have less wires ran to the radiator support then over to the alternator.

[special-K]

Electrical is my weak point. I do have an understanding of the particular functions of most things electrical on these trucks through experience, though. I just don't have a full understanding to be the one giving advise. I am an advise taker in this area.

I have never experienced an overcharging system, yet I feel your issue is similar or the same as one I had in my old blue & white K20. I kept smelling rotten eggs and I never hauled eggs in it. Never saw a bird nest under the hood (at least not near anything real hot). It seemed to be coming from under the hood. I noticed the battery was warm enough to cook an egg, but no eggs in sight. It was a new optima marine battery. IIRC, I got to my old shop and the starter wouldn't crank. The purple(?) wire didn't look good so I went with new from the fuse block. Fixed that problem but still the rotten egg smell. I went with an later internal regulator alternator and the smell ended. I never considered that a one wire set-up. It used the two wire plug on the alternator and harness and eliminated the white(?) wire to the voltage regulator. Everything was still there if I every wanted to go back to original. It was really easy and straight forward. I hate the smell of rotten eggs. I'm glad I didn't get any on me or my truck. That could hurt.

* Spoda be sumwut silly story based on actual experience

[Stocker]

Originally Posted by Andy4639

Ok if you leave the harness in place just like it is now you use the top picture and jumper the wires at the external v regulator.
If you want to do away with all that and make it a little more neater under the hood use the bottom picture. They do the same thing just have less wires ran to the radiator support then over to the alternator.

A closer inspection revealed that the two wires to the alternator were damaged in the original meltdown and were replaced by my mechanic. So they are already spliced & taped up (and wrong color to boot ) and I will be replacing them with new wiring per the bottom picture.

Tim, I think we're pretty much on the same page when it comes to electrical stuff. I'm okay with the basics, but it doesn't take much complication to throw me for a loop. And I always envision things going 'poof' in a cloud of smoke....

[VetteVet]

Originally Posted by Stocker

A closer inspection revealed that the two wires to the alternator were damaged in the original meltdown and were replaced by my mechanic. So they are already spliced & taped up (and wrong color to boot ) and I will be replacing them with new wiring per the bottom picture.

Tim, I think we're pretty much on the same page when it comes to electrical stuff. I'm okay with the basics, but it doesn't take much complication to throw me for a loop. And I always envision things going 'poof' in a cloud of smoke....

As is often the case, we see some details that did not come out in the early descriptions that may be a clue to why a problem exists. If your mechanic replaced the blue and white wires it is possible that he may have crossed them up or that they are touching each other which would result in full fielding the alternator and causing the overcharge you have experience.This may have been caused by the original fusible link failure which was explained by HO455 . The wiring meltdown was most likely caused by a direct short in the wiring, rather than pulling too many amps, although full charge through the alternator will cause it to get very hot and fail shortly. The noisy alternator was probably the front bearing that takes all the load of the belts especially if the belts are too tight.

One thing not mentioned, have you experienced a battery drain? If the blue and white wires were crossed or touching that would cause a drain on the battery or if the battery plates have warped they will short the battery internally (again per HO455).

I don't think an 80 amp alternator or even a 100 amp is related to your problem as the alternator will only output enough amps to run the loads and charge the battery. It is true that too many amps on too small of a wire will cause melting insulation. This explains the key switch plug-ins and the need for relays. The stock truck has a relay for the AC fan and compressor or should have which I noted that your mechanic noted, so I would hope you have rectified that.

The link I posted above is very clear on how to convert to the SI series or even the CS which are better yet. I hope you have read it.

Lastly you have gotten some great advice and help in this thread.

[Stocker]

Trying to stay on top of the details but I always have doubts....

In the original meltdown, the truck had been running fine, then suddenly started pegging the ammeter, then everything went dead. The mechanic said the alternator had an internal short which caused the meltdown.

I have not experienced a battery drain throughout all of this.

*the alternator will only output enough amps to run the loads and charge the battery* that's always been my understanding too.... I went with a higher rated replacement alternator only because of the additional current draw of the fans. I am in the process of upgrading the wiring based on advise in this thread.

Yes, as I posted above, I ran the compressor wire through a relay. The fans were initially wired through a relay.

I have read a few links on converting to an SI series alternator. I have ordered a 94A 12SI internally regulated alternator and it should be here tomorrow.

I agree completely, I have gotten great advise & help in this thread, and I appreciate it very much.

As to my current progress today, I have replaced the 12ga red wire from the fusibile link to the point where all the red wires join. It is now a 10 ga. wire. I need to get a length of 8ga to run from that point (don't know what to call it) to the lug on the alternator. Then extend the brown and red wires from the old regulator to the terminals on the alternator.

[Stocker]

Originally Posted by Andy4639

The wiring is simple enough.

If you do this upgrade take the time and strip the wiring harness from the voltage regulator back to the red wire going to the alternator.

Take the small red wire from the external voltage regulator and install it on terminal #2 on the new alternator.

Take the small brown wire and install it on terminal #1.
Put the big red wire back on the new alternator and your done.

Doing this now, I stripped the wiring harness and extended the small brown wire. I'm ready to extend the small red wire but it's not exactly small -- it's 12 ga. There is no "small red wire" on the old regulator, just that 12 ga red wire. I guess that's OK and I can just splice a 16 ga red wire from it to the #2 terminal.


Edit: All wiring is now completed except for placing terminal ends and lug which I will do tomorrow after bolting in the new alternator. Very glad to see light at the end of the tunnel. Keepin my fingers crossed that everything works as it should. Can't thank y'all enough for the help & encouragement.

[Andy4639]

The red wire from the V-R it's the only one that goes to it.

I guess you figured it out!

[Ironangel]

Make sure all your ground straps are in place with clean tight connections. Spinning up 18 volts seems unusually high? That got me to wondering what the pulley diameters were between alternators, sometimes that makes a difference. I have a chrome 100amp one wire alt. on my BB truck, no problems in 3 years. I have an internally regulated alt. with the blue and white wires in place on the SB daily driver, no problems there either. I did make my own ground straps and added an extra strap from the block to frame and frame to inner fender insuring that rinky dink factory strap at the back of the motor wasn't getting over worked with a degraded connection from the valve cover to the firewall. One of the reasons I drive a 72 Chevy is there are no computers to present problems my 60 year old mind cant cypher. Tim, that rotten egg smell happens to me once in awhile, usually sumpthin I ate. Good luck

[Stocker]

I never have checked / reinforced my ground straps -- guess that would be a good project one of these days. In 41 years, I never had electrical problems until installing that 80A externally regulated alternator. That's when things started to go south. I think it speaks volumes for the goodness of the original design and hardware of these trucks. Disclaimer, I replaced a bendix drive on the starter many years ago. That's it, still the original starter and until now, the original alternator. Not bad at all. EDIT: Ironangel, you mentioned pulley diameters -- they have all been the same at 2 1/2".

Oh by the way Good News everyone! The new internally regulated alternator is on and seems to be working perfectly! It's outputting 14.5 volts at idle, and drops to just under 13 with A/C on (and sloooww idle, not sure just how slow). If it stays like this I will be one very happy camper!

I want to thank everyone again. I never could have fixed this without you. Board members here are some of the best anywhere!

[Steeveedee]

Good news! Alternator charging at idle should be 13.5 Volts minimum in order to push the electrons back into the battery. The 14.5 Volts is a good number for when the engine speed comes up. Look into what your idle speed is, since if you spend a lot of time idling, the battery can get discharged too much.

[Stocker]

Luckily I don't spend much time idling, but I'll check the idle RPM anyway just so I will know. The RPM is fine with A/C off, but goes down a fair amount when the compressor engages, and the draw from the fans might have a slight impact too. Should have checked idle speed today but I was too busy celebrating that the new alternator actually worked!

[Andy4639]

Glad it worked out and seems to be doing it's job for you.
At idle with ac on and in gear you should try for 650 RPM's min.
Main thing is make sure the lights and other accessories don't flicker are deem at idle.

[VetteVet]

Congratulations on the fix. It proves that if you stay with it you can solve most of the electrical problems on our trucks with the help of the guys on this forum.

It's been an interesting thread to say the least and I hope it helps a lot of the viewers.
One comment I would like to add is pertaining to the last post about idle charging being lower. Even the SI alternators are prone to this, and that's why I usually recommend going straight to the CS 130 or CS 144 style. They put out more charge at idle than the SI when a load is heavy at idle. They are just as easy to convert, are way more plentiful, and good used units are cheap.

[Stocker]

Originally Posted by Andy4639

At idle with ac on and in gear you should try for 650 RPM's min.
Main thing is make sure the lights and other accessories don't flicker are deem at idle.

Results of this morning's tests (readings are estimates taken with my old Sun Super Tach II and a crappy little digital multimeter).

Fast idle, choke on:
AC off, 1000 rpm, 14.67v
AC on, 750 rpm, 14.58v
AC on, in gear, 650 rpm, 14.30v

Engine warm, choke off:
AC off, 750 rpm, 14.56v
AC on, 600 rpm, 13.23v
AC on, in gear, 550 rpm, 12.40v

Voltage reading is steady with AC off, fluctuates a few tenths with AC on.
Headlamps dim slightly (nothing flickers) at idle when AC is turned on. Frankly, at this point I'm not concerned about it.

Side note: The LED bulb in my dome lamp chose this exact moment to flicker and then die. I'm thinking just great, that's what I need is more electrical problems. Turns out it was a failed bulb, and I had one (standard, not LED) on hand.

[Andy4639]

Originally Posted by Stocker

Results of this morning's tests (readings are estimates taken with my old Sun Super Tach II and a crappy little digital multimeter).

Fast idle, choke on:
AC off, 1000 rpm, 14.67v
AC on, 750 rpm, 14.58v
AC on, in gear, 650 rpm, 14.30v

Engine warm, choke off:
AC off, 750 rpm, 14.56v
AC on, 600 rpm, 13.23v
AC on, in gear, 550 rpm, 12.40v

Voltage reading is steady with AC off, fluctuates a few tenths with AC on.
Headlamps dim slightly (nothing flickers) at idle when AC is turned on. Frankly, at this point I'm not concerned about it.

Side note: The LED bulb in my dome lamp chose this exact moment to flicker and then die. I'm thinking just great, that's what I need is more electrical problems. Turns out it was a failed bulb, and I had one (standard, not LED) on hand.

You should idle up with the motor warm no choke on to around 650 in gear maybe 600 just depends on your self really. With the choke on it's going to idle pretty high which is what it's for to warm it up in the winter time.

[Stocker]

Originally Posted by Andy4639

You should idle up with the motor warm no choke on to around 650 in gear maybe 600 just depends on your self really. With the choke on it's going to idle pretty high which is what it's for to warm it up in the winter time.

Done. 650 rpm idling in neutral w/AC on, drops to 600 in gear w/AC. Neutral w/AC off idles at 1000 rpm which seems high to me but I can live with it. I can always adjust it back down a tad if it bothers me.