Alternator changeout issues

[kendelrio]

Also noting how dead his batteries may have been it isn't unheard of for that. I assumed that was his output as soon as he started the truck

Yes. The batteries were so low they only clicked when I tried to start.

 

[Jbulach]

…This is exactly why I quit advertising alternator kits a long time ago. You are then immediately on the hook for anything electrically wrong with everybody’s 30 year old trucks, from headlights to taillights…

Go figure… the water heater in my garage bathroom has been putting out too many amps ever since I put the alternator I got from you on the shelf next to it.

 

[simp5782]

Go figure… the water heater in my garage bathroom has been putting out too many amps ever since I put the alternator I got from you on the shelf next to it.

I'd Blame him for it too

 

[74M35A2]

Hooking stuff up reverse polarity doesn’t help, but at least you were honest about it. Not sure what is damaged or not.

Check the alternator running voltage again both hot and cold later once you have things in better shape. At idle and raised RPM as well. The regulator may or may not be damaged, which could explain the 32v reading. No big deal if it needs to be replaced, it is a simple and low cost, easy to obtain part. I can even do it for you if it needs and you send it to me.

 

[74M35A2]

Go figure… the water heater in my garage bathroom has been putting out too many amps ever since I put the alternator I got from you on the shelf next to it.

LOVE YOU LONG TIME BRO !!!!

OP never blamed, I just magically get sucked into dam near everything.

 

[kendelrio]

Hooking stuff up reverse polarity doesn’t help, but at least you were honest about it. Not sure what is damaged or not.

Check the alternator running voltage again both hot and cold later once you have things in better shape. At idle and raised RPM as well. The regulator may or may not be damaged, which could explain the 32v reading. No big deal if it needs to be replaced, it is a simple and low cost, easy to obtain part. I can even do it for you if it needs and you send it to me.

I'm going good be driving the truck for about an hour and a half tomorrow and I'll run the checks when I get home. That will put a good charge on them, I can check output voltages etc and go from there.

 

[kendelrio]

And if anything is still wonky at that time I'll let you know, and as far as being honest, that's the only way I can be.

I'm not **positive** (see what I did there?) that I grounded the hot, but thats honestly the only thing I can think that would have caused the issue I had. If it's wonky or messed up, I'll be glad to pay to have it repaired. I'm a firm believer in being accountable for your actions.

 

[Tow4]

I was referring to your dash gauges working with the dash battery switch turning on/off as being perfect, as you said it formerly did not do that.

There is a lot more going on with this truck than just the alternator. Owner said he had to drive it on the stock over-charging alternator for a while, so you won’t know what that damaged by doing so. Tough spot, no easy way to disconnect it temporarily during a drive and reconnect later on the drive. Belt drives water pump as well.

Then a report of the dash switches not controlling the engine correctly.

Then a report of PCB rebuild without reinstalling the high voltage flyback protection diodes.

Then the truck operating properly if the alternator is connecting directly to battery and not using the vehicle harness. Dash switches did not work, but then magically did the next time.

Then an observation of the dash voltmeter in the low yellow even though the charging system seems to be working and even a bit high (explained below).

Then a report that the batteries are very weak.

The new replacement alternators have a temperature compensated voltage regulator. The colder the ambient air around the alternator is, the higher the voltage setpoint is. After start, as it runs and warms up, the regulated voltage typically reduces. This is because they want to recharge the batteries after start as fast as possible, without boiling the acid in them. So, a colder regulator has a higher setpoint, a warmer one will be lower. This takes more than a few minutes of running to do so. Alternator itself has to be pretty warn.

There is more going on with this truck electrically than just the alternator replacement. The truck really needs a few hours spent on it diagnosing what is or went wrong, what got damaged, and fixing it. That really can’t be done over the internet, phone, or text. It needs to be done using the schematics, a meter, observations, electrical know-how, and climbing around the truck checking things. Roping in opinions of a bunch of different people and getting them fighting is not the way to do it. Connecting the alternator to the starter is OK, will work, and is how new trucks are wired. But that does not explain or correct the several other points observed and stated above, which are all outside of the alternator arena.

This is exactly why I quit advertising alternator kits a long time ago. You are then immediately on the hook for anything electrically wrong with everybody’s 30 year old trucks, from headlights to taillights. The alternator is $120, the Cummins upper bracket is $100, pulley $15, shipping is $40, lower brace and hardware is $10. $15 profit is just not worth it anymore.

People here want to be as helpful as we can, but nobody can actually fix it from states away. Different people will have different opinions and experiences, especially with electrical stuff that is not tangible. Simp has a lot of experience with these trucks and working on them, but Tow is actually correct in his charging voltage statements. 32v is a pinch too high for continuous warm running, but is OK for an open air cold start measurement. Take the truck for a long drive with the hood closed (more than 15 minutes), and remeasure once the alternator is warm to the touch. Get the batteries charged back up, get your low dash volt gauge reading correctly (ground issue?), get your dash switches working properly, get diodes back on your PCB solenoids. It should be lower than 32v running once warmed up.

I completely understand 74M35A2. Like you, I worked in the rotating electric field for many years. I've done or had my tech do many durability/destructive tests on different new alternator components. I never offered complete units because of the reasons you mention.

32v isn't too high for a cold start environment like Clint said. My delco with remote sense will kick it up there to that voltage if my truck gets drug down on a long winded cold start. I have a dual digital readout directly off the equalizer so it is pretty accurate.

Also noting how dead his batteries may have been it isn't unheard of for that. I assumed that was his output as soon as he started the truck

The regulator is not going to exceed the set point. Cold or hot does not matter, they are temperature compensated for hot under the hood temperatures. I could see the voltage being higher hot when read at the alternator with remote sensing, cold is not a problem. Either way, voltage at the battery should be the set point if using remote sense. The op was measuring the voltage at the battery. 32 volts at the battery is high.

If the batteries are dead, that will pull the voltage down. The alternator will not be able to over come the load at idle and the voltage at the batteries will be less than the set point. To get full output, the alternator is going to need to run far above idle speed. It's going to take awhile to get to the regulator set point at idle if the batteries are low.

If you have dead batteries, put them on a battery charger, alternators are not designed for that kind of load.

 

[74M35A2]

Some differing things here, but I have no problem politely bowing out. I was on my way out the door anyway.

OP, glad you have most of your stuff resolved.

 

[Guyfang]

You are doing good! Learning by doing. Keep it up.

 

[simp5782]

You are doing good! Learning by doing. Keep it up.

Till it turns into a Car B Q

 

[kendelrio]

Hooking stuff up reverse polarity doesn’t help, but at least you were honest about it. Not sure what is damaged or not.

Oh, I didn't hook it up backward... I think I may have touched the terminal of the positive side to the case while tightening it down. I think it twisted clockwise and the terminal was touching the case.

 

[74M35A2]

Oh, I didn't hook it up backward... I think I may have touched the terminal of the positive side to the case while tightening it down. I think it twisted clockwise and the terminal was touching the case.

Only half backwards then.

 

[Jbulach]

After shorting the alternator, you might want to at minimum check it and the PCB out before going on an 1-1/2hr drive.

24 volts and 2500 amps does amazing things!

 

[kendelrio]

After shorting the alternator, you might want to at minimum check it and the PCB out before going on an 1-1/2 drive.

24 volts and 2500 amps does amazing things!

Yeah, I've got the truck sitting on a nice slow 2a charge letting the batteries get nice and full before I fool with it.

 

[Guyfang]

Till it turns into a Car B Q

Oh yea of little faith!

 

[kendelrio]

Follow up to the follow up...

I broke the cardinal rule of troubleshooting electronics.

I didn't verify my test gear was accurate.

I was using my meter to test the voltage on my motorcycle battery and it was showing 15.7vdc.

After scratching my head, I swapped it to A/C and put it on my wall outlet. It showed 180VAC, which I knew was wrong.

Battery swap for a new one on my meter and the house was showing 121VAC, the motorcycle was showing 13.6 and at idle the batteries in the truck are now showing:



And at 1000rpm the alternator is showing:



I need to tighten the belt some more, but everything is reading right.

My apologies.

 

[charlesmann]

Id like to piggy back please.
Monday, i went on a short test drive to see if leaving the exhaust side on my svc brake chamber open at the tee made a difference on the dragging. I scanned my gauges about a mile from my house and noticed my charging gauge, with head and svc lights on, was sitting at the bottom of the yellow, but when turned head lights off, it moved to the middle of the yellow. I got hm and checked the output at the alt and at the batteries, and i was showing 24.5 volts at both. Today, i decided to check again and at both idle and 1800 rpm, i was getting about the same. I checked amp output at alt and it was at 8.04. Now, im not sure if i had my meter set properly for amps, but see attached pics and let me know if it operator error, or alt issue.

 

[kendelrio]

I believe you need to move your probe to the "Amp" (red) probe.


You should have a "high" or standard Amp port and a "low" Amp port. Wrong port and you blow a fuse.


Without seeing the entire face of the meter, I can't tell.

 

[Tow4]

Id like to piggy back please.
Monday, i went on a short test drive to see if leaving the exhaust side on my svc brake chamber open at the tee made a difference on the dragging. I scanned my gauges about a mile from my house and noticed my charging gauge, with head and svc lights on, was sitting at the bottom of the yellow, but when turned head lights off, it moved to the middle of the yellow. I got hm and checked the output at the alt and at the batteries, and i was showing 24.5 volts at both. Today, i decided to check again and at both idle and 1800 rpm, i was getting about the same. I checked amp output at alt and it was at 8.04. Now, im not sure if i had my meter set properly for amps, but see attached pics and let me know if it operator error, or alt issue.

Battery voltage is 12.7 for a fully charged 12 volt battery. X2 for 24 volt system or 25.4 for a 24 volt battery pack. Either you are measuring wrong or the alternator isn't working.