Alternator changeout issues

[kendelrio]

Ok- so I swapped to the civvy alternator for my 5 ton that is offered to us by @74M35A2

Installed correctly (I believe) but am having issues.

I made sure when I installed the belt was tight, so that isn't the issue.

With the truck running, I am showing 29vdc from the positive post of the alternator. I did **not** check at the batteries (doom on me... booo!!!)

My alternator guage was in the red. I was told to expect it to read low, so that didn't seem like an issue.


I let the truck run about 5-10 minutes and went to shut down and the "start" switch didn't turn the truck off. I used the fuel shutoff to kill the truck, then when I tried to shut the batteries down, it wouldn't turn off the batteries.

I used an inline battery disconnect I had installed earlier this year to shut power off to the truck.

The new alternator only has a positive and negative post. I did not hook up the small black wires, one of which is a small ring terminal and the other is the military connector. They are isolated and electrical taped to keep them from touching anything. I did check ground with my multimeter and was showing 0.00 ohms of resistance, so that's good.

Anyone have any ideas? I have a message out to @74M35A2 explaining the issue and asking for a call, but does anyone have any idea what's going on?

 

[simp5782]

That is a draw red meaning something in your diodes in the pcb shorted to ground to protect the truck

 

[kendelrio]

That is a draw red meaning something in your diodes in the pcb shorted to ground to protect the truck

The only problem there is I took the diodes out when I rebuilt the PCB. I didn't have this issue before replacing the alternator.

Hmm... if I had accidentally hooked up backward, it should be REALLY anxious really quickly, right? As I stated, I had a good ground from the ground lug on the alternator and was showing over 200mb of resistance on the positive, so I should be good, right?

 

[simp5782]

Disconnect the power wire from the alternator and run an Independent wire from the alternator to the starter lug for the power. Delete the pcb from the charging system

If you couldn't shut if off with the start switch then you surely fried the pcb that is why it is on red I'm assuming the other powered gauges weren't working.

 

[kendelrio]

Disconnect the power wire from the alternator and run an Independent wire from the alternator to the starter lug for the power. Delete the pcb from the charging system

If you couldn't shut if off with the start switch then you surely fried the pcb that is why it is on red I'm assuming the other powered gauges weren't working.

I'll do that in the am. Too dark and cold to fool with it right now.

So if that's the issue, I'll show proper voltage at the batteries and guage, correct?

 

[simp5782]

I'll do that in the am. Too dark and cold to fool with it right now.

So if that's the issue, I'll show proper voltage at the batteries and guage, correct?

Yes but the gauge is always going to show lower power than what is being put out by the alternator due to the draw from the system and it reads power off of the dash gauge wiring. Which can be a volt or more lower

 

[simp5782]

Invest on one of these and mount it in your dash or somewhere. Much more reliable and easier to see when an issue happens over thr stock gauge

Amazon.com: DaierTek DC 12V 24V Car LED Display Voltmeter, 12 Volt 24 Volt Digital Voltage Meter Gauge Waterproof Mini Battery Monitor Indicator for Motorcycle Car Boat Marine with Blue LED : Automotive

Buy DaierTek DC 12V 24V Car LED Display Voltmeter, 12 Volt 24 Volt Digital Voltage Meter Gauge Waterproof Mini Battery Monitor Indicator for Motorcycle Car Boat Marine with Blue LED: Voltmeter - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[kendelrio]

Invest on one of these and mount it in your dash or somewhere. Much more reliable and easier to see when an issue happens over thr stock gauge

Amazon.com: DaierTek DC 12V 24V Car LED Display Voltmeter, 12 Volt 24 Volt Digital Voltage Meter Gauge Waterproof Mini Battery Monitor Indicator for Motorcycle Car Boat Marine with Blue LED : Automotive

Buy DaierTek DC 12V 24V Car LED Display Voltmeter, 12 Volt 24 Volt Digital Voltage Meter Gauge Waterproof Mini Battery Monitor Indicator for Motorcycle Car Boat Marine with Blue LED: Voltmeter - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Will do!

 

[kendelrio]

Ok... followup time...

After calling and chatting with @74M35A2 to ensure I wasn't messing up, I disconnected both wires from the alternator and connected a jumper cable from the "hot" of the alternator to the top post of my starter, removing the PCBs and rest of the truck from the equation.



I started the truck and checked my voltmeter on the dash and other instruments. It was reading low, just as expected.



I checked output to the battery and was getting 32.4vdc, so I knew the batteries were being charged.



At this point, I killed the truck and reconnected everything and restarted, no weird reading gs anywhere, 32.6vdc at the batteries. I checked the switches to see if they worked, AND THEY DID.... .

I restarted the truck and drove it to get fuel (about 30 minutes round trip) and got home, shut the truck down (all the switches worked again) and restarted and let it ide a while to charge the batteries some more then shut down for the day.

Weird... after short whipping the alternator to the starter, all of my issues went away.

I guess it had a gremlin it needed to get out.

Thanks to @74M35A2 and @Csm Davis for their help and expertise!

We truly have a great group of people here!

Oh... bonus.

My pop (who will be 80 this month) never had the opportunity to take a ride in my deuce. He was here today visiting and I had my step ladder out so I could climb in the engine bay and I asked him "Wanna take a ride?"

We got him in the cab and he rode with me to get fuel and back. He enjoyed the hell out of it!



He's a retired tugboat captain, and after I got up to speed he looked around and said "It's like sitting in the wheelhouse of a g*ddam towboat!"

 

[Guyfang]

You are turning into a Cracker Jack Mechanic!!

 

[kendelrio]

You are turning into a Cracker Jack Mechanic!!

Not by choice!!!

 

[Tow4]

Over 32 volts is a little high. I would expect 29.5 to about 30 max for a 24 volt system. Is that a 32 volt alternator?

 

[kendelrio]

Over 32 volts is a little high. I would expect 29.5 to about 30 max for a 24 volt system. Is that a 32 volt alternator?

I sent the pics to 74 and he said it was perfect.

 

[simp5782]

16 to 18v for every 12v of battery is a general rule

 

[kendelrio]

16 to 18v for every 12v of battery is a general rule

That's really good to know. Thank you!

 

[Tow4]

16 to 18v for every 12v of battery is a general rule

Actually, that is not true. In fact, I can't think of any 12 volt regulator set point that is more than about 14.8. A 24 volt alternator is simply double that or a little less.

I have a dual voltage 30SI in my M915A1 and it is 14 volts on the 12 volt side and 28 volts on the 24 volt side. Typical heavy duty 24 volt alternators like a 21SI, 22SI, 30SI etc. are about 28 volts. The reason being, you only need about 13.7 volts to maintain the charge of a 12 volt battery and avoid sulfation, any more and you start boiling the battery. Regular automotive alternators have a higher set point because of the way the vehicle is used. Multiple starts during the day means the battery has a shorter time to recover, higher voltage charges faster. Over the road trucks run all the time, so a quick recovery is not as important.

Over 30 volts on a 24 volt system is high. 32 volts is exceptionally high and that's the reason I asked if it's a 32 volt alternator that the op got by mistake. If the op wants to post the alternator model, I will look it up and tell him what he has.

 

[kendelrio]

Actually, that is not true. In fact, I can't think of any 12 volt regulator set point that is more than about 14.8. A 24 volt alternator is simply double that or a little less.

I have a dual voltage 30SI in my M915A1 and it is 14 volts on the 12 volt side and 28 volts on the 24 volt side. Typical heavy duty 24 volt alternators like a 21SI, 22SI, 30SI etc. are about 28 volts. The reason being, you only need about 13.7 volts to maintain the charge of a 12 volt battery and avoid sulfation, any more and you start boiling the battery. Regular automotive alternators have a higher set point because of the way the vehicle is used. Multiple starts during the day means the battery has a shorter time to recover, higher voltage charges faster. Over the road trucks run all the time, so a quick recovery is not as important.

Over 30 volts on a 24 volt system is high. 32 volts is exceptionally high and that's the reason I asked if it's a 32 volt alternator that the op got by mistake. If the op wants to post the alternator model, I will look it up and tell him what he has.

It's the one offered by @74M35A2 . He would have to tell you the model.

 

[74M35A2]

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.

 

[simp5782]

Actually, that is not true. In fact, I can't think of any 12 volt regulator set point that is more than about 14.8. A 24 volt alternator is simply double that or a little less.

I have a dual voltage 30SI in my M915A1 and it is 14 volts on the 12 volt side and 28 volts on the 24 volt side. Typical heavy duty 24 volt alternators like a 21SI, 22SI, 30SI etc. are about 28 volts. The reason being, you only need about 13.7 volts to maintain the charge of a 12 volt battery and avoid sulfation, any more and you start boiling the battery. Regular automotive alternators have a higher set point because of the way the vehicle is used. Multiple starts during the day means the battery has a shorter time to recover, higher voltage charges faster. Over the road trucks run all the time, so a quick recovery is not as important.

Over 30 volts on a 24 volt system is high. 32 volts is exceptionally high and that's the reason I asked if it's a 32 volt alternator that the op got by mistake. If the op wants to post the alternator model, I will look it up and tell him what he has.

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

 

[kendelrio]

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 figured out what happened with the guage. When I connected the alternator I accidentally grounded the hot on the casing.

The PCBs were rebuilt over a month ago.

The batteries were weak from me driving it to get it home when the old alternator crapped out.

The battery solenoid didn't work when I bought it so I installed a cutoff switch. The starter solenoid died about 2 months ago, which is why I rebuilt the whole PCB.

If all of this happened at once, yes. Big problems.

This all happened over the course of 10 months after the truck sat for 3 years.