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Alternator question (and may a stupid one)


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Hey everyone, I hope all is well.

 

I currently have a Bosch alternator and even with the WT mod I am experiencing high AC ripple.  I plan to replace the alternator and am wondering if I can replace it with a Denso unit as they seem to be more plentiful than the Bosch units.

 

I also plan to keep my stock alternator and rebuild it with a new rectifier, bearings and brushes.  Has anyone rebuilt their Bosch alternator?  I'm curious if it is easy to do.  I have found a replacement rectifier online so they are available.

 

Thanks and I hope everyone has a happy Thanksgiving.

 

L8tr

d

 

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Just put a denso in and forget about rebuilding your Bosch. You can even put a slightly higher amp 160? one from Durango I believe.

I rebuild my Bosch it's not too bad. You'll need more than just a rectifier, brushes and armature will need to be changed also along with bearings that are pressed on. 

Honestly if you get a genuine denso should last a long time, that's why I don't see a point of rebuilding unless  you want something to tinker with or money is tight.

denso has a power stud in different location but everything still bolts on just fine.

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1 hour ago, Dieselfuture said:

Just put a denso in and forget about rebuilding your Bosch. You can even put a slightly higher amp 160? one from Durango I believe.

I rebuild my Bosch it's not too bad. You'll need more than just a rectifier, brushes and armature will need to be changed also along with bearings that are pressed on. 

Honestly if you get a genuine denso should last a long time, that's why I don't see a point of rebuilding unless  you want something to tinker with or money is tight.

denso has a power stud in different location but everything still bolts on just fine.

Yup... just updated the alternator part listing.

 

 

 

 

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I guess different opinions will vary on brands, but I’ve never rebuilt my Bosch, it’s been on the truck since new and got about 350k on it, still going strong and low ac noise, Ive always thought the Bosch was the most robust out of the two, If mine ever goes go out I wouldn’t bother with a rebuild kit or some auto store replacement but just go with a nations and hopefully be the last time I would have to deal with it,

 

@SilverMoose have you checked all your grounds or replaced your cables recently and the W-T ground mod, those could contribute to high AC noise alone rather than the alternator it’s self 

 

 

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My second Original alternator just shorted out again. First one was the original ND, original to the truck at 222,000 roughly. Six months later an original Bosch from the other truck with about 30,000 shorted out when I used the grids and then the seat heaters about 7 minutes apart. I saw the 150 amp fuse stud holding the cable, on the battery side of the fuse, glowing bright white the next day and never melted the fuse. Weird. I took the fuse out and don't need one IMHO.

 

Now I'm having rebuilds bench tested for AC ripple and get the Lifetime replacement....:thumb1: I will become the fastest alternator slinger in the west....:gun:

Edited by JAG1
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8 hours ago, JAG1 said:

My second Original alternator just shorted out again. First one was the original ND, original to the truck at 222,000 roughly. Six months later an original Bosch from the other truck with about 30,000 shorted out when I used the grids and then the seat heaters about 7 minutes apart. I saw the 150 amp fuse stud holding the cable, on the battery side of the fuse, glowing bright white the next day and never melted the fuse. Weird. I took the fuse out and don't need one IMHO.

 

Now I'm having rebuilds bench tested for AC ripple and get the Lifetime replacement....:thumb1: I will become the fastest alternator slinger in the west....:gun:

sum beach!!!

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11 hours ago, JAG1 said:

I used the grids and then the seat heaters about 7 minutes apart.

Considering the amp draw of the starter, I feel like this is just a coincidence. The alternator shouldn't be able to put out enough juice to smoke (or nearly smoke) the fuse. Either the fuse was bad, the alternator was bad, or both.

 

"WWW-T D?" What would W-T do?

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I know about the why of having a fuse or breaker, but why didn't the fuse blow instead of glowing the stud bright white. Something wrong there with a stud an inch from the fuse and the shrink tube is melting and stud lights up like a light bulb yet the fuse did not melt. Can someone explain that for me.?

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10 hours ago, LorenS said:

Considering the amp draw of the starter, I feel like this is just a coincidence. The alternator shouldn't be able to put out enough juice to smoke (or nearly smoke) the fuse. Either the fuse was bad, the alternator was bad, or both.

 

"WWW-T D?" What would W-T do?

 

No that not what is for again...The fuse or circuit breaker is not for overcharging alternator. It to stop the circuit flow if thew alternator shorts out.

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Thanks for all the suggestions.  I need to digest them all and and determine what my best approach will be.  Nations alternator on top of the list.  I need to check all the connections first.

 

Have a great Thanksgiving!

 

L8tr

d

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55 minutes ago, JAG1 said:

Yep, mine shorted but the fuse is still intact :shrug: I don't know what to think.

 

Your case the battery shorted out and overheated the alternator. Hence why the alternator was hot, and the fuse connection was hot. Still in all the alternator is only 136 Amps so it will never charge any more than that period even with a dead short. That fuse will never blow. 

 

Now if the diodes shorted to ground, like you mention in the PM with @W-T yes it does cover the shorted stator and shorted to ground diode. But it does not protect the armature which burns up the PCM voltage regulator circuit. 

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22 hours ago, JAG1 said:

when I used the grids and then the seat heaters about 7 minutes apart. I saw the 150 amp fuse stud holding the cable, on the battery side of the fuse, glowing bright white the next day and never melted the fuse. Weird.

 

1 hour ago, JAG1 said:

I know about the why of having a fuse or breaker, but why didn't the fuse blow instead of glowing the stud bright white. Something wrong there with a stud an inch from the fuse and the shrink tube is melting and stud lights up like a light bulb yet the fuse did not melt. Can someone explain that for me.?

 

It would be interesting to see a photo of that fuse after that event occurred.  What you have described is indicative of a poor electrical connection at a precise location, the fuse stud.  It would also explain why the nearby fuse didn't break the circuit.  Here is a possible scenario:

 

Truck electrical system is consuming 60 amps.  Poor connection at stud causes a 6 volt voltage drop at at the connection while alternator is flowing 60 amps (less than 1/2 alternator capacity) through the circuit.  If a voltage drop test would be performed during the event, one might see 18 volts on the alternator side of the connection and 12 volts on the battery side of the connection.  This would be a voltage drop of 6 volts while flowing 60 amps.  In your case both numbers easily could have been higher.

         

     60 amps x 6 volts = 360 watts of power at a very precise poor connection easily equals a glowing stud.  Kind of like the glowing tip of a 300 watt soldering gun when not contacting any work.

 

A very similar experience happened to my brother-in-law a few years ago.  He had Les Schwab install a battery isolator and a new auxiliary battery in the engine compartment of his truck.  The setup was for his slide-in truck camper.  We all went camping - us in our camper, them in theirs.  After several days of camping at one site, we left for to go elsewhere.  At our first stop along the way, my brother-in-law says that he was sold a bad battery because it blew up just after he left the campground.  We raised the hood to take a look.  Sure enough part of the top and side of the battery was missing.  But what wasn't missing was evidence.  The battery cable eye that was still clamped with a wing nut to the positive battery post was severely discolored by heat along with burned and melted cable insulation in the immediate vicinity.  Not a bad battery, but a glowing connection that ignited the hydrogen gases from a rapidly charging battery that was discharged at the previous campground.  One good reason not to use wing nuts for battery connections.  The point is that everything was working as it should, but a poor connection created a serious problem and a safety hazard. 

 

For all of the above reasons I do not rely on the physical appearance of electrical connections with high amperage circuits.  One needs to know if the electrical continuity is good at a given connection.  The only way to know that for sure is to perform a voltage drop test while the circuit is under a load.  @Mopar1973Manprovides an excellent article in how to perform this test.  

 

- John

 

 

 

 

 

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6 minutes ago, Tractorman said:

For all of the above reasons I do not rely on the physical appearance of electrical connections with high amperage circuits.  One needs to know if the electrical continuity is good at a given connection.  The only way to know that for sure is to perform a voltage drop test while the circuit is under a load.  @Mopar1973Manprovides an excellent article in how to perform this test. 

 

Bingo. I've done that already with ground cable and positive cables on my own trucks. One of the few reason I'm getting 9 to 11 years out of my batteries because the charging system 99% efficient. Then add in that I've reduced my electrical loads with LED lights and HID headlights so no the diodes stay cooler and alternator temps are down as well. 

 

This why I challenge the "ground jumper" between batteries be even adding that same jumper using jumper cables there is no change in voltage drop to the block period. Before adding I've got 3mV (0.003 volt)  drop between block and the either battery. Add jumper cables to both battery grounds still measure 3mV (0.003 volts). Voltage drop test is way I test for cable resistance or loss. Anything over 0.2 Volts is a fail for sure. 3mV (0.003 volt) loss is not even on the radar as a problem. 

 

For some of these older truck that have been abused and let the terminals corrode, oxidize, etc. Then if you measure 0.2 volt drop on any cable regardling the charge circuit or main battery cables its a fail without thinking. I would REPLACE any cables at that point that don't meet the mark. DO NOT ADD extra grounds or paralell cables to fix a bad cable. Fix the bad cable first. Then retest again. 

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2 hours ago, Mopar1973Man said:

if the alternator shorts out

I consider shorting out to be "alternator bad", and still has nothing to do with heated seats or grid heaters.

You seem to have agreed with me yesterday, though perhaps I could've phrased it better.


"Not good if the diodes happen to short to ground for what ever reason. (Poof! up in smoke). Why I still got that 150A circuit breaker."

 

And today!
"Still in all the alternator is only 136 Amps so it will never charge any more than that period even with a dead short. That fuse will never blow."

Edited by LorenS
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Alternator could be hook to a shorted battery and still won't blow during normal run. Fuse is 140 Amps and the alternator is 136 Amp Wide Open Throttle. Hence why the grid heater come on demand 195 amp (both elements) and alternator does not blow the fuse or trip the breaker. 

 

Now say your front end collision and the alternator snapped off the mount slammed into the block that would be a dead short on the charge lead now the battery will out power the fuse and blow, not the alternator. Being the batteries total are 1500 amps (or more) with both batteries (stock CCA). See the battery cause the fuse to blow not the alternator. Being the alternator on high idle still can reach 136 Amp with the grid heaters but doesn't blow the fuse or breaker. Not suppose too...

 

Technically the grid heater are a dead short of sorts being that it draws 195 amps (both elements) at 14.0 volts that is 0.071 ohms. Yeah that's a in a nutshell is a controlled short that creates roughly 400*F to 500*F temps in the manifold. 

Edited by Mopar1973Man
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