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I like so many of us go through alternators. I was doing some research as to stop this problem and ran across a rectifier with Avalanche diodes. What little I can find about them is that is what the newer cars are using. From what I have found these will clamp the voltage spike caused by large current  things like when the grid heaters turn off. What I have not found was the specs for the voltage that they clamp to or if they will help with the ripple that causes our problems. This is call out to anybody out there with more knowledge then me or better search results if these would be a good choice. 

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They are actually avalanche rated. Which means the makers actually bothered to measure it. The it being how repetitive and severe the voltage spikes can be in the normally non conducting state and still the device can survive. Basically  means more robust and bragging rights for the maker. Most non avalanche rated devices just have an absolute spec and thou shall not exceed it, but you may get lucky a few times.

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They way that it was explained to me was in automotive use during a heavy current draw ( like our grid heaters ) when the draw is turned off the voltage regulator doesn't react fast enough and causes a high voltage spike that can cause damage to electronics. Being we have 2 batteries this might not be a problem but as these trucks age and connections oxidize  I can see it becoming a problem. The only way that it was described to me was it worked like a giant zener diode to clamp down any voltage above their rating. So far I havent found if this is true or at what  voltage that is. One site stated that the breakdown voltage was 24 volts tho 36 volts and at that point the magic smoke has already escaped on a 12 volt system. This little adventure started about a week age when I checked my ripple voltage and noticed it was just above 40mv. When I went to get a new one and had them test it the test machine said it was good but when they printed out the results the values were far above a failed point. I took the new unit to 3 other parts houses and even with different looking testers none gave a print out that made sense and they all said passed. These were testers that I used 2 years ago with a lot of onfo and all voltage levels for pass and fail. All I can think of is that so many failed out of the box they up dated the software to stop the problem. I ended up talking to 4 custom alternator rebuilders and the " avalanche diodes " came up and I wondered if it was something that might be good thing.

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I am still using my original Bosch alternator.  Two sets of brushes, one bearing set, and still original diodes.  Still passed the AC voltage test last time I checked.  One thing I have done different is that I rewired control of the grid heaters to a momentary switch inside the cab.  I choose when to use them and  they never operate after the engine starts, so there is minimal impact on the alternator.  I did the mod when the truck was new - the current odometer reading is 344,000 miles.  Just another way of looking at alternator problems.

 

- John

 

 

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9 hours ago, Tractorman said:

I choose when to use them and  they never operate after the engine starts, so there is minimal impact on the alternator.

 

I just unhook the grid heater positive lead. From April to October my grid heaters are unhooked. Then from October to April I hook them back up for the winter season. MPG fooler prevents the pre heat of the grid heater but doesn't help with post heat. 

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I have owned my truck for just over 7 years now and I do store it from Nov. to April. It is started only about 4 times during the winter just to keep the juices flowing ( i don't need to but it makes me feel good ). When it is removed from storage I disconnect the grid heaters and they might be connected when I take a trip in Oct. if the temp gets low enough to need them. My truck is not a daily driver and I only put about 10k miles on it a year including a 4k mile trip in Oct. so use of the grid heaters is minimal. When it was purchased it had a alternator from a small rebuilder that lasted me 5 years but I don't know when it was installed. The next one that I installed lasted 2 years! To me this is a problem that needs to be looked into ( I am disabled and I am doing the W_T mod at this time). Because I hit the road for up to 4 weeks during my trip I need it to be rock solid reliable and easily repaired by me when on the road. After talking to custom rebuilers I think that I should not reinstall a stock denso and from what I have read maybe install a bosch unit. Because I do travel in some desolate areas I need something that I can get fairly quickly so custom is out of the question in my mind. The more I think about it and being I really have not heard much bad about them I think the connectors will get changed and a bosch will be used. If anybody thinks this is a bad idea please sound off.

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7 hours ago, Nekkedbob said:

The more I think about it and being I really have not heard much bad about them I think the connectors will get changed and a bosch will be used. If anybody thinks this is a bad idea please sound off.

 

I don't think it is a bad idea.  My view is a bit one-sided because my only experience is with a Bosch alternator.  I ran that alternator for 215,000 miles before I replaced the brushes and bearings.  There was no performance issue - I just did it for maintenance.  And, since my grid heaters have not post-cycled since the truck was new, this could be why my alternator has been very reliable.

 

However, when I had about 120,000 miles on the truck, I asked a very reputable auto-electric repair shop about replacing the brushes and bearings on my alternator.  He asked which one do I have - a Bosch or a Denso?  I told him Bosch and he said that he would be happy to change them out, but the brushes are about at at there half-life and the bearings at about one-third life.  He recommended that I just keep running it for awhile, which I did.

 

- John

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All I can say is I’m still running my original Bosch and now at 340000 mi.I’ve never done anything to it and it’s never exceeded recommended A/C ripple either, I also never have disconnected grids as they get used quite frequently here in Colorado even in the summer mornings 40 degree or below is fairly normal. I have done the w-t ground mod just for good measure and becouse it just makes since to an even electrically challenged individual like myself. 

With that said, If my alternator was to give up tomorrow I’m not sure a Bosch replacement would give the same performance being its just a gamble as with the quality of everything else these days, However if Im in that situation I would definitely look into the nations alternator being that they have a robust reputation, they are a bit pricey but if you’ve had to buy two or three alternators you could have paid for one. Just buy once and cry ? once is the way I look at it.

 

I would think along the lines of a good alternator keeping your electrical system up to par is key 

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I looked into nations and a couple other ones and they all say I can just have them overnite the parts but where I stay when on the road doesn't have a address and I don't think they will deliver " down dirt road X 40 miles on right ". I have had times that I unloaded my off-road/on-road motorcycle and made a 180 mile round trip to a parts house to get on the road again. I am also wondering what I might have to change to make a bosch work other then the field connector. During my time on the forums I dont recall any posts about bosch problems but I can see some people that had problems with their alternator and just got a rebuilt unit and never knew what brand it was.

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