Alternator diode heat

[Mopar1973Man]

20 minutes ago, NIsaacs said:

There is way more to an alternator than a diode. How much does it cost to keep rebuilding yours?

 

When it just the diodes that are failing the cost of the diodes. Never had brush failure yet. Then one case failure and one bearing failure. (OE alternator). The rest where all diodes failures last year 3 alternators during the winter time one only lasted only one month and diodes blew out. 

 

20 minutes ago, NIsaacs said:

Napa has a lifetime warrantee on theirs for $102.

I've burned up 5 of those. A couple did not even make it out of the store dead in the box. Ended up going to another store. Currently, I've got Autozone lifetime right now and it's holding up. Last winter when Installed this one I pulled the grid heater and it stopped the alternator failures for the rest of the winter. This last summer did the W-T ground wire mod.

 

Now, this winter I'm going back to using the grid heaters and seeing if I can figure this diode failure out. Eventually, the diodes will overheat and fail.

 

When you can fry diodes out of an alternator the only reason is high loads. The only thing with high loads is the grid heaters. Which I proved already if you leave the grid heater unplugged then the alternator failures stop. Like I've said in previous post why is my 1996 Dodge 1500 alternator which is 22 years old and never been replaced and OE yet still going? No high loads or grid heaters. 

 

I know Ibmobile is working on a grid heater switch that id Ca. EPA compliant where it does not throw codes.

Edited October 19, 2018 by Mopar1973Man

[NIsaacs]

I noticed in the battery thread you might have weak batteries. Maybe the alternator is doing all the work? I also noticed that your engine is spotless. Do you cover your alternator when you power wash it? My engine is dirty but it is happy 

[Mopar1973Man]

13 minutes ago, NIsaacs said:

I also noticed that your engine is spotless. Do you cover your alternator when you power wash it?

I typically wash the engine down when cool. I don't directly hit the alternator straight on with full 3,000 PSI. But no different than driving through a rainstorm or snowstorm where water is pulled through by the fan and splatters on the alternator. Like I've got 6 months of that coming of flooded highways and wet snowfall.

 

13 minutes ago, NIsaacs said:

I noticed in the battery thread you might have weak batteries.

Yeah that is true. Being they have been ran DEAD twice. They are not the 750 CCA rating no longer but are starting just fine for the time being. I'll check them with a volt meter today and see what the overnight draw is like. 

[NIsaacs]

I noticed that before my last set of batteries died that when I plug my dump trailer in to top off the battery, the charger was not shutting off like it should. It was back charging my truck batteries that were bad but still starting the truck fine. These trucks start so quick I think the batteries can be bad but still start. With the new batteries, the dump charger shuts off again like it should.

 

Sometimes we can't see the forest for the trees and a random comment can get us refocused. Just a thought, but maybe your grid heaters are just fine.  

[2000Ram2500]

11 hours ago, IBMobile said:

I'm waiting for it to be cold enough here for the final tests on it.   

 

I grew up out there it doesnt get that cold. Not yet anyways. I do remember it getting pretty cold around new years or closer to it though.

 

13 hours ago, Mopar1973Man said:

There grid heater technically is not grounded there it own body. The aluminum housing that holds the element. There is a single stud that passes out of the aluminum body and this stud is on the front side of the grid heater. Single lead looped around to the inside front mounting bolt. Being the gaskets between the manifold to the grid heater and the grid heater to the air horn there is no contact for ground. So to prevent arcing from weak ground this lead on the front is added to give a solid ground for the grid heaters. 

 

This is the ground for the grid heater.

 

The two studs on the back at the two power leads. 

 

So then technically the short wire at the front would be an auxiliary ground then for the simple fact it cant ground through gaskets. It would be pretty easy to spot corrosion at that point. But what about the lifetime the power side spent connected to the battery? It would be possible for the battery side of those wires before the fusible link to see some effects from battery acid.

[dripley]

My connection to the battery is questionable on mine. What cooper you can see at the connector is very discolored. Not sure how far this comtinues down the wire or if it is corrode. The wire at the connector is not corroded but definitely discolored. 

[2000Ram2500]

Same with mine very discolored and not corroded but that doesnt mean its impossible.

[Mopar1973Man]

@IBMobile

 

Grid heater measures out at 0.1 ohm cold after been heated and quickly checked its roughly 0.5 Ohms and sinks back to 0.1 ohms as it cools. 

 

As for alternator performance is capable of jumping right up to 14.5 volts right away as the grid heaters kick out. As for AC noise, I'm measuring 10mV AC WITHOUT grid heater running and 29mV AC WITH grid heater running. Still, the alternator is in excellent condition. Still very concerning to feel the amount of heat given off by the diodes. 

 

Battery at rest was 12.65 volts this morning. Batteries took a beating but still holding a good charge. After starting the alternator can bounce right up to 14.5 volts no problem. 

 

The only thing I've not done is find out the orange/black and the yellow/black wires and when they function. 

[2000Ram2500]

 

[Mopar1973Man]

[Tractorman]

4 hours ago, Mopar1973Man said:

Grid heater measures out at 0.1 ohm cold after been heated and quickly checked its roughly 0.5 Ohms and sinks back to 0.1 ohms as it cools.

 

I don’t think that a resistance test on a high amperage circuit will have much value, primarily because the resistance changes greatly as the element is heated.  Your test results kind of show that.  For example, using Ohm’s Law based on your tests, the following results would be true  if there is 12 volts available at the intake heater and the wiring is good condition:

Cold intake heater at 12 volts  / .1 ohm = 120 amps.  (A bit high, but in the ballpark)

Warm intake heater at 12 volts  /  .5 ohm = 24 amps.  (I don’t think this is accurate)

I think that a quality load tester with a clamp-on ammeter would get the results that you are looking for quickly.  You could load test each intake heater circuit individually with the engine off, and then with the engine running.  You could also test actual alternator output while grid heaters are cycling with or without high idle.

I think using above test procedure would be very informative and you would quickly know whether or not the air intake heaters are performing as they should.

This morning I performed a voltage drop test on the intake heater circuits.  I prefer voltage drop tests over just inspecting electrical connections.  Voltage drop tests tell you exactly what is going on with pinpoint accuracy because the test is being performed while the circuit is under its normal load.  Many times I have seen what appears to be a clean and tight electrical connection, but the connection fails the voltage drop test because it is a dirty connection “electrically”.

So, here is the information regarding my test.  My truck is an ’02 with just over 300,000 miles on the original Bosch alternator.  The intake heaters were modified to be operated manually by a momentary switch shortly after the truck was new.  Since I only use the intake heaters when needed (never after engine is started), the alternator has had an easy life.  At 215,000 miles as a maintenance procedure, I replaced only the brushes and bearings on the alternator.  The current batteries in my truck are Group 24, 890 CCA @ 32*, 725 CCA @ 0*.   The batteries are four months old.

I manually performed two 10 second heat cycles with engine off, then three  heat cycles with the engine running.  I allowed a brief recharge time between cycles.  I recorded the following readings in the last 5 seconds of the fourth and fifth heat cycle with engine running:

Voltage drop  = .6 volts from left positive battery post to each intake heater positive stud terminal.

Voltage drop = 11.0 volts from each intake heater positive stud to common intake heater negative stud terminal.

Voltage drop = .12 volts from common intake heater negative stud terminal to left negative battery post.

The average battery voltage remained at about 11.7 volts during the last 5 seconds of each test.  The sum of the voltage drops under load equals the average battery voltage under load within .02 of a volt.  The .6 volt drop in the first test represents each fusible link in the positive side of the circuit, so this voltage drop is expected.  The .12 volt drop in the third test represents a good ground circuit (should be under .2 volt drop.)  The 11.0 volt drop in the second test represents the electrical load – the actual work being done.

 

The voltage drop tests that I performed do not tell me the amperage draw of the intake heaters, but they do tell me that the condition of the wiring is good and the intake heaters are working.  I only posted the voltage drop testing information because I think is the best method for maintaining good electrical connections before problems occur.  One of the many benefits from using voltage drop testing is that any potential poor connection is never disturbed, but easily found during the test.  Voltage drop testing is a very powerful diagnostic tool for determining the quality of electrical connections, but the procedure is probably the least used and the most misunderstood.

- John

[2000Ram2500]

25 minutes ago, Tractorman said:

Cold intake heater at 12 volts  / .1 ohm = 120 amps.  (A bit high, but in the ballpark)

Warm intake heater at 12 volts  /  .5 ohm = 24 amps.  (I don’t think this is accurate)

 

Dividing by .5 is the same as multiplying by 2. Dividing by .1 is the same as multiplying by 10. (Im a nerd sorry..) which is quite the wide swing in amperage. If the 120 figure is close than that means its taking almost every amp the alternator puts out which would be quite the load on it. Ours are 136 i think right?

[Mopar1973Man]

If you did have 0.1 ohms and both elements are powered that would be 240 amp draw. Even at 0.1 ohm and single element at 120 amps is 25 over the mark. One element should be 95 amps which would be 0.126315789 ohms.

 

I can't explain it but a warm element has higher ohms. 

[Tractorman]

1 hour ago, Mopar1973Man said:

If you did have 0.1 ohms and both elements are powered that would be 240 amp draw. Even at 0.1 ohm and single element at 120 amps is 25 over the mark. One element should be 95 amps which would be 0.126315789 ohms.

 

I agree with your above statement.  The multi-meters that I use currently and in the past do not display a value lower than .1 ohm.  Will your multi-meter display a value lower than .1 ohm, such as .01 ohm?  If your meter is limited to measuring in tenths of an ohm (like mine), then theoretically the 95 amp element would be rounded down to .1 ohms.  If your meter can measure in one-hundredths of an ohm, then the 95 amp element would be rounded to .13 which would be a value that you can work with.

 

So, what I am trying to say is since the meters that I have worked with are limited to measuring within a tenth of an ohm, a .1 ohm reading could really be .08 ohms (150 amps), or .13 ohms (92.3 amps), for example.  Since the meter would round these numbers to .1, one could draw an incorrect conclusion about how much actual amperage draw there is.   This is why I don't use an ohmmeter to check for resistance on a high amperage circuit with the meters that I am familiar with.

 

I still think that using a quality charging system tester with a clamp style ammeter would give you the most accurate intake heater current draw in a real-life situation and also tell you which heaters are operating after the engine is running during post heat cycles.  Plus, you can check the output of the alternator during post heat cycles with or with out high idle.

 

I apologize now if I have made this topic more confusing than it should be.

 

- John

[dave110]

On 10/18/2018 at 11:07 PM, IBMobile said:

                     I thought they stuffed chicken in a casket.

It never ends.......................................

[ofelas]

A cost effective way to get a better alternator with 12 diodes & a 6 phase stator is the 160amp "Police package"  unit used on some early 2000's Durangos & LEO vehicles.

 

You'll need to swap it's 7 groove pulley with the 8 groove diesel pulley, and use the newer OEM style 2 prong field connector in place of the bolted on field terminal/power block.

 

With the higher idle of a Cummins, mine was right at around 122amps at idle, and the lower end of 180amps at max load.

 

[Mopar1973Man]

Still brings me back to why did my OEM alternator last 10 years without a single issue without modification or upgrading? What has changed to make the diodes overheat and fail? Upgrading alternator is not a solution its just another band-aid covering over the problem and not solve the actual problem that is causing the diode overheating.

[Haggar]

Mike,

 

I have been pondering this for a few days.  There is no true explanation for "why now".  The load of the grids doesn't go directly to the alternator.  It is buffered by the batteries.  Yes the alternator has to eventually recharge that, but it doesn't go bananas.  (or just as bananas as your starter which pulls more...)

 

What you/we might be seeing is the reduced quality of some of the electrical components.....  I am seeing it a lot in capacitors...  They just are not the quality that they used to be.   I am somewhat seeing it in resistors also.  They just won't carry their rated load for any extended period of time.  (though they used to...)    I don't know the manufacturing process for diodes.  But if the same manufacturing process and materials changes are similar in those to what has happened to capacitors and resistors, it might be this problem.

 

Just my thoughts, no proof (on the diodes anyway...  capacitors I can show you many examples...)

 

Hag

[Mopar1973Man]

I'm waiting for winter to set in full swing here and get cold. I've been watching the AC noise levels and waiting for it to rise. Since doing the W-T Ground wire mod is still very low at like 10mV AC and barely 29mV AC with the grid heater hitting. 

 

Still makes you think when I've got just the 1996 Dodge 1500 with the same style alternator with over 22 years of age and over 180k miles and never been replaced it still an OEM alternator.

 

What's different? Electrical loads... Like the diodes get rather hot to the touch just as the grid heater hits. As the grid heater shut off you can feel them cool down from what air movement the alternator can create.

 

Like I've got the Quadzilla set for a 170*F warm-up mode and 15-second delay so if the coolant is below 170*F and no moving for 15-seconds it jumps to 1,200 RPM. What I'm trying to figure out is reducing the diode heat. Once the grid heaters shut off the diodes cool right off. With the Quadzilla setup, this way helps because the alternator fan keeps the diodes cooler. Still a band-aid to the problem. If I disconnect the grid heater power supply outright the diodes never really get warm. Here I'm back to circling the grid heater again... 

[2000Ram2500]

As far as the load being on the battery yes it is but the pcm is in control of charging so im sure the second it sees a draw like that it ups the output of the alternator to cover the deficit. Otherwise it would run the batteries down pretty fast. And being that the alternator is at its max just about to power the heaters i can see why its getting hot.

 

Could it be a combination of things? Such as a combination of short cuts during manufacturing, the high load, the truck itself is aging. And what about the fact its in a very cold environment also. Going from hot to touch to below freezing over and over again cant be good for longevity's sake.