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Blew 2 alternators in two weeks charge light came on less then 12 hours after install

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Blew 2 alternators in two weeks charge light came on less then 12 hours after install

Old 04-17-2017, 09:40 PM
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Blew 2 alternators in two weeks charge light came on less then 12 hours after install

Okay, need help with this "Gem" from a dark place in Arizona... I finally got the truck running well, but now I struggle with electrical problems. Tuesday of last week driving down the road and the truck misfired, radio went blank and the charge brake light came on. Had truck tested at O'Reilly. Bad regulator on alternator was the diagnosis. This alternator was about a year old from O'Reilly. Got home pulled alternator went got "new one" from O'Reilly. Put it in the truck and put the truck back together. The next day I started the truck ran my errands went home no problem. The next day, Thursday I get in the truck put about 10 - 15 miles on it when radio goes dead, (I think ) dash lights come on nothing on the truck works but head lights, four ways and the engine runs, no starter. It blew my 80 amp Fusible link. Trying to figure it out I blew another fusible link when I figure out the short has to be on a big, at least 6 gauge wire, when popping 80 amp fuse. I put an ohm meter on breaker side of fusible link to ground and I have continuity. I pull the alternator cable and have an open circuit. I reconnect alt cable and I now have 9 ohms... Obviously the alternator is bad. I pull the alternator take to O'Reilly and it confuses their computerized alternator tester. The have to reset the tester to test the alternator they give me.

So now I have installed the alternator and put the truck together. I take the truck out for a test drive and it seems fine. Later I need to run to the store and everything seemed fine. I came out of the store and start the truck and MY CHARGE LIGHT IS ON!!! I drive the truck home and as I pull into the carport the charge light goes out and everything acts fine just as I turn the engine off. Frankly at this point I do not know what I have, I am afraid to look. I had to go somewhere this morning so I pull the alternator cable out of the alternator and park it over night with my 10 amp battery charger on it because I have to be somewhere in the morning. Truck runs fine with the charge light slightly glowing, but I have not done anything else. If I walk back into O'Reilly with another bad alternator they are going to charge for the next one I fear.

Any ideas, tips hints as to what I look at/do next?

Thanks for your time,

grey
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Old 04-17-2017, 11:40 PM
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Red face

That sometimes happens with rebuilt alternators in fact quite often .

You might look for a used Denso then have it gone over by a local automotive electrical shop unless you can do the work yourself

This is of course if the problems are in the alternator and not on the harness side of the charging system.
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Old 04-18-2017, 06:06 AM
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You can go to Densos web site and look up the part number and go to ebay and buy a rebuilt denso, also on Amazon. I think you will have better luck with a Denso.
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Old 04-18-2017, 06:31 AM
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Originally Posted by greyheadedguy View Post
... It blew my 80 amp Fusible link. Trying to figure it out I blew another fusible link when I figure out the short has to be on a big, at least 6 gauge wire, when popping 80 amp fuse. I put an ohm meter on breaker side of fusible link to ground and I have continuity. I pull the alternator cable and have an open circuit. I reconnect alt cable and I now have 9 ohms... Obviously the alternator is bad.,,,
Continuity to ground, disconnect alt cable then it's open to ground, reconnect alt cable and now 9 ohms to ground.

That sounds like a problem in the cable (or any connection point that got flexed when moving the cable). Not the alternator. Alternators CAN fail to a short to ground, but they are less likely to do that intermittently than would an old piece of flexible cable.

If you put 80amps to ground somewhere, it might have left a mark (and a big spark, but you didn't get the chance to see that). Inspect the cable, and all connections in that line, carefully.
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Old 04-18-2017, 07:47 AM
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Most Toyota components are bullet-proof; the problem is in the way they are installed or connected to each other, short-cuts, poor wiring, wear on insulation, etc. Therefore, do the simple and inexpensive things first (that only need our senses - feel, see and smell cable and insulation), like like Scope says above.
Then get OEM alternator from Auto Parts Deal or other reputable places. Those OEM parts have warranty by Toyota. If you still have the original stock Toyota alt, ps save it for core return/refund

Last edited by RAD4Runner; 04-18-2017 at 07:48 AM.
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Old 04-18-2017, 10:56 AM
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Originally Posted by scope103 View Post
Continuity to ground, disconnect alt cable then it's open to ground, reconnect alt cable and now 9 ohms to ground.

That sounds like a problem in the cable (or any connection point that got flexed when moving the cable). Not the alternator. Alternators CAN fail to a short to ground, but they are less likely to do that intermittently than would an old piece of flexible cable.

If you put 80amps to ground somewhere, it might have left a mark (and a big spark, but you didn't get the chance to see that). Inspect the cable, and all connections in that line, carefully.
So if I take and run my ohm meter on the alternator cable back to the positive connector I should have continuity. Then I can adjust the meter to read the resistance. The flexing of the alternator cable will naturally give me some variation in the ohms I will read in the cable. How much variance is going to be too much? I will post what I find... But just for the record 9 ohms is not very much and I figured the increase in resistance due to the connection not being tightened down tight, but a loose connection.

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Old 04-18-2017, 10:58 AM
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Originally Posted by RAD4Runner View Post
Most Toyota components are bullet-proof; the problem is in the way they are installed or connected to each other, short-cuts, poor wiring, wear on insulation, etc. Therefore, do the simple and inexpensive things first (that only need our senses - feel, see and smell cable and insulation), like like Scope says above.
Then get OEM alternator from Auto Parts Deal or other reputable places. Those OEM parts have warranty by Toyota. If you still have the original stock Toyota alt, ps save it for core return/refund
How will I know if I have Denso core? The truck is 30 years old and the engine in the truck is 32 years old. I do have one of the alternators that was in the truck when I got it, but who knows if it was original?

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Old 04-18-2017, 11:11 AM
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This is the truck that I had two 8mm x 10mm flanged bolts left over from a tranny swap. Are there any cable hangers I might have missed putting it back together that could have allowed a cable to hang and rub and short and burn out my alternator? Just a thought, here is a link to that thread:
https://www.yotatech.com/forums/f116...lts-go-299573/

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Last edited by greyheadedguy; 04-18-2017 at 11:12 AM.
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Old 04-18-2017, 11:20 AM
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9 ohms is actually a fairly high resistance in automotive terms, and will only draw about 1.3 amps at 12 volts. Certainly not enough to blow an 80 amp fusible link. I agree that you likely have an intermittent cable short to ground somewhere. The 9 ohms could be a perfectly valid resistance value for the alternator, depending on how it's wired and constructed.
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Old 04-18-2017, 01:28 PM
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One thought I had was that possibly the key was not in the right position. That is why when I bumped the key the charge light went off and everything acted normal. I'm so paranoid at this point I did not want to deal with it at 9:30 at night and had to be somewhere in the morning. Can the ignition switch be in the wrong position and cause the lights to do this? BTW I did not have turn signals when I had the problem that night and had turn signals the next day when I drove the truck with the alternator unplugged...

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Old 04-18-2017, 09:55 PM
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I owe you all an apology, I got in my truck and turned on the ignition until all the dash lights and gauges worked. Then I backed the ignition up (I turned the key backwards) until my gauges dropped and my lights went out except my charge light. My radio worked, but I did not have any turn signals... I have just duplicated what my truck did at the store the other night, but I was too tired and frustrated to think right at the time to think about my ignition being old and not being in the right position.

So my question at this point is do I need to think about replacing my ignition switch?

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Old 04-18-2017, 10:02 PM
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Howdy Grey,
I hope you're ding Ok with the troubleshooting.
...I am afraid to look...
Don't be. Better to find out what's wrong while in the comfort and convenience of you home when you can ask us for help than when you're on the side of the road.
There's big possibility that the root cause of you problem is simple short to ground and the only way to find that is to look, feel, smell as I mentioned above.

Originally Posted by greyheadedguy View Post
... It blew my 80 amp Fusible link. Trying to figure it out I blew another fusible link when I figure out the short has to be on a big, at least 6 gauge wire, when popping 80 amp fuse. I put an ohm meter on breaker side of fusible link to ground and I have continuity....
However, A picture paints a thousand words.; It would help if you had pictures or at least a diagram so we can better understand what and where you are probing.

Where's the breaker side of fusible link?
Which fusible link are you testing? The wire or the 80-amp module that is in the fuse block?

If you're blowing your fusible link, Then we know that you have a short to ground, most likely on a thick wire, like the "B" batt to alt-wire.

I pull the alternator cable and have an open circuit. I reconnect alt cable and I now have 9 ohms...
How do you "pull the alternator cable?

When you measured the 9 ohms where was your black probe? The red probe? If you have 9-ohms to ground that should NOT blow either of the 80-Amp fusible link. Most often, only a dead short of a thick wire could blow the 80-amp fusible link. So please LOOK and find where a thick wire is making contact with ground/metal body.
What position was your ignition key in?
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Old 04-18-2017, 11:21 PM
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Originally Posted by RJR View Post
The 9 ohms could be a perfectly valid resistance value for the alternator, depending on how it's wired and constructed.
Actually, IF the "B" wire were disconnected from the alternator screw-post. Resistance between alternator screw post and ground should be multiples of a mega-ohm.

Originally Posted by greyheadedguy View Post
So my question at this point is do I need to think about replacing my ignition switch?
Hi Grey,
If I may reiterate, please do NOT suspect your ignition switch until you have seen, felt, smelled the condition of your thick cables and insulation. Nothing technical about this task. Just need to dive in there.

OK, now you'd have to use your multimeter for this. Please verify the following:
Disconnect your negative battery cables.
Disconnect everything connected to alternator screw-post/terminal shown below.
Multi-meter in Ohm range, negative probe to body ground, positive probe to that screw-post/terminal. What do you read?

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Old 04-19-2017, 03:18 PM
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Originally Posted by RAD4Runner View Post
Actually, IF the "B" wire were disconnected from the alternator screw-post. Resistance between alternator screw post and ground should be multiples of a mega-ohm.


Hi Grey,
If I may reiterate, please do NOT suspect your ignition switch until you have seen, felt, smelled the condition of your thick cables and insulation. Nothing technical about this task. Just need to dive in there.

OK, now you'd have to use your multimeter for this. Please verify the following:
Disconnect your negative battery cables.
Disconnect everything connected to alternator screw-post/terminal shown below.
Multi-meter in Ohm range, negative probe to body ground, positive probe to that screw-post/terminal. What do you read?

I'll go and check this, I just finished another project I was working on and was able to find my multi-meter again.

1.) I do want to make the comment so it is clear that the continuity and the 9 ohms from the heavy alternator cable to the body were read with the "bad alternator."
2.) As far as black lead or red lead to the frame or alternator doesn't seem to matter from what I understand, but I will do it your way.
3.) When the 80 amp fusible link blew other then getting burned from the sparks from the ground cable and the negative post, I did not smell any hot or melting insulation. I'll post a picture of my alternator cable when I get there.
4.) I have only one cable bolted to my alternator and have had only one cable on my Toyota trucks. Am I missing something here?
5.) My alternator cable is max 2" - 4" before it goes into the wrapping of the harness...

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Old 04-19-2017, 04:10 PM
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Hi Grey,
Oh yeah, polarity USUALLY does not matter when measuring resistance but could tell us something when rectifiers such as in the alternator are involved
Originally Posted by greyheadedguy View Post
the continuity and the 9 ohms from the heavy alternator cable to the body were read with the "bad alternator."
Was the cable (A) disconnected from the fuse block and still connected to the screw-post/terminal on alternator, OR
(B) The cable disconnected from the alt screw-terminal and still connected to the fuse block?
If A, and there is only 9- ohm between the alt "B" wire and ground, then there is a problem with the alternator.
If B, and there is 9-ohm from battery cable and ground, like mentioned above, that is normal load an will not blow the 80-Amp fusible link.

I have only one cable bolted to my alternator and have had only one cable on my Toyota trucks. Am I missing something here?
There should only be one cable screwed on to the alternator terminal. The other end goes somewhere on the fuse block.
Good point. Why don't you trace all the cables connected to the battery to make sure they go to right place, have insulation and do not rub against body metal?
From positive terminal:
1) Fusible Link wire to fuse block.
2) THICK cable to one side of the starter solenoid.

From negative terminal:
1) One wire to body ground inside fender.
2) One thick cable that goes to the engine block. This is also the ground cable for the starter.





When the 80 amp fusible link blew other then getting burned from the sparks from the ground cable and the negative post, I did not smell any hot or melting insulation.
Why did the ground cable spark? Was it not tightly connected to body ground? What did it touch that made it spark?
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Old 04-19-2017, 04:25 PM
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Okay, ran it, cable looks fine, no smells and no reading on the ohm meter or meter showed an open circuit.

I have looked at the pictures and it looks as if the cable could short on the alternator so moved what is left of that boot/insulator over the bare copper.
Anyone know where I can find a one of those?

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Attached Thumbnails Blew 2 alternators in two weeks charge light came on less then 12 hours after install-p1110257.jpg   Blew 2 alternators in two weeks charge light came on less then 12 hours after install-p1110265.jpg  
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Old 04-19-2017, 08:12 PM
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Originally Posted by greyheadedguy View Post
...that boot/insulator over the bare copper.
Anyone know where I can find a one of those?
Terminal cover, terminal boot...
https://www.amazon.com/gp/aw/d/B000CSZIYI/ref=mp_s_a_1_1?ie=UTF8&qid=1492660901&sr=8-1&pi=AC_SX236_SY340_QL65&keywords=alternator+termi nal+boot&dpPl=1&dpID=413MOzeUC%2BL&ref=plSrch

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Old 04-19-2017, 08:52 PM
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I think you've got it there on that alternator cable. That cable is tied straight to your main battery supply. If it is touching the alternator housing then you would have enough amps running through your chassis to blow your big fuse when you connected your negative cable. That will also kill an alternator.

On your ignition, you've probably already figured out what's going on. Your key or ignition lock is worn out, allowing you to pull the key out without depressing the button that would, under normal circumstances, allow you to remove your key. When I first got my 1st gen 4Runner that didn't have a radio installed, I would remove my key and go in the house for the night and in the morning, the battery would be weak or dead. Finally figured out that the electrical system was still active since I hadn't pressed the key lock button and fully turned the key to the off position. I would have known something was up if it had a radio which would have stayed on after I shut it down.
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Old 04-19-2017, 09:24 PM
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Originally Posted by RAD4Runner View Post
Hi Grey,
Oh yeah, polarity USUALLY does not matter when measuring resistance but could tell us something when rectifiers such as in the alternator are involved
Rectifiers is getting over my head...

Originally Posted by RAD4Runner View Post
Was the cable (A) disconnected from the fuse block and still connected to the screw-post/terminal on alternator, OR
(B) The cable disconnected from the alt screw-terminal and still connected to the fuse block?
If A, and there is only 9- ohm between the alt "B" wire and ground, then there is a problem with the alternator.
If B, and there is 9-ohm from battery cable and ground, like mentioned above, that is normal load an will not blow the 80-Amp fusible link.
1.) The fusible link was out of the block with the negative post disconnected from the battery.
2.) The fusible link was blown so there was no connection to the positing battery post. So I was testing the backside, the side that goes to the fuse block.
3.) I was testing (I guess) 'B' cable that bolts to the alternator. With cable connect4ed to bolt with nut tight on it I had continuity with the frame of the truck. First test.
4.) Disconnected 'B' cable ( I think it is) Open circuit between 'B' cable and screw on fuse block side of fusible link (still blown condition with fusible link.)
5.) Reconnected 'B' cable to bolt on alternator, just a few twists on the bolt, loose connection, Ohm meter read 9 ohms between 'B' cable and screw on fuse block side of fusible link (still blown condition with fusible link.)
6.) Disconnected bolted cable on alternator and again had an open circuit between 'B' cable and screw on fuse block side of fusible link (still blown condition with fusible link.)


Originally Posted by RAD4Runner View Post
There should only be one cable screwed on to the alternator terminal. The other end goes somewhere on the fuse block.
Good point. Why don't you trace all the cables connected to the battery to make sure they go to right place, have insulation and do not rub against body metal?
From positive terminal:
1) Fusible Link wire to fuse block.
2) THICK cable to one side of the starter solenoid.

From negative terminal:
1) One wire to body ground inside fender.
2) One thick cable that goes to the engine block. This is also the ground cable for the starter.
From positive terminal:
1.) I had an extra 10 gauge wire attached to the positive post on the battery that went into the fender then into the cab of the truck, but it had a wire nut on iy. I have removed this wire it no longer exists.
2.) Starter cable
3.) My fusible link wire was cut in half and spliced to a 10 gauge wire that went to the battery post. I have replaced this with the fusible link wire that was in my 85 two wheel drive truck. They looked the same except the one from the 85 was not spliced and was the right length.

From negative terminal:
1.) I have a thick cable that goes to the fender of the truck.
2.) I do not have a cable that goes from my negative battery post to my engine. Neither truck (my 85 2x or my 87 4x4) was set up this way.
3.) I do have a ground cable that goes from the body of the truck to the engine, but can't remember where it is at the moment, but I remember hooking it up when I put this engine in the truck.

Originally Posted by RAD4Runner View Post
Why did the ground cable spark? Was it not tightly connected to body ground? What did it touch that made it spark?
I can only guess it was because of the dead short in the alternator when I tried to put on the negative post on the battery...

I think I answered everything, Thank you for your time,

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Old 04-19-2017, 09:36 PM
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Originally Posted by Charchee View Post
I think you've got it there on that alternator cable. That cable is tied straight to your main battery supply. If it is touching the alternator housing then you would have enough amps running through your chassis to blow your big fuse when you connected your negative cable. That will also kill an alternator.

On your ignition, you've probably already figured out what's going on. Your key or ignition lock is worn out, allowing you to pull the key out without depressing the button that would, under normal circumstances, allow you to remove your key. When I first got my 1st gen 4Runner that didn't have a radio installed, I would remove my key and go in the house for the night and in the morning, the battery would be weak or dead. Finally figured out that the electrical system was still active since I hadn't pressed the key lock button and fully turned the key to the off position. I would have known something was up if it had a radio which would have stayed on after I shut it down.
I had that problem on my 85 Toyota 2x truck where the key could fall out of the ignition. I fixed it by getting a key made from the key code on the passenger's door lock. Take that code down to Toyota and they can make you a New Key from the code. My key cost me $10 but was well worth it. I bought one key from them and then went to the place I trust most to make keys and had them make 3 keys for me. The new key from code resides in my safe so it does not get used. The new keys will not pull out of the ignition without pushing the button. Best thing you can do is take the lock in and let them read the key code and they have a lock to test the new key in.

What I need to figure out is can I replace the ignition switch (the electrical switch) that runs to the plug and fix my problem with my tired, worn ignition switch? The one on my old 85 is in better shape then this one in my 87 that I am driving...

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