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hamkid

Alternator is failing questions and concerns

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My alternator has failed in my 1985 Toyota Escpaer, but was replaced two years ago. I first noticed for some time that the head and dash lights would flicker when the vehicle was in idle, then I totally lost power when driving. Should I assume that the alternator failed or are there other things I should test? The battery is tested and good. Where is the alternator fuse or relay to check? I was reading this post and will test the isolator along with the alternator.

Any other suggestions or comments would be helpful. Just wondering if there is anything in the system that would make an alternator fail. Does the amount of drive time or distance have anything to do with the lifetime of an alternator? Will post pics later.

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It is internally regulated so it would be hard to say why it failed. Could be the regulator could be a diode failure or even an issue with the brush pack. I'll assume who ever checked it did so at the battery so this could throw a monkey wrench into the picture if you have a solid state isolator. The voltage output from the alt has to pass through the isolator if the diode is bad this can't happen so if checked at the battery it would show no output. That is fairly rare but possible. If it has a mechanical relay that would not be an issue.

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I tried to upload the pictures of the isolator. Website kept giving error "-200", any idea what that is about? The pictures can be view at the link below. Also how tight should the belt on the alternator be? There is some slack to it. Should I tighten it before I attempt any voltage testing?

 

https://1drv.ms/u/s!ArCFZ6MnxmgejF7jaHjig4G_tMFM?e=GClk71

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Have you checked the belt is tight enough and in decent condition? A slipping belt would give the symptoms you noted. Otherwise as stated likely a diode in the regulator, one of the windings or the brushes are failing.

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1 hour ago, hamkid said:

I tried to upload the pictures of the isolator. Website kept giving error "-200", any idea what that is about?

I think this is caused by image files that are too big. Your original for this one was 46MB. This version is ~3.8MB.

image.png.da79604d5f7c8f2054dfb7311bb1c40c.png

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The belt did need some more tension. Before tightening battery reading did not change, after tightening battery read 14 volts, seems to be working. Will test will load and update status. Derek how did you decrease image size, Photoshop?

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Sounds like that was the issue. Most alternators will put out about 14.4v but I haven't checked my camper.

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OK your isolator  is doing absolutely nothing other than a contact point. It is not acting as an isolator the way it is wired it is using both batteries at the same time no matter what, good way to end up with a dead truck battery. Next question is the isolator bad? My guess it is not just wired wrong someone was trying to solve a problem that probably did not exist. Trying to fix it at this point probably won't happen because the terminals are just too rusty. Because the alt. wiring was modified to use a solid state isolator it would be the best bet to replace it with the same. The belts on a Toyota camper need to be close to bow string tight they are overdriven meaning they were geared to turn max RPM for max output (big drive pulley small alt pulley). A new isolator should come with a diagram of how it is to be wired.

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I do not currently have a battery in the house, only in the engine. Should I fix the isolator immediately or when install a second battery?

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I still would check the wiring to the coach if it is disconnected it has to be well taped up so that it can not short to the the truck frame work that is an unfused circuit and the way it is now wired it is hot all the time the engine is running. As it is it still should charge the truck battery so you should be good to go until you deal with the issue and install a coach battery. The isolator really is not a magic box it consists of two high current diodes being less than 100% efficient is why it looks complex the cooling fins dissipate the heat from from the diode efficiency loss. That is one reason I prefer relay type isolators. Generally solid state isolators are branded "A" and 1 and 2 the 1 and 2 are the battery leads they are interchangeable the A is from the alternator. When it was originally wired the alternator wire was cut and moved to the A post that is why it would be easier to replace the isolator with the solidstate one.

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Any guess as to why someone would attempt to set it up this way? If the isolator tests good should I keep it?

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15 hours ago, hamkid said:

Any guess as to why someone would attempt to set it up this way? If the isolator tests good should I keep it?

It over the years it has need labeled as a "mysterious box" so it gets blamed for all kinds of electrical issues from tail lights to poor radio reception they have one purpose and that is purely for isolating/charging batteries and have no effect on any thing else.  They do fail but it's not chronic. I would be inclined to buy a new one only because it is so rusty and if you break the stud off holding the wires down there you sit until the new one arrives. For your needs they run 30-40 bucks you don't need the unit that does everything except wash the dishes. When you get ready just jump in with questions and we can walk you through the check list.

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That is for the older alternators with an external regulator the newer ones are much simpler only 3 pins. There was some odd balls with an exciter wire for a couple of years but they were fairly early ones. It would be wired the same except there would be no "E" (exciter) wire.The 1 and 2 wire are interchangeable (makes no difference) and the A goes to the alternator. Because the alt wire has already been cut that should not present a problem just a matter of connecting it to the A terminal. Either there was problem or lack of knowledge and that is why all the wires are joined together this of course defeated the concept of an isolator and would be a good way to end up with 2 dead batteries.

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Two of the wires will have battery voltage (of course the batteries need to be hooked up engine not running) Remove all 3 from the post and test one at a time The one that has no voltage is the "A" wire the other two are battery wires it does not matter 1 or 2 all though it's customary for the truck to be 1.

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Installed a house battery and tested wires. Got a reading on one, and a negative reading on the other. What should I do about a negative voltage reading?

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37 minutes ago, hamkid said:

Installed a house battery and tested wires. Got a reading on one, and a negative reading on the other. What should I do about a negative voltage reading?

What does your meter reading say what is the voltage and what battery is under test? It is easy to reverse you coach battery leads and will not cause ill effects until it is under load or the converter is working (plugged in). Reversing your meter leads will do the same thing The red meter lead is +. The truck battery reversed will give you arcs and sparks pretty much right away. So take the black meter lead and connect to a good ground touch both of the battery wires they should be something close to 12 volts the A wire should be close to zero.

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When I tested the wires my voltmeter negative lead was clipped to the negative terminal on the engine battery, would that be an issue? I can’t retest until tomorrow.

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No that's ok but both leads have to be done that way it is very possible your coach battery posts are reversed if you are showing 12 volts negative. A little hint the negative post on a battery is smaller than the positive one. What ever one is testing correctly you can go a head and connect it to the isolator 1 or 2 post.

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The battery I used to test the coach belongs to my Toyota Corolla. I swapped it out for the test. 

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That's ok they all work pretty much the same. Make sure the cables are on the proper posts +/-.

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Many had extra smaller wires some were + some were - one of them went to the coach wiring the other to the isolator and some had a ground wire. Generally the + was red. What you can do is disconnect the smaller wires then hook up the wire at the isolator to the battery terminal go to the coach battery and find the "hot" wire with one meter lead on ground that will give you a start. One of the other wires will be the coach power wire if there is one left over it most likely is a ground wire.

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How about a picture of the coach battery area?

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Well that's a bit of help it looks like there is a circuit breaker I can only see one post so I'm not sure what's on the other side. The green wire is most likely a ground. The black may go to the isolator that I believe is the key making all of the #8 black wires hot from the isolator and the coach battery. and it looks like it's landed under the 30 amp fuse in the fuse box. Mine you this is speculation. The red wire on the fuse panel probable goes to the converter. 

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Will plugging into shore power help me determine anything about the wires?

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Possibly. It should put out 12 volts+  The original posted picture is correct disregard the wiring for "E" your's does not use it. The one for aux loads also connects to the converter.

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I think I am confused about how the wiring works. The wire coming from the converter is positive? The wire that goes to the isolator is negative? 

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On 1/5/2020 at 7:27 PM, hamkid said:

I think I am confused about how the wiring works. The wire coming from the converter is positive? The wire that goes to the isolator is negative? 

No it is + With the converter on it should be in the 12 volt range positive. That wire should be landed on the coach + battery post along with the isolator wire. The diode in the isolator can be thought as a one way gate it only allows  current to flow one direction. Diodes - learn.sparkfun.com this is the device that stops current flow to both batteries at the same time when the engine is not running it only allows power to flow one direction.

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