Jump to content
hamkid

Alternator is failing questions and concerns

Recommended Posts

Yes the one from up front and the converter wire. Because of the isolator it will have no effect from current going the other direction it stops right at the isolator once the engine is running the current flow can pass to your coach battery, now because you have the older style converter it actually disconnects from the coach battery when you are not plugged in. I know this all is a bit hard to grasp but the bottom line it separates the two batteries when the engine is not running using solid state diodes. To be honest I prefer the simpler relay system but in your case it would require some rewiring and you probably have a functioning isolator.

Share this post


Link to post
Share on other sites

So I tested to isolator today. There was current flowing sometimes and sometimes not. After testing the isolator I tested the alternator again. It was not charging the battery. If the alternator is connected to a non working isolator will it affect the performance of the alternator? 

Share this post


Link to post
Share on other sites
On 1/8/2020 at 8:01 PM, hamkid said:

So I tested to isolator today. There was current flowing sometimes and sometimes not. After testing the isolator I tested the alternator again. It was not charging the battery. If the alternator is connected to a non working isolator will it affect the performance of the alternator? 

 Start it again and see if you get something close to the same reading on the two isolator posts that is the direction the current must flow. If so you have an alt issue. 

Share this post


Link to post
Share on other sites
Just now, Maineah said:

 Start it again and see if you get something close to the same reading on the two isolator posts that is the direction the current must flow. If so you have an alt issue. 

Be a good ideal also to check the drive belt tension

Share this post


Link to post
Share on other sites

Removed the alternator and had it tested. It passed. When reinstalled noticed the belt was chewed up in a spot. Will remove fan and main belt to replace alternator belt. Hopefully that will resolve the issue.

Share this post


Link to post
Share on other sites
17 hours ago, hamkid said:

Removed the alternator and had it tested. It passed. When reinstalled noticed the belt was chewed up in a spot. Will remove fan and main belt to replace alternator belt. Hopefully that will resolve the issue.

That may well be your answer the alternator on those needs to be damn near bow string tight they are over driven to make them charge at lower rpm's

Share this post


Link to post
Share on other sites

Pictures of the old fan/alternator belt. Replaced today. Will test and give update tomorrow.

001.JPG

002.JPG

Share this post


Link to post
Share on other sites

Yep that's junk like I said they really have to  be tight.

Share this post


Link to post
Share on other sites
On 12/27/2019 at 7:53 AM, Maineah said:

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.

I was under the belief that even the internal regulated alternators needed the exciter circuit of the isolator to be hot with ignition on. The alternator output wants to see 12v + to energize? I ask because my 90 had the 4 wire isolator. Not sure about the regulator. While cruising down the freeway the isolator shorted internally to ground. Took out my alternator and left it smoking. Luckily I was able to pull over next to an auto parts store, buy a new one, bolt it up and drive off. That little delay allowed us to see a spectacular sunset on the way to the coast! 

Share this post


Link to post
Share on other sites
16 hours ago, Gulfstream Greg said:

I was under the belief that even the internal regulated alternators needed the exciter circuit of the isolator to be hot with ignition on. The alternator output wants to see 12v + to energize? I ask because my 90 had the 4 wire isolator. Not sure about the regulator. While cruising down the freeway the isolator shorted internally to ground. Took out my alternator and left it smoking. Luckily I was able to pull over next to an auto parts store, buy a new one, bolt it up and drive off. That little delay allowed us to see a spectacular sunset on the way to the coast! 

Nope the newer ones are self exciting. I kind of remember round plugs vers square. I would say probably some were wire for 4 wire when it really was not needed. The alt light on the newer ones supplied the exciter voltage.

Share this post


Link to post
Share on other sites

Well I replaced the belt and it is still not charging the battery. I had the alternator tested and it checked out with the parts store. Is there anyway it could be bad or intermittent even if it passed a bench test? Should I buy a new one just to see?

Share this post


Link to post
Share on other sites

I have had bad altinators pass the test at orileys.  And in fact it was on my toyota dolphin. But my scenario was a little different.  Mine was over charging 17 to 20 volts. That too will cause your battery light to come on. I pulled it out bench tested it at orileys guy tells me its fine, I said I don't believe your machine. I'll take a new one. They are pretty cheap. Fixed my problems. And it came with a lifetime warranty. 

Edited by 86Dolphino

Share this post


Link to post
Share on other sites
16 hours ago, hamkid said:

Well I replaced the belt and it is still not charging the battery. I had the alternator tested and it checked out with the parts store. Is there anyway it could be bad or intermittent even if it passed a bench test? Should I buy a new one just to see?

OK here is the deal when the isolator was installed the original alt wire to the battery was cut and spliced to join the terminal on the isolator two things, a bad connection at the splice or a toes up isolator. At this point I gather you have a voltmeter to test voltage, test the voltage at the "A" post on the isolator (engine running) then at the 1 and 2 posts. If you get nothing join the A to one of the 1 or 2 posts and see what you get. If it show a charging voltage replace the isolator if not then you need to find out why there is no voltage at the A post, first place to look at is the splice.  

Share this post


Link to post
Share on other sites

https://1drv.ms/u/s!ArCFZ6MnxmgejWZx_g41vWkGHO7V?e=BbhYvc

I don't know what's going on with this website, it let me post my pics the other day and now it won't. Please visit the link to view pics. I bought a new isolator just to be sure. Connected wire from battery to post 1. Voltage tested good. Did not connect alternator to post. Did not connect cabin battery to post. Still need to test which wire is alternator and which is from cabin. Did not take note last time. If you notice the new isolator is slightly bigger than the old one and will not line up with the old screw holes. Will this cause any issues since parts of the isolator are not touching the body?

Share this post


Link to post
Share on other sites

There is a size limit to the photos. When taking photos for this site I reduce the size first 

Share this post


Link to post
Share on other sites

That's a nice looking insulator.  Makes mine look inadequate. Lol. But I dont have problems yet so I'm leaving it. 

Share this post


Link to post
Share on other sites

For my Samsung open camera hit the cog and it's the first option 

Screenshot_20200118-111305_Camera.jpg

Screenshot_20200118-111246_Camera.jpg

Share this post


Link to post
Share on other sites
3 hours ago, hamkid said:

https://1drv.ms/u/s!ArCFZ6MnxmgejWZx_g41vWkGHO7V?e=BbhYvc

I don't know what's going on with this website, it let me post my pics the other day and now it won't. Please visit the link to view pics. I bought a new isolator just to be sure. Connected wire from battery to post 1. Voltage tested good. Did not connect alternator to post. Did not connect cabin battery to post. Still need to test which wire is alternator and which is from cabin. Did not take note last time. If you notice the new isolator is slightly bigger than the old one and will not line up with the old screw holes. Will this cause any issues since parts of the isolator are not touching the body?

OK the 1 and 2 posts provided the batteries are connected should have battery voltage you can tell what is what by connecting them one at a time. The A post engine not running should not. Once the engine is running the A post should have voltage. Short explanation, think of the 1 and 2 as a one way valve they only allow current to flow one way they are always power but the one way valve does not let power to flow to the A terminal it can only let power flow from it. Both of the one way valves are connected to the A post. Both are joined to the A post but because the power can only flow from the A post the two batteries can not flow power to one another. So stationary the A post will have no voltage. 

Share this post


Link to post
Share on other sites

Thank for the diagram. The triangle and the bar tell the story the point is the direction the current flows the bar is the current block so this is how two batteries can be joined without discharging one another and both be charged at the same time. There is a great deal of perceived mystery inside of that little box but once you see how it actually works it really is a simple device it's just two high current diodes nothing more because diodes are less than 100% efficient there is loss to heating that's why it has cooling fins. 

Edited by Maineah

Share this post


Link to post
Share on other sites
On 1/18/2020 at 10:35 AM, hamkid said:

How do you reduce the size of the pics?

Download Gimp https://www.gimp.org/ . It can resize images to what ever size you need. The system is set to 800x800 pixels max or less.

Share this post


Link to post
Share on other sites

Installed new alternator and connected isolator. Still not charging. Now the dash battery light comes on, did not do that before.

Edited by hamkid

Share this post


Link to post
Share on other sites

OK again the original alt wire from the alt B+ (big wire) to the battery was cut and rerouted when the isolator was installed this is important because it is the only path back to the batteries. If it is a poor job or damaged that could explain your issue. See if you can find the splice take the tape off inspect the joint if it's corroded or shows signs of heating (kind of brown) it needs to be redone. It's hard to see from my house but I believe it's a #8  factory wire white with a red stripe beyond that on the trip to the isolator it's anyone's ones guess on color.

Share this post


Link to post
Share on other sites

I attempted to do voltage test on the new alternator with neg. lead on neg. post and pos. lead on alternator post. Should I see the same voltage as the battery 🔋  or 13 to 14 volts ️ coming out of the alternator? Or did I perform the wrong test? The output was very low.

Share this post


Link to post
Share on other sites

With your voltmeter hook the - lead to the engine block and + ton the alternator post. You should have 13.5v+.

If this test is good you may have a bad engine to chassis ground or even a bad ground lead on the battery

Share this post


Link to post
Share on other sites

With the engine off you probably will see no voltage at the alt output. Or the A terminal at the isolator. Once it's running you should see voltage at the isolator A terminal and rising voltage at 1 and 2. I kind of hate to see what this wiring looks like. If you can fabricate a jumper wire from the alt output wire (the big one) to the truck battery + see what that gives you at the truck battery. 

Share this post


Link to post
Share on other sites

Returned alternator. Purchased another from different store. Connected - neg. lead to engine block and + pos. lead to alternator terminal. Tested less than a volt. Wires do not appear damaged. Did not make a jumper wire from battery to alternator. 

Share this post


Link to post
Share on other sites
13 hours ago, hamkid said:

Returned alternator. Purchased another from different store. Connected - neg. lead to engine block and + pos. lead to alternator terminal. Tested less than a volt. Wires do not appear damaged. Did not make a jumper wire from battery to alternator. 

Do that, it will eliminate any wiring issues. If it works then you have an issue with the modified wiring then you have two choices repair the wiring or abandon it and run a new #8 wire from the alt to the A terminal on the isolator.

Share this post


Link to post
Share on other sites

I wanted to double check fuses with a test light 💡. At the engine box I’m getting nothing at the two 10 amp HEAD(LH),HEAD(RH). Nothing at 7.5 amp CHARGE. 10 amp HAZ-HORN tested good. Check under fuses box and wires appeared ok. Did not check under tape. What should I do next?

Share this post


Link to post
Share on other sites

The lights have to be on to check the fuses. The only wire that was disturbed was from the alt to the battery it could have been done in more than one way. Somewhere there is a splice that is not factory. Somewhere there is a #8  (thick wire)  from the alt I'm reasonably certain it's white with a red stripe it will be joined to most likely a wire of a different color. The only thing the splice would effect is the charging system not the lights etc. 

Share this post


Link to post
Share on other sites

Found it! For some reason I decided to move the battery cable and alternator wire to the same post on the isolator. When I did that it started to charge the battery a little more than before. Then I tracked down the splice. After I fully removed the tape from the splice it starting  charging 14 volts at the battery. What’s next?

CB6CB169-CF2F-44B7-A8A8-79E05F3224A4.jpeg

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...