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Location To Check Alternator Output


ToyoGuy
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For all the Spark-meisters out there...

Is it legitimate to check alternator output at the middle (+) lug of the battery isolator (wired to the alternator, near firewall), with the Neg VOM probe on a good ground?

This is with the other two wires connected to the isolator. (Coach and Chassis)

Why, you ask?

Why get greasy down there, pulling connections off the back of the alternator, if I don't have to?.....  ;)

Hope yer all well.

BR,

TG

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i usually check on the battery itself. although i was recently bit doing it this way. i was not seeing the 13-14 volts on the battery when running so i assumed it was the alternator. Turned out to be a wiring issue in between. But i believe if you see the correct output at the battery your in good shape.

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yep, the isolator connection is electrically the same as the battery +. if you're looking for alt amps, the lead off the alt. is the only way

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1 hour ago, ToyoGuy said:

For all the Spark-meisters out there...

Is it legitimate to check alternator output at the middle (+) lug of the battery isolator (wired to the alternator, near firewall), with the Neg VOM probe on a good ground?

This is with the other two wires connected to the isolator. (Coach and Chassis)

Why, you ask?

Why get greasy down there, pulling connections off the back of the alternator, if I don't have to?.....  ;)

Hope yer all well.

BR,

TG

The answer to your question is yes!

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Thank to all for your response, and I agree mpanzar, the less wire between, the better !

 

BR,

TG

 

P.S. Is it true that the colored plastic covering on all those wires holds the smoke in?

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Good plan, one caveat you are assuming the wire is good. From your question it sounds like you have a solid state isolator (metal box with fins)

Check center post to ground, post 1 to ground (truck battery) post 3 to ground (house battery).  There may be a voltage loss (.7v) between center post and the others due to diode restance.

Check v at both batteries. The voltage should be the same as the voltage on the 1 & 3 posts. IF the voltage is lower on the battery than the post, then you have a WIRE problem.

When I first got my Escaper I did these checks and found that the wire from the isolator to the house battery was 7 different wires twisted and taped together.

I made a single wire run of 10 gauge wire and gained 1.4v at the battery

The old style solenoid isolators have less v drop, but a limited life span.  

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Heads up on testing these beasts...  (disclaimer most of us know all this, this is for newbies on here or guest readers)  First you sometimes have to blip the throttle to get it charging.  Next if your house battery is dead, or bad, it can give you some weird charging system readings.  If your alternator appears to be putting out, but not seeing it at the engine battery...  If need be disconnect the house battery temporarily to verify.    

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The Alternator is not self exciting it has to have a battery connection to make power.

 

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16 hours ago, WME said:

"Good plan, one caveat you are assuming the wire is good. From your question it sounds like you have a solid state isolator (metal box with fins)

Check center post to ground, post 1 to ground (truck battery) post 3 to ground (house battery).  There may be a voltage loss (.7v) between center post and the others due to diode restance.

Check v at both batteries. The voltage should be the same as the voltage on the 1 & 3 posts. IF the voltage is lower on the battery than the post, then you have a WIRE problem."

 

Solid state it is, and thank you very much for this insight WME.

 

On the last,

I got no idea Linda, so much magic eludes me on youtube :huh:

TG

 

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initially the alt needs to be started by power from the bat. once it is operating, removing the battery doesn't turn it off, but removing the battery while the alt is working will likely kill the alt because it sees the missing battery as a giant battery and goes to full output which can't be sustained

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1 hour ago, linda s said:

And yet this car is still running and alternator still putting out power after he removes the battery.

Can a Car or Truck Run with No Battery? How Vehicle Alternator and Electrical System Works! - YouTube

Please explain

Linda S

There are different types of alternators. GM makes a very nice 1 wire alternator that hot rodders love.

Once the alternator is running and "excited" it will keep producing power without a battery and the engine will stay running. And without a blocking diode in the wiring system you can't shut the engine off.

However there some alternators that won't produce power when an engine starts untill they are "excited" and that turns them on.

Externally excited or self excited, here ya go...https://eblogbd.com/details-of-excitation-system-of-alternator/

Warning MAY cause headache when reading 

 

Edited by WME
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OK so initially all this started because Toyoguy replaced his alternator and the new one was generating 19.5 volts. I recommended a few that were genuine Nippondenso rebuilds but he must still be having issues. How could an alternator be generating that much power. Even a completely dead battery wouldn't cause that big of a draw. Anybody got any ideas? Maybe just a really bad rebuild? 

Linda S

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sounds like it is full fielded=  battery applied to rotor instead of regulator controlling rotor voltage. an alternator can produce 110v ac. they also produce near full out put at idle

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Occam's Razor. .. A bad rebuild

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So here it is Saturday, and I have neglected to update, plus... I just had to follow-up after WME cited Occham's razor.

I love this forum 'cause I get to hang out with worldly peoples !!

 

For the uninformed: Occam's Razor refers to the process of removing all of the unneeded details and returning to the core issue of the problem. It also implies that the solution with the greatest odds of being best is the one that has the simplest logic."

 

So anyway.....

My SunRader was with my now ex-mechanic for about a week and a half for a cooling issue that was solved. When I got it back, I took it for a 1 hr drive up the coast and upon arriving, I discovered that it was way over-charging the system. ( evident in coach batteries, cab battery, distribution panel and solar controller ). After repairing all systems and fuses, and replacing batteries, I took readings and saw the 19 volts that Linda referenced above in this thread. After looking around on-line, I found this somewhat helpful link about over-charging:

https://sparkys-answers.com/2009/02/1984-toyota-pickup-charging-system-over.html

I then checked voltage for the voltage-sensing wire at the regulator (externally mounted) and had 12+V there, but all plug contacts looked mega-corroded, so I cleaned every connection/plug shown in the article. That brought me down to 15.6 volts @ low idle, and this is with all batteries charged to at least 12.9 Volts prior to test.  Still too high, according to all available info.

Because removing the alternator is a ROYAL pain in the butt in my rig, I replaced the regulator this morning.  No joy, still 15.6 VDC @ idle with fully charged batteries...

I then pulled the alternator to test at O'Riellys and sadly, it turns out, it cannot be checked outside of vehicle, by them anyway. No more specialty auto-electric shops around here anymore, must all be in Texas or Idaho.

Therefore,.... Occhams razor!

The old alternator is a NAPA brand, either Mexican or Chinese. I will be next looking for a replacement alternator that I won't have to worry about quality-of-construction on. (gotta get some laughs on that line) The Denso search starts at Rock Auto, one of Linda's faves.

I did get a replacement alternator on guarantee at NAPA, but I won't install it because of suspect quality issues, the hassles pulling it back out and previous failure costs.

I'll keep all posted.

Much thanks for all data.

BR,

TG

 

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Ok get a spray bomb of deoxit and blast the connectors plug them back in and out a few times. The system relies on a battery reading or it will go full smoke no matter what you do. I can't remember what year they stopped using external regulators but they were what controlled the charge current not the alternator. With no sensing they will charge as tight as the alternator will produce it. The voltage is applied to the F terminal if it is way above battery voltage it thinks the battery is dead.

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Thanks Maineah,

I previously used CRC Electronic cleaner and small bits of #500 paper with dental tools, but will back track,"excersize" the connections again and visually re-check everything. Sometimes these old spade-connectors can be tricky.

It's frustrating because 15.6 V is only about a volt above commonly referenced threshold for charging a 12 v batty.

Check and re-check....

TG

 

 

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Try with a different multimeter. I didn’t have my fluke one day so used a Chinese substitute. Voltage readings were unusually high. Retested with the fluke and voltage was spot on. Chinese POS went into the trash.

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Good, dime stores are not you best source  of quality equipment. 13.8 is a good charge voltage, a battery is a resistance load, A fully charged resting battery voltage is 12.8.

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  • 2 weeks later...

 

So here's the update on the (1 Volt +/-) overcharge condition, new voltage regulator, new alternator, all plugs examined and cleaned, grounds cleaned and batteries tested good or were replaced and were charged before these voltage tests were done at the isolator, which also tested good for isolation.

Scenarios were:

#1- Alt cable and truck- battery lead bolted together on middle (usually Alt)  post (eliminating isolator) the world is good. Battery charging at 14.5 V. Didn't check empty outer posts.

#2 – Alt cable on middle post and Coach-battery on number 2 side-post. No truck-battery hooked up, but the empty truck-battery post reads 14.18 V.  The world is still good @ 14.3 V on Alt post and 14.18 V @ Coach-battery post.

#3 - All cables hooked to respective correct-installation posts and getting 15.5 on Alt post and 14.5 V on both Coach-battery and truck-battery posts. If this is left this way @ idle, the voltage climbs towards 14.8 V and beyond on both coach and truck batteries. I have not left it running like this to find out how high ...

#4 – Alt post hooked up and truck-battery post both hooked up and Coach-battery post empty. Empty Coach post 14.5 V, Alt post 15.7 V, truck battery post 14.7 V.

Key out of ignition, all cables installed per normal, both truck-battery and coach-battery posts read 13V. Alt post starts @ about a 5 V reading and slowly declines to almost 0 V, but if the leads to the VOM are removed, the voltage slowly climbs again. Shouldn't there be no voltage here? Weird science.

I think I need to do all tests again, but use the hot connection at the back of the alternator and see if there's any difference. Somehow the regulator thinks the isolator needs more current. Might need to re-check the voltage sensing wire/plug interface. Ah, schematics, what fun.

BR,

TG

#1.jpg

#2..jpg

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How about scenario 1.5?

Take scenario 1 and add the house battery to it's proper post (#2).

Just for grins how about a 2.5? Alternator to A, house battery to A and truck battery to #1

 

A diode typically loses .7v across it

 

Somewhere in the dark recess of my feeble mind, I seem to recall that some Toyots need a 4 post isolator. The 4th post is the exciter voltage for the alternator.

Image3.jpg

Edited by WME
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Well... 1.5 is thought provoking. Guess I never considered it !

Could this be legit?

Lessee...house is still blocked by a diode from draining the truck battery, but alas, the truck can drain the house battys methinks.

2.5 leaves me where I was, with 15.7 V at the truck battery continually.

I'm tempted to suspect the isolator, but "sources" say they either work, or not, and I did test it.

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OK 

 

Hook all to terminal A. If this gives you good voltage everywhere ...throw the diode isolator away and get a solenoid isolator.

Cole Hersee ($$$)makes a smart solenoid isolator, #48530, but it's the best. It will let your 12v converter charge your truck battery.

 

 

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I'll hook it all up and check it tomorrow.

As a matter of fact, I talked to the local RV installer-guy this afternoon, and he told me he hadn't seen a SS isolator in years.

Guess I'm showing my age again. The #48530 is $125 on Amazon, but it looks like it would be money well spent.

Buy the best and only cry once.

Thanks  WME,

BTW, I lived in Dubois for a bit a LONG time ago.

Made it to Riverton and back once in a '57 Ford station wagon. Wish I had that wagon now...

BR,

TG

 

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You wouldn't recognize Dubois, the billionaires have chased all the mere millionaires out of Jackson and the millionaires have all moved to Dubois🙄

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Posted (edited)

OK, so I hook House batty, truck batty and Alternator together on a single post and I get correct Alternator charge voltage of 14.6 V. 

Does this make the case for a bad isolator?

 

On Dubois...

Well I guess Buffalo BBQ weekend,Timberjack Joe and the annual rodeo are goners by now. A friend of mine who was through about a month ago said Welty's General store gave it up after 130 yrs. I used to play weekends at the Ramshorn Inn and my girlfriend worked at the Cowboy Cafe.

Wasn't much there then, wonder if everyone still says "you bet" and "Let'r buck"    ; )

TG

Edited by ToyoGuy
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First things first, yep time for a new isolator. A standard $30 continuous  duty isolator will work just as well as the Cole Hersee unit just not as long of a life span and no smart charge. Full on deep end stuff...https://www.hellroaring.com/

 

Dubois... Cowboy and Ramshorn still on going. Rodeo is Sept... Timber jack Joe is at all the Mountain Man Rendezvous. Welty's is trying to reopen what it will who knows. 

 

The big deal now is the National Museum of Military Vehicles. If it had wheels or tracks it's there

Edited by WME
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I am late to this but I just read through the thread.

 

Voltage goes up when resistance goes up (V=IR). So you have a bad connection somewhere causing high resistance and voltage increase. From the testing that you have done that connection is on the house battery terminal of the isolator, probably the internal contact, but maybe worth cleaning the external connection as it is easy. Maybe check the resistance in the positive line to the house battery from the isolator. I suspect that if you replace the isolator and you will be good IMHO.

 

Edited by neilp
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Thanks neilp,

 

Never hurts to consider all possibilities, for sure.

In my mind, it would seem that, if the over-charge problem disappears completely when House "+" battery connection, Truck "+" battery connection, and Alternator output "+" connection are stacked/connected on (any) single post, (which eliminates the isolator altogether), that the truck "+" battery terminal-to-isolator post wire is clean/good.

That said, I am re-checking everything before I install the new (and different type)  isolator.

 

With the new non-solid state type, I believe I'll have to install a "true ignition source" connection/wire for a single added connection.

Not sure where I'll grab it from yet, gotta consult the FSM or poke around. Or both.

 

I am shopping new isolators now and there's some additional features that I need to understand more about, before I lay down my hard earned weasle-hides on the more expensive offerings.

 

No problem though, I got time while the cushions get re-covered......

Before I visit Dubois ;)

 

BR,

TG

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My head is spinning, the voltage sense is at the alt (or at least  one with out and external regulator) . It relies on the voltage if it's high the field current is reduced doing so reduces the current output. High voltage reduces the field current. What am I missing here? This is a AC generator it relies on the diodes to rectify the AC to usable DC.  

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A common true ignition source for a solenoid isolator is the switched wire for the wiper motor.

 

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3 hours ago, Maineah said:

My head is spinning, the voltage sense is at the alt (or at least  one with out and external regulator) .

Hey Maineah,

This alternator is externally regulated, not sure if that's helpful.

The regulator is new, as is the alternator.

The voltage sensing wire/circuit in the wiring harness that goes to the regulator connector and the connector it attaches to the regulator with have both been cleaned and tested good.

I have also re-tested the whole setup with an extra good regulator, so I believe the new regulator is not the problem.

 

When I wire the isolator out of the system (all battys chg'd) and the system sees both 12V sources as a single one, everything runs/looks right (14.5 V) in voltage output from the new alternator/regulator combo.

I have had solid state isolators fail before, so before I pay someone $200/hr (current hrly auto-electric $-rate here in paradise) to chase this further down the rabbit hole, I'm going to switch to a different style of isolator for $20-$40 bucks.

 

Thanks WME,

Good to know.

 

TG

 

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Your Sunrader came with this exact isolator. I replaced mine once about 10 years ago. Never had a problem with it and my first one, the original, wasn't bad, it was just dirty. After all you've spent maybe this cheap one will be a good choice. 

Tekonsha 7001-S 4 Terminal 12V Continuous Duty Insulated Battery Switch | eBay

Linda S

Yes, I use the extra ground wire in the front. I have the original docs from when mine was made and I installed it same as original. 

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Hey thanks Linda.

Because the original setup seems obviously changed and the main 12V cables from front to back are not well routed and old, I am questioning the #8 gauge Pos and Neg wires installed from the cab to the back of the coach/circuit distribution panel.

For an 18' run it seems like a pretty minimal gauge. Seems like it would be good to change to #4 gauge wire.

Also, I don't see why they ran a ground all the way from the cab / front to the back, when they could just ground to the chassis at the back. :pinch:

I have the luck of having a neighbor who also owns the same year and model SunRader 4x4 as me (how often will that happen?) and I'm going to do some comparison-checking on his system this morning. Maybe I'll get a better picture of what they did originally and what I want to do.

BR,

TG

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