22R Alternator Not Charging

[Tim86]

Chaps,

1995 22R stock standard (with brospeed)
Bosch alternator, made in S.A.
Battery 100%, trickle charged



When voltage is measured directly at the alternator and the motor is running, battery connected, I get a reading of approx.11-12V. measured across the main output and body. I get 0V when measured across the choke output and body. Motor cuts out when positive is removed from battery.

1) Have I narrowed it down to a shot alternator?
2) What might be shot within?
3) Was the original alternator a Bosch?
4) Once running, should a 22R be able to run without a battery?
5) Can an alternator slowly 'die', i.e. have juuuust enough output to keep motor tickin but not enough to charge?

Many Thanks

[Family_Dog]

More than likely the voltage regulator has died. Replace it and maybe check the alternator bearings as well. One assumes you have checked that the cables around the alternator are tight and in good condition?


-F_D

[Tim86]

Thanks Family Dog, is there any way to test that regulator? I also took the alt out, and the regulator out the alt - bearings seem fine to me. Yes I measured voltage directly across the alt outputs and it's body.

[Family_Dog]

The alternator should provide minimum of ±13.1v when engine is at idle, if not, then it is faulty. Midas should be able to assist you there.


-F_D

[Mud Dog]

Could be that one of the diodes in the diode pack is breaking down. Remember this is alternating current coming off the alternator coils and there are two opposing diodes that each take an opposing pulse direction of the AC and shunt it out as DC ... in other words, a bridge rectifier. If either of these diodes is faulty you will only get ½ the pulse, therefore ½ the voltage. If both are faulty you will get 0 voltage.Typically you should be getting between 13.8V and 14.5V at the battery when the engine is running, and as far as I know the engine should still run if you disconnect /remove a terminal from the battery.

[Tim86]

Judging by google the diode pack looks to be separate from the voltage regulator and rather complex.. Andy do you have to replace the diode pack as a whole? It seems that I should rather take it to be tested before going out to buy parts.

[Mud Dog]

Diode pack is a 'whole' unit as far as I can remember. Better to have it tested, Tim. Could be either the diodes or regulator and you could save a couple of bucks if you don't have to replace both. Either way, replace with OEM or decent quality products - this is the heart of the electrical system and it could be a crappy experience if it lets you down far from home.

[mcw]

Hi Tim

some years ago when i still had my SFA ,also hada problem with alternator not charging ,the problem was traced to a broken circuit in the
instrument cluster . i removed cluster and had a auto electrician fix the circuit ,charging problem solved

Martin

[Tim86]

Thanks for the feedback guys - I have finally got it solved.

Truck died, pulled alt, pulled alt apart, tested everything except voltage regulator as that's doable but a bit more tricky. Pulled unused auxillary battery isolator out for good. Bought VR and put all back in - nothing. Pulled apart alt, bought new much more better digital multimeter, tested everything, put back together and took to be tested - charging 100%. Put back in truck - nothing.

Had a little cry.

Thought a bit, jumped a positive wire from battery to alt charging light wire - spooled up immediately and charged away. Replaced aux battery isolator system and alt charges fine.

Installation of the isolator required mods to the alt itself with different connections etc. Without the isolator the alt didn't get exciter current from battery or whatever, reversed all mods by feel, chucked isolator and got a reasonable 13.82V at battery. The new VR was required though as the old had given in.

Pulled alt, diode mod and only get an increase from 13.82 to 13.98V at the battery:/ Why would this be the case?

Martin, out of interest this whole performance took place without the cluster display connected at all as my interior is currently stripped... food for thought

[Tim86]

Chaps, can anyone tell me which is the correct diode to use (1N4007 or 1N5402) for the alternator diode mod?? I see that two types have been referred to on this forum. I used the 1N5402 and only got an increased charge voltage of 0.16V - I need about a 1V increase...

[mcw]

Hi Tim
Not very good with electrics ,i also had alternator at a auto electrician ,they could not find any faults on system
Read on overseas forum about cluster problem ,took it to auto electrician and after their repair,charging system worked fine

Martin

[Family_Dog]

The only difference between those two diodes is that the first can work with a voltage up to 1000v at 1 amp, while the second one is a 3 amp diode rated at 200v. I don't know where the diode is fitted, presumably in the 'ground' (or negative) lead of the VR? When forward biased, both these diodes will have a voltage drop of 0.6v over it, thus a 13.8v VR should probably now give 14.4v aggregate.


-F_D

[Tim86]

Yes, fitted inline on the VR negative lead as per Cassie, shown below. I was expecting about a 0.5V increase but only got 0.16. It was a new VR that I put in stock, tested the voltage, took it out, modified it and re-tested it. I trust that I have the bias correct with the black end connected to the VR and the silver end to ground. Maybe the new VR hasn't been 'run in' adequately yet.

17102010643.jpg (18.1 KiB) Viewed 5437 times

[Family_Dog]

Yep, if it was wired incorrectly, it would not work at all. Probably do all sorts of horrible things to your vehicle electrics as well.

Please post the link to Cassie's original article if you still have it.


-F_D

[Family_Dog]

Apparently the diode has to be in the voltage sensor lead. I'm not au fait with car electrics but seems what people do is to remove the voltage sensor fuse and replace it with a diode, thereby gaining ±0.6v over & above the nominal voltage. Some people have put two diodes in thereby effecting a 1.2v increasi in charge voltage, but I do not recommend that - could lead to expensive repairs of other electrics.

https://www.youtube.com/watch?v=Dp7J083exKw


-F_D

[Tim86]

viewtopic.php?f=14&t=14716

http://hilux4x4.co.za/views/viewtopic.php?f=3&t=11636

[The Legend]

Take a 16 mm wire direct from the alternator to the battery and check your charging rate again.

[Tim86]

Hi guys

Recently my dash battery light has begun to keep showing after startup. It continues to do so until the revs go past 1300 after which it goes out. On return to idle the light does not come back on.
Battery holds a charge of 12.10V.
On startup, below 1300rpm, charging system reads 12.10V.
Once revved past 1300rpm, charging system reads 14.5V.
Return to idle, system reads above 14V.
Cut the engine, startup again, and the same scenario ensues.
Alternator bearings and voltage regulator/bushes replaced 8000km ago (diode pack not replaced).
Alternator also had diode mod added 8000km ago as per the above thread.

It seems that the alternator is not receiving any excitor current until you give it a little nudge past 1300rpm.
Is this acceptable or should I be worried, and what could be the reason?

Thanks!

[Tim86]

Hi Chaps

Any answers as to the above query?

Thanks

[dax021]

Might be a dumb question, but have you blown out the brush area (commutator?) with air. Maybe old graphite dust from the old brushes interfering. I'm no auto leccie, but this is something I would check. Other than that, I wouldn't worry to much. Carry a spare for just in case. I bought an 80A alt from my local spares shop for less than R1K. If you like, you are welcome to my old original alt which is electrically perfect, but one of the mounting "ears" have broken off from overtightening. Only problem is that I'm in Plett, so you'll have to make a plan to get it to you.

[dax021]

Oh crap, just noticed you have a 22R and mine is 4Y. Not sure if it will help.