Mahindra 3505 DI Alternator Issue

[mmiker]

I have seen similar posts, so thanks for any thoughts on my particular issue. I have a 2003 Mahindra 3505-DI. New to me. Day after I bought it, it would not start - battery was dead. After some time on the charger, it started right up. However, it died again a week later. Jumped it and tested the Voltage at the battery and the alternator. Both showed about the same 12 volts (slowly declining). I figured the alternator was bad, so ordered a new one and installed it the other day. Charged the battery and started the tractor. Voltage showed the same 12 volts at the battery and the alternator. In theory the new alternator could be bad, but figured there is a slim chance of that. Since the battery and alternator are both reading roughly the same voltage, i am presuming the wiring from the alternator through the starter to the battery are good.

In reading other posts, an 'exciter wire' is referenced. I am wondering if there is something wrong with this part of the system. I called a Mahindra dealer and they provided the attached wiring diagram. I highlighted the relevant wires: one to the battery, one to the ground and looks like the third wire goes to the instrument panel ampmeter. I do note that when i start the tractor, the ampmeter goes negative a little and then back to center. So I am guessing there is connection to the alternator? Is this wire the exciter wire? Any way to test it?

I am not that mechanical of a person so hoping somebody more experienced can give me a suggestion as to how to troubleshoot before I start pulling the firewall off.

Thanks for any comments or suggestions.

 

[Stimw]

It is common to use an idiot light for the exciter circuit.
The schematic shows a fuse between alt and starter/battery connection.
Have you checked voltage at alt output/large terminal?

 

[radios1]

I'd just modify the brackets to accept a leece-neville alternator, and call it much better!..

 

[Fuddy1952]

The alternator exciter wire it shows going to instrument cluster. My guess is that's where the problem is. Shame they don't show a schematic of the cluster, maybe that's where a voltage regulator is?
If it's not hard to get to (back of cluster) unhook battery and trace that wire to see.

 

[stevem5215]

Looks to me like the Alternator has a build in V regulator. A three wire just sends a Battery reference voltage to the Alternator.
Do you have 12v on your two connections ? And is the ground wire good ? If no 12v on the third terminal that's where I'd start looking. Use a meter. Not a light. If you are only getting 12V out of the alternator then you are not charging at all.

Steve with a GM727 alternator on a Jinma Tractor instead of that Chinese low quality alt & VR setup.

 

[WranglerX]

First I am not sure the 3525 wiring diagram is correct for you 3505 if you say you have ammeter... There is no ammeter on the 3525 diagram...

If the 3525 wiring diagram is correct for your tractor.....

IF you turn key on, you should see "ALT" lamp lit.... As alternator spins up lamp should go out....

Have you tester maxi-fuse on alternator output to starter/battery to see if good?

IF fuse is good...

IF ALT lamp does not light when key turned to "on" it may have bad bulb, and alternator is not getting special shot of ground through bulb to initialize charge sequence.... Instrument cluster diagram indicate there is a ground standing on one side of all lamps in instrument cluster and power (12 volts) to light any lamp in instrument cluster comes in from external....

You should see about 13.8 to 14.2 volts DC output at alternator B+ terminal if alternator is functioning ....

Unfortunately for people trying to read wiring diagram actual designations on alternator are blanked out, but I am going on premise the wire going to starter (then to battery) is labeled as B+ and the wire going to instrument cluster is unknown as it covered by highlight. And it indicates to me in wiring diagram the circle with "X' in middle is a LAMP (could be volt meter but I doubt it)...... And be sure ground wire from alternator to chassis or engine block is good.....Not sure where you are seeing ammeter.... Ammeters went out of style many long years ago when alternators first appeared in 70's...

Only gauges I am seeing in"instrument cluster" (wiring diagram) is engine temp gauge and fuel level gauge....

Dale

 

[BobG_in_VA]

If your gauge needle is sitting in the middle...you aren't getting any charge...ie. nothing. Try this (as far as exciter), get it started and then turn on the lights...if the needle goes negative, you have a problem, it may make the unit start to charge though..if so when you start it from now on, that's how you get it charge...I had that problem on my '67 135 Massey, (it has a generator vice alternator) I fiddled with a voltmeter and the voltage regulator for about 2 hours and finally got what I want...good luck...let us know.. BobG in VA

 

[mmiker]

All - thank you for the replies and suggestions. I apologize for the slow reply as I had been on the road. I will be working on the tractor this weekend and will post updates and more information on the trouble shooting. Hopefully find the culprit. More to come.....

 

[davidgreams]

You can certainly get an alternator put in for less than $1200. Call around to local non franchise mechanics with your Year/Make/Model and ask how much to install a new alternator. If you have a mechanically inclined friend ask them to help and buy an alternator at a parts store.

No need to junk a car for an alternator, stay green and keep it moving.

 

[WranglerX]

You can certainly get an alternator put in for less than $1200. Call around to local non franchise mechanics with your Year/Make/Model and ask how much to install a new alternator. If you have a mechanically inclined friend ask them to help and buy an alternator at a parts store.

No need to junk a car for an alternator, stay green and keep it moving.