Massy 390 alternator

[Goldmember2000]

Hi folks
Just replaced a 16 year old alternator with and exact copy , all wired up correctly but no charge coming from alternator to battery ?
this was the previous problem so I’m now wondering if alternator was not the problem.
Fan belt checked
No visual damage positive wire or connections
Continuity is 7.00 so something going on with positive run , any ideas of what to check first ?
Many thanks

 

[defender]

Does the ignition light come on ?
A blown bulb will stop it charging

 

[Dry Rot]

If you value your sanity, hire in an auto electrician!

 

[dee]

Check that all the wires are on your starter. The main supply for the alternator is fed of it.

 

[Goldmember2000]

Check that all the wires are on your starter. The main supply for the alternator is fed of it.

Thanks I shall look at starter connections

 

[Goldmember2000]

If you value your sanity, hire in an auto electrician!

Haha that’s why I’m on here talking to you experts

 

[Goldmember2000]

Does the ignition light come on ?
A blown bulb will stop it charging

I’ve got a few lights off on the dashboard so that is a very good suggestion , I shall have a look tomorrow thanks

 

[MF-ANDY]

Check alternator light comes on when it should. Test for 12v at small alternator wire with ignition on and permanent 12v at large alternator wire.

 

[Goldmember2000]

Check alternator light comes on when it should. Test for 12v at small alternator wire with ignition on and permanent 12v at large alternator wire.
[/QUOTE

 

[Goldmember2000]

Does the ignition light come on ?
A blown bulb will stop it charging

The only lights that come on are oil, battery , both turn off when engine starts

 

[Mr Mackay]

I have a CX 105. Had the alternator light come on slightly ,or in other words ,not go off completely . The tractor was always a bad one for starting
Changed for new alternator ,(Iskra) same fault still showed as the old one ,so just left it on ,while in the meantime I bought a new rectifier pack for the old one and a regulator .
Fitted both parts , and put it on shelf for a spare .
Spent a fair bit ,checking earths ,fitting new battery positive , battery , still a pig in the cold weather ,but on test always showed good voltage ??

My son put the spare alternator on (without my knowledge )and the light went out completely !!
Heavy duty battery Varta as well , and shes better than shes ever been
I suspect the new one was faulty too in some way but because it was new didnt suspect it !

Very unlikely your fault too , but just thought I would mention it !!
Is there a fuse gone maybe , or ignition switch fault ,but the test for 12 v at the small wire on the starter solenoid would tell you ,as mentioned .

The other thing is , after the tractor has been sitting for a good while ,maybe first thing in morning check battery voltage - a good battery is around 12.6- 12 75 I would say .It may be lower because its not been charging properly ,but certainly 12 .45 at least .
Whatever it is , start the tractor and watch the voltage . You say the battery light goes off ,??? if so It should be charging to some extent (its the increasing voltage that turns off the resistance in the battery light )
Check if the voltage then climbs above the standing charge you first measured

 

[Wisconsonian]

the battery light comes on with the engine not running, that means the bulb is not burned out, and the alternator is drawing some excite current, then the light goes off with engine running so the alternator is no longer drawing current. What voltage are you getting at the terminals running?

 

[Goldmember2000]

I have a CX 105. Had the alternator light come on slightly ,or in other words ,not go off completely . The tractor was always a bad one for starting
Changed for new alternator ,(Iskra) same fault still showed as the old one ,so just left it on ,while in the meantime I bought a new rectifier pack for the old one and a regulator .
Fitted both parts , and put it on shelf for a spare .
Spent a fair bit ,checking earths ,fitting new battery positive , battery , still a pig in the cold weather ,but on test always showed good voltage ??

My son put the spare alternator on (without my knowledge )and the light went out completely !!
Heavy duty battery Varta as well , and shes better than shes ever been
I suspect the new one was faulty too in some way but because it was new didnt suspect it !

Very unlikely your fault too , but just thought I would mention it !!
Is there a fuse gone maybe , or ignition switch fault ,but the test for 12 v at the small wire on the starter solenoid would tell you ,as mentioned .

The other thing is , after the tractor has been sitting for a good while ,maybe first thing in morning check battery voltage - a good battery is around 12.6- 12 75 I would say .It may be lower because its not been charging properly ,but certainly 12 .45 at least .
Whatever it is , start the tractor and watch the voltage . You say the battery light goes off ,??? if so It should be charging to some extent (its the increasing voltage that turns off the resistance in the battery light )
Check if the voltage then climbs above the standing charge you first measured

Thanks for the reply, it’s a brand new alternator and battery , I assumed the battery light on the dash going out on if toon was normal ?
the voltage on battery is 13 when tractor is off and 12.45 when engine running high or low,
testers directly on alternator indicate power being produced and I can certainly hear it wizzing round .
Fuse box is all okay, currently trying to get dash off as I know some bulbs have failed in there and due to check starter motor connections.

 

[Mr Mackay]

Thanks for the reply, it’s a brand new alternator and battery , I assumed the battery light on the dash going out on if toon was normal ?
the voltage on battery is 13 when tractor is off and 12.45 when engine running high or low,
testers directly on alternator indicate power being produced and I can certainly hear it wizzing round .
Fuse box is all okay, currently trying to get dash off as I know some bulbs have failed in there and due to check starter motor connections.

The battery is a good one if its at 13 standing.
The alternator cannot be outputtting any charge is the voltage drops to 12.45 when running - I assume the lower voltage is due to the power used to start it !

 

[manhill]

I learned the hard way to also check that the casing of the alternator is getting a good earth via the mounting bolts.

 

[Wisconsonian]

What is the voltage on those alternator terminals when running, measured to the alternator case? if you don't have a cable drive tachometer, then one of the wires may be AC, so that one doesn't matter.

 

[ACEngineering]

Hi folks
Just replaced a 16 year old alternator with and exact copy , all wired up correctly but no charge coming from alternator to battery ?
this was the previous problem so I’m now wondering if alternator was not the problem.
Fan belt checked
No visual damage positive wire or connections
Continuity is 7.00 so something going on with positive run , any ideas of what to check first ?
Many thanks

Was it a vapormatic VPF4015 alternator by any chance?

Had one of them do that couple weeks ago!

 

[Goldmember2000]

I have a CX 105. Had the alternator light come on slightly ,or in other words ,not go off completely . The tractor was always a bad one for starting
Changed for new alternator ,(Iskra) same fault still showed as the old one ,so just left it on ,while in the meantime I bought a new rectifier pack for the old one and a regulator .
Fitted both parts , and put it on shelf for a spare .
Spent a fair bit ,checking earths ,fitting new battery positive , battery , still a pig in the cold weather ,but on test always showed good voltage ??

My son put the spare alternator on (without my knowledge )and the light went out completely !!
Heavy duty battery Varta as well , and shes better than shes ever been
I suspect the new one was faulty too in some way but because it was new didnt suspect it !

Very unlikely your fault too , but just thought I would mention it !!
Is there a fuse gone maybe , or ignition switch fault ,but the test for 12 v at the small wire on the starter solenoid would tell you ,as mentioned .

The other thing is , after the tractor has been sitting for a good while ,maybe first thing in morning check battery voltage - a good battery is around 12.6- 12 75 I would say .It may be lower because its not been charging properly ,but certainly 12 .45 at least .
Whatever it is , start the tractor and watch the voltage . You say the battery light goes off ,??? if so It should be charging to some extent (its the increasing voltage that turns off the resistance in the battery light )
Check if the voltage then climbs above the standing charge you first measured

Thanks for the reply, it’s a brand new alternator and battery , the voltage on battery is 13 when tractor is off and 12.45 when engine running high or low,

The battery is a good one if its at 13 standing.
The alternator cannot be outputtting any charge is the voltage drops to 12.45 when running - I assume the lower voltage is due to the power used to start it !

That’s right my friend , I’m going to check starter cables, bulbs in dash next

What is the voltage on those alternator terminals when running, measured to the alternator case? if you don't have a cable drive tachometer, then one of the wires may be AC, so that one doesn't matter.

20 volts coming out of alternator positive

 

[Goldmember2000]

Was it a vapormatic VPF4015 alternator by any chance?

Had one of them do that couple weeks ago!

It was a Lucas 15 years old so it had a good run

I learned the hard way to also check that the casing of the alternator is getting a good earth via the mounting bolts.

actually that’s a very good point , I didn’t think to clean the mounts , thanks !

 

[ACEngineering]

It was a Lucas 15 years old so it had a good run

actually that’s a very good point , I didn’t think to clean the mounts , thanks !

No I meant was the replacement a vapormatic one not original.