1984 MF 240 electrical warning light stays on.

Warning light stays on ( lightning bolt). Pulled and had alternator tested, was good. Any ideas would be appreciated
Roy

What alternator? Internal regulator? That sounds like a wiring problem in the excite circuit since you had the alternator checked. The light being on would indicate it is receiving power from the switch. First you need to check to see if the alternator is receiving power to excite it. If not, the wire would appear be grounded somewhere between the indicator light and alternator. It would normally ground through the alternator. The light goes out when the alternator starts charging supplying power to the location the light uses for a ground cancelling the ground for the light. Do you have a manual with a wiring diagram to aid you in which wire is which?

Hello Roy welcome to YT! I would post if the alternator
has a separate regulator, but the AGCO parts book is a
bit tricky. I find a Lighting section but none for
Electrical. And there are multiple models that I cannot
decipher, he says it is an 84 so it is below SN 557882.
AGCO parts book

Based on Roy posting that it is a 1984, it should use the " MF 240 TRACTOR, |-> 522354 ->| A20286 (GB) - 819701 parts book. That book shows 3 alternator options, two Lucas and one Valeo. The regulators are internal or mounted externally on the alternator. The regulators show as different for all three. Things get changed over the years, so it seems best to ask what it has. I asked what I did to get a better idea of what it actually has. An alternator, shown in the book, might have been swapped for a different brand like a Delco type, one or three wire given the lack of love many seem to have for Lucas electrical components.

ROY,
Was the regulator tested with the alternator, or did they only full field the alternator to see that it could charge? The regulator should have been tested with the alternator, so could be confirmed the alternator works via the proper connections to the alternator and regulator. If the regulator was not included in the test, it could be bad.

Here is a link to the parts book. There is an Electrical Equipment drawing on page 15. The breakdowns of the three OEM supplied alternators are on pages 20, 21, and 22.

https://parts.agcocorp.com/en_US/ap...+TRACTOR,+|->+522354+->|+A20286+(GB)+-+819701

Thanks guys, I'll check the alternator/regulator configuration and type this weekend. I do have the service manual and will see if it may be helpful .
Thanks again
Roy

(quoted from post at 19:41:23 12/19/22)
Thanks guys, I'll check the alternator/regulator configuration and type this weekend. I do have the service manual and will see if it may be helpful .
Thanks again
Roy

Click to expand...

Check your service manual but for some reason Massey Ferguson often only put the wiring diagrams in the Operator's Manual, not in the service manuals.

A couple things to check:

Does the charge light come on with the ignition on and engine off? It should.

Does the light come on only with the engine running and up to speed?

Are any other electric powered gauges or indicator lights not working that failed at the same time?

If that is happening, check the power to the instrument cluster. Could be a bad fuse or bad connection.

Most charging systems will not work without that feed back signal from the indicator light, so it may
not be charging if that circuit is dead.

Yes, the light comes on with ignition on and engine off. Then stays on after engine is running, however does seem a bit dimmer at that point. All other lights and gauges are working correctly.

(quoted from post at 15:37:58 12/20/22) Yes, the light comes on with ignition on and engine off. Then stays on after engine is running, however does seem a bit dimmer at that point. All other lights and gauges are working correctly.

Click to expand...

hat alternator is on that tractor? My MF has Delco 10-SI and with it, it would still charge if one or two of excite diodes failed, but the light would probably act just as you describe...the bright & dimmer action.

I'll check the particulars of alternator / regulator this weekend.