MF240 Charge warning light always on

[agdodge4x4]

Never noticed this before because I dont use the tractor at night. However tongint I noticed the light is on at all rpms. No other warning lights are on. This is about a 1986 mode or so. Anyway, how can I troubleshoot the cause? Also, how can I make sure all of my other warning lights are working ??

 

[agdodge4x4]

Obviously the likely answer is the alternator is bad but Id like to verify that before rebuilding or throwing parts at it. I just dont know how.

 

[MF#1]

Well I see you got it running, how?
I just finished fixing my Dad's 255 that kept running the battery down. Found the heavy wire from the alternator to the amp gauge had shorted out, spliced it back in and worked fine. If you put a volt meter across the battery while running you should see about 14 volts or so, that will tell you if the alternator is working. I would say to check all of your wires from the alternator and be sure they are connected, the 255 had vibrated the nut on the amp meter loose also. If your lucky it "might" be a bad connection.

 

[Jim.ME]

(quoted from post at 22:55:57 11/23/20)
Obviously the likely answer is the alternator is bad but Id like to verify that before rebuilding or throwing parts at it. I just dont know how.

Warning lights usually come on when the key is on without the engine running. Some equipment have a momentary switch to test warning light bulbs.

Depending on the alternator, some of those can be full fielded to test output, such as some Delcos have a tab in a hole in the rear of the housing you ground to get full output. Given it appears there were several models of the 240 and they used different alternators, I can't say which one you have or how to test it. I would suggest the service manual for your tractor should give you diagnostic procedures. I have to ask. If you don't know how to test it for output, do you know how to test the components in it to see what failed and needs replacement? You will just be throwing parts at it if you don't know how to test the components or have a manual to guide you. You may want to consider taking it off and having it tested, then swap it out if it is bad. Depending on the alternator part could cost almost as much as an exchange unit.

Have you checked all the wires attaching to the alternator for function? Have you checked voltage with it running to see if the light might be bad?

 

[agdodge4x4]

I have no idea how to test compenets of the alternator but if the tractor is running and my battery is sitting at 12V then I know there is an issue with the alternator in general or a wire from it to the battery. Yes??

 

[Jim.ME]

Yes, you are correct the voltage staying a 12 volts while the engine is running is an indication of a problem with the charging system. I say that is correct as long as you have increased the engine RPMs (to half throttle) for a few seconds to see if the alternator starts charging at a higher RPM. Many alternators will not start charging at low rpms.

If you can confirm the wiring to the alternator is correct and functioning, I would suggest you remove the alternator and have it tested at a shop. Do you know what brand your alternator is and if it is externally or internally regulated?

Do you have the correct Massey Ferguson Operator's Manual and Service Manual for your tractor? I ask about both manuals as MF put the wiring diagrams for some in the Operator's Manual and the technical diagnosis and repair info in the Service Manual. I don't know if they did that for the 240 manuals or not. If you do not have the manuals, I expect you will not find those manuals as free pdf files, likely purchase will be required.

 

[2tractors]

Loose belt???

 

[agdodge4x4]

Ok. So the light was not on this morning. All of my warning lights seem to be non functional. My headlights and dash lights work fine. I test my oil sender and I have continuity from the oil sender to the light but it does not illuminate when 12v is applied to the wire.

Does this tractor have separate grounds for warning lights ? If so, where is it?

 

[agdodge4x4]

Also, battery sits at 12.5v when running at speed. The alternator light did illuminate but so dimly that I had to
Remove it from the back of the cluster to see.

This still seems like a bad ground foe my warning lights and a bad alternator for the charge issue.

 

[Jim.ME]

(quoted from post at 14:07:42 11/24/20)
Also, battery sits at 12.5v when running at speed. The alternator light did illuminate but so dimly that I had to
Remove it from the back of the cluster to see.

This still seems like a bad ground foe my warning lights and a bad alternator for the charge issue.

Again, do you have the manuals so you can look at a wiring diagram? Do you know what you have for an alternator and if it is internally or externally regulated?

It is likely the warning indicator lights would have power any time the switch is on and the senders for them control the ground side. So the wire between the sender and switch can have continuity and the light will not work if you apply power - try grounding the wires at each send point.

Head and dash lights should have nothing to do with warning lights.

Yes if the battery voltage stays at 12.5 volts while running at speed you have a charging system problem. If the wiring is correct (and if has an external regulator that is working) the alternator has likely failed.

 

[agdodge4x4]

Alternator is a Lucas 24123B.

Looks to be internally regulated. Either way, the connector is corroded to pieces. So I need to get the alternator rebuilt along with some new connectors and well go from there. Wondering if the alternator has something to do with ground.

I dont have a service manual other than an aftermarket one. Ill look for wiring. The ending units may be grounded but there are two wires as the warning light side foe the bulb and there is no continuity between any green ground wires and the battery negative. Those wires are tied together at a ground somewhere that must not be good. Wiring harness looks good and all wires are supple.

Lets get the alternator issue figured out first and Ill be back.