Red light in MKII Carrier

[rob love]

It could be as simple as the brushes are worn or dirty. If that is the kind of work you can do, then you will have to pull it off. If not, then you will have to pull it off and send it to an automotive electronics place. Best to find one that has been around for a long time. They likely do not run into a lot of 3 brush generators these days.

[Bruce Parker (RIP)]

Originally Posted by rob love

It could be as simple as the brushes are worn or dirty. If that is the kind of work you can do, then you will have to pull it off. If not, then you will have to pull it off and send it to an automotive electronics place. Best to find one that has been around for a long time. They likely do not run into a lot of 3 brush generators these days.

Agreed, generators and starters either work or are made to work with a little cleaning and work on the brushes. If it is a catastrophic failure in the windings then you need professional help (or at least I do). Usually a quick look inside will tell you if there's a short, burning or something stuck.

A steady 6V reading (assuming what you are checking connects back to the battery) strongly suggests to me it's the generator not putting anything out.

What's that old trick about reversing the terminals on a generator to make it 'motor' as a way of checking it?

Pulling a carrier generator would be easy enough it it weren't for that friggin fan. You pretty much have to remove it or risk driving one on the blades into the radiator cooling fins. If you do remove the fan first (recommended) then you scrape every bit of skin off your knuckles working the 7/16' wrench between the fan extension and the aforementioned rad cooling fins.

[rob love]

There are simple tests you can do with a multimeter once you have the generator apart and on the bench. Continuity between all of the segments is one of them. Ensuring the windings are not going to ground is another. Then there is flashing of the generator once it is together. In fact, that is something that can be done with it in place on the vehicle and the cut-off disconnected before you take it off. I would have to read up on the third brush type generators though. You need some level of residual magnetism for a generator to work.



If all this is lost on you, then remove it and take it to an automotive shop. They can also put the armature on a growler which instantly tells them if there is a problem. The average home mechanic does not have a growler. I may well be living in the past thinking the automotive shops have them anymore.

[Ron Pier]

The trick I've used many times on my 6V motorcycle dynamos to test them is:-

Take the two wires that come out the dynamo F&D, connect them together and connect them to the live end of a single filament bulb (12V is best for this purpose) Earth the cap of the bulb to the dynamo with crocodile clips and run the engine. The bulb should light up and glow brighter as you rev it up. If it doesn't, As already suggested, check/replace the brushes, clean up the end of the commutator with thinners/switch cleaner etc. The build up of carbon dust and shite can insulate the commutator and or cause the brushes to stick up in their holders.

By the same system you can test/motor the dynamo on the vice by connecting those two same joined wires to the poss of a battery and earth the body to the neg side. The dynamo should motor in the same direction that it charges at.

I've said an awful lot here for what is a very simple test operation. Ron

[charlie fitton]

Have you checked the cut-out relay?

[Robert Bergeron]

Thank you Bruce , Rob, Ron & Charlie . All very good and most generous advice . All that know me more intimately know what my trade was for 32 years in the service and it was not REME like my father . Charlie , what does that relay look like and where is it located ? Picture ? I will look at the relay before skinning my knukles as Bruce so explicitly described ang bringing the generator to a specialised shop ....Ahahaaaa, thanks Bruce .

[Robert Bergeron]

Here are pictures of my new cutoff and surrounding wires.Is the cutoff relay the blue «*thingy « to the left of the top picture ? What is the relay’s purpose and what is the description so i can order a new one please ? Many , many thanks .