Triumph Trident Electrical Problems


| 10/23/2018 12:06:00 PM


Keith Fellenstein Tech Corner
Editor's note: If you're having trouble with that old Suzuki, BSA, or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith's Garage, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an email with "Keith's Garage" as the subject.

Q: My 1974 Triumph Trident continues to blow the 20-amp fuse located near the battery every time I attempt to kickstart the bike. I have also noticed that the directional lights and brake light don't work. The headlight is working, but I can't switch from low to high beam. Any advice on where one should look for problems?
— Tony Zullo/via email



A: Since it's blowing the fuse when you kickstart it, I'm suspicious that either the rectifier is bad, or the alternator is wired to the rectifier incorrectly. Lift the seat and look for the black multi-plate rectifier. The leads from the alternator should be connected to the left and right connectors. On my 1974 Trident, that's green with yellow stripe on the left, and white with green stripe on the right. Brown/blue is in between, and red is attached to the center top lug. If yours is already like this, then we have to delve further. Disconnect the green/yellow and white/green wires and see if it still blows fuses when kicked. Assuming it doesn't, you then have to test the alternator leads against each other and to ground using a multimeter. There should be small resistance across the alternator leads, and infinite resistance from either of the leads to ground. If that all tests out there is a good chance your regulator is bad. Once you have isolated the fuse blowing problem, you can move on to the indicators and brake. Often the indicator switch is corroded, and they can be tricky to fix. The brake should be easier. For the rear, disconnect the wires leading to the brake switch and jumper the spade connectors with a short piece of wire. If the brake light works now, the switch is bad, which is not uncommon. The front switch gets gummed up by brake fluid leakage, as I just found out when I went out to my '74 to test this answer. Well, that and the rear bulb had vibrated itself to pieces again.

DAVIDP
11/1/2018 11:19:42 PM

With the key on the white wires are hot (negative voltage.) The headlight is on a separate circuit, blue wire, and only on when the switch in the headlight shell is turned on. If only the low beam is available I would suspect the handlebar switch. You can see if the high beam works by pressing the flash push button. My first suspect in your trouble would be the front brake switch. These are goofy nylon things which don't work very well to begin with. Perhaps the white lead to this is shorting to the bars? I always replace these with proper hydraulic brake switches.


DAVIDP
11/1/2018 11:19:41 PM

Do check the rectifier. Seems like I had to replace mine often on my '74 Trident. However, the charging system components are connected at all times. A short there would blow the fuse at all times, even with the switch off. Inspect the rubber buffers under the seat pan. If they are missing or worn down the weight of you on the seat can cause shorting to the seat pan.


DAVIDP
10/27/2018 9:53:20 PM

Do check the rectifier. Seems like I had to replace mine often on my '74 Trident. However, the charging system components are connected at all times. A short there would blow the fuse at all times, even with the switch off. Inspect the rubber buffers under the seat pan. If they are missing or worn down the weight of you on the seat can cause shorting to the seat pan.




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