headlight relay electrical short in 82 XJ550

Yamaha service manual shows the headlight relay under the rear of the fuel tank (It is sometimes wrong!)

Check to make sure you have the correct relay- the wires to it should be white, black, red w/yellow stripe, blue w/black stripe.

 

To test the wires to make sure they're okay, the Red/Yellow wire should have battery voltage on it when the ignition switch is turned on. The White wire should have voltage (varies with engine speed while cranking) when you're cranking the engine or after the bike starts. If you jumper battery voltage to the Blue/Black wire, the headlight should come on. The Black wire should have continuity to ground. Test that with an Ohm Meter or hook a test light between the Black wire and the Red/Yellow wire and then turn the ignition switch on. The test light should come on. If all of that checks out, the relay is probably bad.

 

Just went and looked. Headlight relay is under LH side cover just above the chain box.

 

A hah! I'm 99% sure that's the relay I swapped the sidestand relay with. That would explain things a bit. I'll check the wiring later tonight and get back to you all. Thanks a bunch - I think we're close to solving this riddle!

 

OK, latest update here. I tried replacing the relay down where the actual headlight relay is, with no luck. Then, on a hunch, I decided I try swapping fuses, just in case there was something off there. I swapped the main fuse with the headlight fuse, and the bike started up fine. But now, even if I have the key out of the bike, the neutral indicator light remains on when it's in neutral, and it'll start without the key in. Oh, and the headlight won't come on .

I take it there's an ignition relay problem? And is it time to upgrade the problem from "headlight relay" to "electrical"?

 

I'm wondering if you've got the safety relay swapped with another.

 

I don't think so. I didn't touch it when I was swapping stuff out last, unless it's been a problem all along, but everything worked fine until I dropped the bike a couple months back.

 

If you apply the brake, does the brake light come on with the key out of the bike?

 

What is the normal voltage level on the "signal" circuit to the headlight relay on a Seca 650 once the engine is up and running? I see from the wiring diagram that the signal starts out as AC straight off the alternator.......is it converted to DC before going to the headlight relay?

Thanks,

Kevin

 

I installed a new headlight relay but I am having problems still. The headlight is off before starting, but it never comes on after the engine is running. Now I am not sure whether the relay is the problem or not.

Are there "specs" I can test with a volt meter? There are 4 wires: Black, White, Red with Yellow stripe, Blue with Black stripe. What kind of voltage should show up across which two wires when the engine is running. If I touch which two wire to turn on the headlight at all times and bypass the relay (to test that lamp is not burned out). Reading schematics is not my forte.

Thanks,
JT
XJ550 1982

 

You can check the headlight using an ohmeter. There should be three terminals coming off the heradlight. Put your meter on ohms and touch the leads together. You should read 0 ohms(short). No put one lead on the center pole on the light and the other lead on one of the other 2 poles. Your meter will either read infinity( the filament is bad) or a near short(the filament is good).

Check again from the centert pole to the other connector.

Before you do this just flip the high beam switch and fire it up. There arer 2 filaments inside the lamp. Chances are only one would be bad. But not always

 

Thanks wamaxim,

I followed your advice, and the headlight is fine. It took off the connector to the headlight relay, and jumped the striped wires, and the headlight came on. Therefore, I tested the voltage across the black and white wires, which must energize the relay. Before my 82 XJ550 was started, the voltage was zero. After my bike was started and running (yeah baby!) the voltage was still zero. This does not prove the relay is good, but I would bet the farm on it that it is since Chacal tested it. Therefore the circuitry on the black and white wires is failing.

What decides and then supplies voltage to the black and white wires after starting? How would I debug it?

JT

 

In the Yamaha manual, in Chapter 6, there is a much clearer schematic. The headlight relay has a diode in the relay itself (btw: sidestand relay does not). Which loops back and latches on the current, as everyone has been describing.

Since I am not getting current on the white wire, and according to the circuit diagram, the white wire is a straight shot into generator with one diode along the way, and this diode is located in the headlight bucket in the diode block. White wire IN and white wire OUT from the diode block should show current. Diode should also show different resistance each way, maybe the manual provides those numbers?

Off to find out. Hope this helps the next guy.

 

I think my diode is shot. Can anyone get a reading?

1. Open the headlight bucket.
2. Disconnect the diode block, look at connector terminals, with casing notch up.
3. Measure ohms from the center terminal to the lower right terminal. According to my calculations, these are the White wire and White/Green stripe wires, and they connect to the two white wires on the mating connector which go to the headlight relay white wire.
4. Reverse polarity.

I am getting infinite resistance both ways. I tried all possibilities from center term to any other, both polarities, and Nothing.

I can get a zero ohm reading on other terminals.

Is my diode shot? Or is this a normal reading?

 

The Clymer manual for the XJ550 models says to test the diode block in
this manner (strangely, it makes no mention of the diode
in the 1981-83 section, but only in the 1984-later models
addendum):

a) Set ohms scale to r x 1

b) Test as follows:

Red (+) lead from tester on: Green wire
Black (-) lead from tester on: Blue wire with white stripe
Result should be: 0 ohms

Red (+) lead from tester on: Blue wire with white stripe
Black (-) lead from tester on: Green wire
Result should be: infinity



Red (+) lead from tester on: White wire with green stripe
Black (-) lead from tester on: Solid white wire
Result should be: 0 ohms

Red (+) lead from tester on: Solid white wire
Black (-) lead from tester on: White wire with green stripe
Result should be: infinity



Red (+) lead from tester on: Yellow wire
Black (-) lead from tester on: Light blue wire
Result should be: 0 ohms

Red (+) lead from tester on: Light blue wire
Black (-) lead from tester on: Yellow wire
Result should be: infinity



Red (+) lead from tester on: Green wire
Black (-) lead from tester on: Black wire with red stripe
Result should be: 8.2 ohms

 

It was the diode block! The headlight relay system now works perfectly. When you nail the problem, that makes it all worth it.

 

Nice job, it feels good.

 

Who loves ya', baby?

 

Chacal, you are da man!