Why does my oil light flash with turn signal

[mlew]

I just got a nice 79SF and the last thing to fix is the turn signals. They work just fine except the oil and headlight pilot bulbs flash with the signals. The signal bulb never comes on but is always very dimly lit.
I have checked the wiring in the headlight bucket and it all in the right place according to the wiring diagram. Everything else on the bike works fine.
In comparison to my 80SG:
The oil light does not come on with the ignition or any other time.
The headlight warning light does not come on when the headlight is unplugged.

Anybody ever seen this one before?
Got any ideas an what to look at next?

[vedgar]

poor grounds

check the black wire grounds. They are usually the culprit

[MaximPhil]

check the black wire grounds. They are usually the culprit

+1 on that. Certainly the headlight blue light being on but dim but also check the low beam filament is not blownin the bulb as the reserve light module is in that circuit too. This is scary I am answering electrical questions
The quest for clean grounds continues on mine.
Phil

[bikerphil]

May want to try bypassing the Light Checker Unit (79SF only) under the left side cover, jump the blu and blu/yel wires together in the harness plug after unplugging it. I have seen the round type pins in the connector getting loose and causing problems.

Could also try bypassing the RLU

[mlew]

Bypassed the RLU and light checker modules, cleaned and checked grounds. Even ran a wire from battery negative to harness ground at the VR. Installed a new fuse block.
No change.
High and low beam work as does the high beam indacator in the tach.

Anyone have a pdf wiring diagram for a 1979SF?

I'll keep trying

[bikerphil]

Not sure where they are but aren't there a couple of diodes somewhere in the wiring which permits the use of a single flasher light in the pilot box? The 79SF wiring diagram does not show it, it shows a two bulb setup in the pilot box like the 80-81 uses.

[mlew]

I noticed that too Phil. Is the single turn signal indicator bulb in the pilot box correct for a 79SF? Or should it be a double like my 80SG?
I'll look for a diode tonight. Is it made into the wiring harness? Any idea where it might be?

[mlew]

All of the wiring diagrams I can find show the two bulb indicator pilot box. None have the single bulb turn signal.
Any one have a diagram that shows the single bulb pilot box?

[bikerphil]

I noticed that too Phil. Is the single turn signal indicator bulb in the pilot box correct for a 79SF? Or should it be a double like my 80SG?
I'll look for a diode tonight. Is it made into the wiring harness? Any idea where it might be?

Yes, the single indicator is correct for a 79SF. I don't know where the diode (if there is one) is located, I have always wondered. Every schematic I've ever seen has the dual type pilot box.

Edit: after looking at an XS650 diagram which does have the single bulb signal box, it shows no diode in the circuit.

[bikerphil]

The way I understand it, with the single pilot box indicator, the diode would only be necessary with the use of LED bulbs. Any chance that the PO changed any of the bulbs to LED or to some inferior type?

[mlew]

No LED bulbs anywhere on the bike.

[DiverRay]

The SF wire diagram does NOT show any diode in the system. The right is taken from the right front, and the Left is taken from the left rear. I would look VERY CLOSELY at the grounds in the pilot box, tack, and front end. It's all I can think of for now.

[mlew]

The SF wire diagram does NOT show any diode in the system. The right is taken from the right front, and the Left is taken from the left rear. I would look VERY CLOSELY at the grounds in the pilot box, tack, and front end. It's all I can think of for now.

Problem is that the 79SF only has one indicator for the turn signals, not a right and left like the 80SG. I cant find a wiring diagram that shows the single indicator and how it is wired. Cant tell if mine is correct without something to compare it to.

[DiverRay]

My factory diagram is VERY VAGUE at the pilot box! I'm getting ready to go to work for the next 4 days, so I will not have a chance to scan it for you. Try catatonic bugs website and see if one of the PDF's he has includes the factory diagram. If not, I'll try and post it Monday afternoon.

[TopCatGr58]

Mark,

The wiring diagram I have from the UK/German site shows the 6 wire plug for the pilot box, but doesn't show EXACTLY which wires go to the BULB, but it shows the left and right brown/green wires of the turn signal circuits going to it, along with a common black ground, grey to the light checker unit, a light tan 12V+ line, the black/red striped wire from the oil pressure sender unit. IIRC, the light checker and the oil sender are both just circuits that connect to GROUND to activate the lights....the 12V+ feeds both the Oil and Headlight bulbs, but the turn signal indicator is powered from the brown/green signal wires!

SO...like Ray and Phil said, there isn't a DIODE in that circuit, it relied on the resistance of the OTHER turn signal circuit to NOT backfeed into the side that isn't being powered by the active turn signal. The MikesXS site has a diode kit for folks that want to add LED lights to prevent the power from backfeeding to the other side since the LEDS need so much less power vs. a 27Watt incandescent bulb.

You say the oil and headlight bulbs flash when the turn signal indicator flashes....They are not supposed to share that common black ground....so I would take the pilot box, remove the bulbs, separate the ground wire and then meter the ground wire thru to the frame to see if it's a good ground vs. a lot of resistance or even open and that the signal indicator is using them backwards as a ground source, and lighting them at the same time!?

T.C.