Passenger side dip beam out.

[blade7]

Fuse is ok, bulb looks OK too. How do I check this connector with my multi tester for dip beam power?

944 2.jpg (2.93 MiB) Viewed 57 times

[dr bob]

The DIN wiring insulation colors for the headlights have High (Main) Beam power on WS (white), Low (Dipped) Beam power on GE (yellow), and all chassis ground connections are BR (Brown).

With the headlights on and low/dipped beam, you should see battery voltage at the YELLOW wire contact in the socket, referenced to chassis ground.

Assuming you are using a conventional (Not LED) headlight bulb, you can use your Ohm meter to check for filament continuity between the bulb contacts that correspond to the YELLOW and BROWN wires. The reading should be in the <6 Ohms range if the filament is intact, and show infinite if the filament has failed/burned out.

I don't have the 944/951 wiring diagrams handy, so don't know the specific fuse arrangements. My car (1989 928) has individual fuses for each bulb filament, so a separate fuse dedicated to the right dipped beam filament. If yours has similar, of course you'll want to be sure you are inspecting the correct fuse. Bottom line for me anyway is that I can't rely on the opposite headlight working on low/dipped beam as an indicator that the fuse for the right side is intact.

If the main (high) beam element is working, it's likely the brown ground connection to chassis is intact.

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All that said, most "bulb doesn't work" conditions are caused by simple filament burn-out. Fuses are installed to protect wiring from overload and melted insulation, so i don't expect that protection to kick in unless there's a wiring fault to ground. The cars use relays to manage the various lighting functions, and one can pretty safely assume that if the opposite-side low-beam works, the headlight relay is also functioning.

For me, bulbs get replaced in pairs. Knowing the tiny bit I do about mass-product manufacturing and consistency, I figure that when one bulb decides to fail in normal use, the other similar bulbs are not far behind. And because brightness and color and lens condition vary with time and duty, I want the two bulbs to look and illuminate the same. I used to save the remaining-good bulb as a spare, but have revised that policy to just keeping new bulbs as spare, at least for the various markers and rear signal bulbs. The factory US headlight bulb size makes carrying them in the car as ride-along spares a bit of a chore.

Hope this helps!

[blade7]

Hi, I am using conventional bulbs, and there are fuses for each filament. Excuse my ignorance, but what should I set my multimeter to, when checking the yellow/brown contacts.

[chrischrischris]

You want Volts DC (not AC since that's what you would use in your house).

[blade7]

Oddly there was power down the yellow lead, and continuity on the bulb. Perhaps the bulb is playing up when it gets power. Think I'll try a new bulb next.

[blade7]

Fitted a new bulb, it worked for a few seconds and then nothing, there was 10.8v on the yellow lead. Followed the bulb loom back into the engine bay to the connector, and twisted it back and forwards. The dipped beam is working now. So do I cut out that connector and make a permanent connection there? Or leave it as it is?

[dr bob]

When I see wonky issues like the one you describe, my next step might be a voltage check between Yellow and Brown with the bulb connected. Poke your meter probes into the back of the connector terminals if you can for this, or leave the connector a little off of fully-seated on the bulb. When there's a partial wire break or a corroded connection, the resistance from that will cause voltage to drop at the bulb connections. The meter alone doesn't draw enough current to cause that effect, but with the bulb in the circuit you can see it with the DC voltmeter in parallel.

The headlight wiring twists and flexes in normal operation of the headlights, making that wiring a prime suspect in any voltage drop concerns. the other prime suspect is the ground connection to the body for the brown wire. If you see a voltage drop at the bulb terminals, swap your meter lead from the brown wire terminal to a solid chassis ground point, and measure from the yellow terminal at the bulb. If you now see battery voltage, the resistance is in the brown wire ground point or the brown wire itself.



My car gets an annual (give or take) electrical maintenance clinic that includes inspecting and cleaning the various ground points and connections, plus the battery-to-chassis and engine-to-chassis cables. Some clinic cars with odd electrical issues have been magically 'cured' with this attention, enough so that I do it as PM now on my own and recommend it to others. A 10mm socket, a brass 'detailers' toothbrush, and a bit of Vaseline to seal/coat the treated connections is all that's usually needed. And an hour or so, the diagrams of ground point locations, and a battery terminal cleaning brush. I also do some battery testing for specific gravity, and a voltmeter test of the battery itself and the charging voltage it sees from the alternator.

[blade7]

The car had been in dry storage for over 10 years until recently, so some issues aren't unexpected. The battery was new when it was laid up, and its been on a trickle charger ever since.

[danmartinic]

My understanding is that the 944--or at least my '88 951--does not have headlight relays?

Anyway... I found a wire with rubbed-through insulation kept blowing one side's fuse. Apprently common right at the housing bracket

FYI the Toyota halogen dealer-supplied light kit (lens & bulbs with optional-to-install relays--meant for 1980s Land Cruisers and such) is an excellent and super cheap replacement for our sealed-beam lights

You might have to provide a VIN; I just pulled one from the web. Note they are Euro lenses

[blade7]

Not sealed beam on the UK headlamps.