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Old 12-30-2017, 07:52 PM   #1
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Join Date: Aug 2006
Location: Bellingham, WA
Default Double Checking Headlamp Switch Operation

Hey TB, probably the first of many questions as I resurrect this 92 740, if you guys can give some input on what seems like an odd headlamp switch behavior, it would be extremely helpful so I can stop running around in circles.

Ignition Off:

All the way to the left: system completely off, no headlamps, interior, or parking

Middle position: headlamps on, parking lamps on, interior lamps on

All the way to the right:
system completely off, same as first position

Ignition On:

Left: system completely off

Middle: Everything on

Right: Everything on

From some browsing, it sounds like there were some machines equipped with DRL as factory, but the lamps that are activated in the middle position are not dimmer than usual, and the high beams can still be activated in either position, which apparently shouldn't be possible on DRL equipped cars. Also to have all of the dash lamps on in the DRL position, to me at least, would be strange.

Anyways, these cars are old, maybe a cooked switch or a stuck relay? Or maybe this is normal and the only options for the headlamps are always on, or on only when running?

Thanks gang.
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Old 12-30-2017, 08:24 PM   #2
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lummert's Avatar
Join Date: Jan 2008
Location: Portland IN

I vote for a bad light switch.
Trying to understand stupid people is like trying to pick up a turd by the clean end.
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Old 12-31-2017, 12:53 AM   #3
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Join Date: Feb 2008
Location: Kansas, USA

Originally Posted by sclay View Post
stuck relay?.
On 1987, they show park light feed, from light switch, going to headlight power relay, and then another wire feeds to instrument, interior stuff, then park lights.

Pull headlight relay out, and see which female blades are hot. With ignition switch on,

park lights - two hots
headlight - three hots
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Old 01-01-2018, 02:47 PM   #4
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Join Date: Aug 2006
Location: Bellingham, WA

Mystery solved for anyone following along:

The age old tale told many times before, the curse of the PO.

Someone swapped the Power Window/Seat Heater relay and the Headlamp relay. Silly fix, should have caught it from the get go.

Turns out, relay J doesn't gets a little overly excited being in relay K's spot.

Thanks for the input TB!
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