Low beams not working but high beams are

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ccmt
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Joined: Mon Aug 03, 2015 4:14 pm
My tercel:: '86 4WD SR5
Location: Washington, D.C.

Low beams not working but high beams are

Post by ccmt »

Hi Folks,
I was hoping y'all could help me with a lighting mystery. I recently swapped out the wiper/headlight assembly on my '86 for the Intermittent Wiper assembly (viewtopic.php?f=7&t=5623). Unfortunately, since doing that only my high beams seem to work. When the switch is set to low beams the blue high beams indicator on the instrument panel is like half illuminated but the headlights are dark. Then when I flip to high beams the indicator gets brighter and the high beams come on.

Here's the weird thing though. When I unplug the intermittent wiper and assembly and plug the original assembly back in the problem persists! So now, no matter what assembly I use, no low beams! I'm thinking I may have jostled something further up the wiring but I'm not even sure which of the mess of wires to follow

Anyone have thoughts?

Thanks,
Calen
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dlb
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My tercel:: '87 sr5, '83 dlx parts car
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Re: Low beams not working but high beams are

Post by dlb »

Have you checked the fuses for the headlights? I believe they are under the hood in the fuse box, and there are separate fuses for low and high beams.

Do you have any spare new headlight bulbs you could throw in? I know it's extremely unlikely that burnt out bulbs are the problem but I've learned to rule out the easiest things first.
ccmt
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My tercel:: '86 4WD SR5
Location: Washington, D.C.

Re: Low beams not working but high beams are

Post by ccmt »

Thanks! I checked the fuses and they all look good. I’m thinking it may be the headlight control relay. I tried to check that per the service manual and it seems a bit funky. You’re right, I know I should probably check the bulbs first. I’ll ty that tomorrow. Meanwhile relay is on order at my local dealership (apparently it’s not a discontinued part yet!).
Angel
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My tercel:: 1985 Tercel 5dr 4wd automatic

Re: Low beams not working but high beams are

Post by Angel »

Sometimes the polarity being reversed will do this. Swap the positive and negative around.
ccmt
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My tercel:: '86 4WD SR5
Location: Washington, D.C.

Re: Low beams not working but high beams are

Post by ccmt »

Hmmmm. Not bulb or relay. Any other thoughts?
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ALiveSR5
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My tercel:: Was a stock 1985, SR5, 4WD, 6-speed manual, Wagon.
Location: Pennsylvania USA

Re: Low beams not working but high beams are

Post by ALiveSR5 »

ccmt wrote: Sat Nov 07, 2020 3:32 pm Hmmmm. Not bulb or relay. Any other thoughts?
Well, as my electronics instructor used to say, "Electrons always obey their laws." Of course, he did not tackle Japanese car wiring. :?

Anyway, the pictured control is from a 1985 SR5 - is this what you tried to install or did you remove the one with INT and try one with a variable wiper control? I am not familiar with the 1986 control, if it is different, so I am trying to clarify what you swapped for what.
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Wiper_Turn_Controls.jpg
~
That the blue high beam light glows a bit, when the switch in on Low Beam, could indicate an open circuit, causing a small bit of voltage to leak through a resistant circuit, like a lamp filament or relay coil, or something. It could also indicate a bad ground, causing voltage to pass through the blue light to find ground (Japanese wiring used to be infamous for controlling grounds, instead of the hot).

Make sure, too, that both switches are switching, like they are supposed to - they should both activate the same relays (the connector contacts should be identical). A sticking relay (burnt contacts) or a fried relay coil would cause the circuits to behave differently.

You should be able to test continuity and/or voltage from the control connector to the relay(s) connector(s) and the same from the relay(s) connector(s) to the headlamps. You may have done that already (I could not know) but it could help you isolate where the problem is. Of course the wiring diagrams for both your vehicle and the one from which the "new" control came from may help you trace the circuits.

As I understand, each of the head light and wiper switches can be removed separately. So, you may be able to put your "old" head light switch onto the "new" wiper control. That way, after you figure out the problem, you will be using the original head lamp switch and hopefully not have any more head light problems.

Except for tracing the circuits, by following the electron flow, I do not know what specifics to suggest, since I am not there to do testing. I do not necessarily do orthodox testing on my own stuff :roll: like using jumpers and live voltage to bypass switches and relays to find out what works.
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No other vehicle that I have ever owned had a heart and soul like my 1985 Tercel SR5 4WD Wagon. :D
~
Great minds may think alike but it is the doers who see their visions become reality. :?
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dlb
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Re: Low beams not working but high beams are

Post by dlb »

All I can think of is that some of the headlight wires on the vehicle-side plug have become crossed. I would double check the wires there and make sure they all appear to be going to the right spots. Maybe take a look and make sure there is no corrosion or anything else in the plug. I have had some plugs melt around certain wires and malfunction after that.
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Petros
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Re: Low beams not working but high beams are

Post by Petros »

we were on a cross country road trip once in our Mazada minivan and had the low beams go out. all I had was high beams and since we had much night driving I just adjusted the highs down to a lower position so we could continue until I got it home to check it out.

turns out both the low beam elements were burnt out, it just needed now bulbs. apparently I did not notice one was out when we left, and on the trip the other went out. only the high beam filament worked.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
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