MKIII Headlight Problem

Supra275 · 08-26-2008, 10:00 PM

Newbie to the forum. I have a 1989 MKIII 3 litre Turbo Supra with what appears to be an unusual fault with the headlights. With the main light control in the OFF position, the engine running, headlight selection to low beam and the transmission in D the headlights intermittently light ( they do not pop up ). When driven forward the lights flicker and when stationary will remain ON until the transmission is disengaged from D ( this flickering eventually burns out the headlight relay). Immediately reengaging D will not bring the headlights on until the car moves forward. Sometimes the headlights remain on when the vehicle is parked ( key removed from ignition ). As far as I can tell it is not any of the following: faulty headlight relay, faulty / lose wiring associated with the lighting control switch, faulty relay / fuse box wiring. I am beginning to suspect a faulty retract control relay. Has anyone experience a fault like this or have some other suggestions as to what the fault could be. Thanks.

I have a few more details about the fault.

I removed the headlight relay and connected a LED indicator in its place which allowed me to see what was occurring across the relay coil.

With the engine running vehicle stationary and in either P,R,N,D,P2 or L with the main light control switch OFF and either HIGH or LOW beam selected the headlight relay is OFF.

Select either R, D, P2 or L whilst remaining stationary the headlight relay is OFF

Drive the car in either of the above and the relay goes on and off at a rate that is dependent on the speed of the vehicle ( only tried this up to 5 mph ). Interestingly if you stop when the relay is ON it will remain ON until either N or P is selected. Reselecting any of the other positions after this will not switch the relay on until the car is moved and starts to go on and off again.

Another little quirk to this problem is that with the ignition ON, engine not running and the main lights switch OFF selecting HIGH beam switches on the main beam headlights and the blue main beam indicator on the dashboard. This does not happen when dipped is selected.

In all of the above the headlights remain in the retracted position. Also the O/D light flashes when the O/D is selected – I believe this to be a gearbox setup problem and is not associated with this one.

Thanks.

suprabahamut · 09-05-2008, 02:29 AM

It sounds like a wiring problem but I have a manual transmission. Wait for a wiring guru to write. Check the fuse box with a DVOM check at the relays, and the different places at the fuses. Check both volts and ohms it might tell if there is a lot of resistance. Also check by wiggling the different wires at the lights it might show a open some where. I know there has to be someone here that can diagnose this problem. See if Mrnickeye writes he is a geniuses with the supra's.

Supra275 · 09-05-2008, 03:06 PM

Thanks for the reply.

I have wiggled and waggled every wire that I can access and it does not affect the lights. I have also checked some of the wiring for shorts etc but found nothing so far ( the wiring diagram is not ideal as it is for USA / CANADA ). The fault exhibits its self in a very consistent way – the only aspect of the fault that is unpredictable is the headlights remaining on when the main light switch is OFF and the key removed from the ignition. Sometimes, after being parked overnight, when the car is started the headlights come on but do not pop up and when the car is driven forward they flash at a rate proportional to the speed of the vehicle, as described before.

mnewxv · 09-05-2008, 07:39 PM

hows the stereo? when the lights flash are they dim? good charge on batt? maybe alternator?

Supra275 · 09-05-2008, 09:06 PM

The battery charges ok - when the engine is running the battery terminal voltage is approximately 14.1V at 2000 rpm with the headlights / lights, rear heated window, heater blower and fog lights ON. The battery holds charge ok for over at least a week. When the lights flash they are at full intensity as it is the headlight relay coil which is being switched – checked by using a LED / resistor across coil socket in the fuse / relay box.

Interesting – the stereo ( not original factory fit ) will not operated at higher volumes – its LED display flickers with the music and sometimes the radio cuts out and restarts as if it were switched OFF and back ON again. I assumed it was a high resistance contact somewhere in the supply cable or fuse and would fix it at a later date.

08-26-2008, 10:00 PM	#1
Supra275 Stock Join Date: Aug 2008 Location: England Posts: 4	MKIII Headlight Problem Newbie to the forum. I have a 1989 MKIII 3 litre Turbo Supra with what appears to be an unusual fault with the headlights. With the main light control in the OFF position, the engine running, headlight selection to low beam and the transmission in D the headlights intermittently light ( they do not pop up ). When driven forward the lights flicker and when stationary will remain ON until the transmission is disengaged from D ( this flickering eventually burns out the headlight relay). Immediately reengaging D will not bring the headlights on until the car moves forward. Sometimes the headlights remain on when the vehicle is parked ( key removed from ignition ). As far as I can tell it is not any of the following: faulty headlight relay, faulty / lose wiring associated with the lighting control switch, faulty relay / fuse box wiring. I am beginning to suspect a faulty retract control relay. Has anyone experience a fault like this or have some other suggestions as to what the fault could be. Thanks. I have a few more details about the fault. I removed the headlight relay and connected a LED indicator in its place which allowed me to see what was occurring across the relay coil. With the engine running vehicle stationary and in either P,R,N,D,P2 or L with the main light control switch OFF and either HIGH or LOW beam selected the headlight relay is OFF. Select either R, D, P2 or L whilst remaining stationary the headlight relay is OFF Drive the car in either of the above and the relay goes on and off at a rate that is dependent on the speed of the vehicle ( only tried this up to 5 mph ). Interestingly if you stop when the relay is ON it will remain ON until either N or P is selected. Reselecting any of the other positions after this will not switch the relay on until the car is moved and starts to go on and off again. Another little quirk to this problem is that with the ignition ON, engine not running and the main lights switch OFF selecting HIGH beam switches on the main beam headlights and the blue main beam indicator on the dashboard. This does not happen when dipped is selected. In all of the above the headlights remain in the retracted position. Also the O/D light flashes when the O/D is selected – I believe this to be a gearbox setup problem and is not associated with this one. Thanks. Last edited by Supra275; 08-28-2008 at 10:08 AM. Reason: Additional information regarding the fault

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09-05-2008, 02:29 AM	#2
suprabahamut 3" Exhaust Join Date: May 2007 Location: greensboro Posts: 242	It sounds like a wiring problem but I have a manual transmission. Wait for a wiring guru to write. Check the fuse box with a DVOM check at the relays, and the different places at the fuses. Check both volts and ohms it might tell if there is a lot of resistance. Also check by wiggling the different wires at the lights it might show a open some where. I know there has to be someone here that can diagnose this problem. See if Mrnickeye writes he is a geniuses with the supra's.

09-05-2008, 03:06 PM	#3
Supra275 Stock Join Date: Aug 2008 Location: England Posts: 4	Thanks for the reply. I have wiggled and waggled every wire that I can access and it does not affect the lights. I have also checked some of the wiring for shorts etc but found nothing so far ( the wiring diagram is not ideal as it is for USA / CANADA ). The fault exhibits its self in a very consistent way – the only aspect of the fault that is unpredictable is the headlights remaining on when the main light switch is OFF and the key removed from the ignition. Sometimes, after being parked overnight, when the car is started the headlights come on but do not pop up and when the car is driven forward they flash at a rate proportional to the speed of the vehicle, as described before.

09-05-2008, 07:39 PM	#4
mnewxv 3" Exhaust Join Date: Aug 2008 Location: melrose, ma Posts: 108	hows the stereo? when the lights flash are they dim? good charge on batt? maybe alternator?

09-05-2008, 09:06 PM	#5
Supra275 Stock Join Date: Aug 2008 Location: England Posts: 4	The battery charges ok - when the engine is running the battery terminal voltage is approximately 14.1V at 2000 rpm with the headlights / lights, rear heated window, heater blower and fog lights ON. The battery holds charge ok for over at least a week. When the lights flash they are at full intensity as it is the headlight relay coil which is being switched – checked by using a LED / resistor across coil socket in the fuse / relay box. Interesting – the stereo ( not original factory fit ) will not operated at higher volumes – its LED display flickers with the music and sometimes the radio cuts out and restarts as if it were switched OFF and back ON again. I assumed it was a high resistance contact somewhere in the supply cable or fuse and would fix it at a later date.