1994 cutlass supreme. the headlamps dont work but the brights do. the headlamp fuse is fine so it might be the relay. how do i tell if the headlamp relay is bad and were is it?

Bright lights wont shut off ? Assume you mean high beams ? Reading how they work might thing high beam relay has stuck contacts inside .

Headlamps
The headlamps may be turned ON 2 different ways. First, when the driver places the headlamp switch in the HEADLAMP position, for normal operation. Second, with the headlamp switch placed in the AUTO position, for automatic lamp control (ALC). During ALC, the headlamps will be OFF in daylight conditions, or low beam operation in low light conditions. Battery positive voltage is supplied to the low beam relay and the high beam relay in the underhood fuse block. When low beam headlamps are requested, the body control module (BCM) supplies ground to the coil side of the low beam relay. This activates the relay and the relay supplies voltage to the left hand low beam headlamp through the LH LOW BEAM fuse and to the right hand low beam headlamp through the RH LOW BEAM fuse. Ground for the left hand low beam headlamp is provided at G101. Ground for the right hand low beam headlamp is provided at G102. When high beam headlamps are requested, the body control module (BCM) supplies ground to the coil side of the high beam relay. This activates the relay and the relay supplies voltage to the left hand high beam headlamp through the LH HIGH BEAM fuse and to the right hand high beam headlamp through the RH HIGH BEAM fuse. Ground for the left hand high beam headlamp is provided at G101. Ground for the right hand high beam headlamp is provided at G102.

Hello. It seems your Toyota's headlamp relays are defective/malfunctioning. Your Toyota has a relay/fuse for the left headlamp and one for the right headlamp. Good luck and keep me informed; if you want to.

There is no relay for the headlamps ,high or low beams . Probably the headlamp dimmer switch is no good , or you have a wiring problem ! Test the electrical circuit with a DVOM - digital volt ohm meter is the way to a proper fix. Looking at a wiring diagram so you know which wires to check an doing voltage drop testing . Free wiring diagrams here http://www.bbbind.com/free_tsb.html Enter the vehicle info. year , make , model an engine size . Under system click on lighting ,then under subsystem click on headlamps . Click the search button ,then the blue link . Now watch these videos .
Basic Electricity for Service Techs Ohm law Current Flow Opens Shorts

How to Use Multimeter to Troubleshoot Common Problems

Electric Testing Techniques You Need to Know

Is it high beam or low beams that are on? Do you have drl? Can't rule out problem with drl module? The headlamp switch has an internal circuit breaker, no relay. The diagram is part of headlamps/drl.

Check fuses, then headlamp switch.

Power comes from headlamp / dimmer switch . Go here for free wiring diagrams http://bbbind.com/free_tsb.html Enter vehicle info year ,make , model ,engine size ! Under system click on lighting then under subsystem click interior light dimming .

From your description, T/S not working with headlamps on, it seems apparent that your turn signals have lost their ground and are grounding back through the headlamps when they are not on.

IF THE HEAD LAMP BULB IS NOT BLOWN THE HEADLAMP FUSE OR RELAY MAY BE BAD.

Your headlamps work off of one fuse. The high and low work on the same fuse so if you don't have low beams then you probably have 2 blown bulbs. The bulbs are a sealed unit and are replaced from the back side of the headlamp itself. Usually with the halogen bulbs if one goes out the other will go out not soon after. Remember when you replace the bulb that you can't touch the bulb itself with your hand because the oil from your skin will give the bulb a short life. Most good Auto parts stores today will assist you in changing the bulbs if purchased from them. Good luck and I hope this hepled.

That should be it for fuse compartments..

If its not the fuse(s) or relay it might bethe switch,, or the motor..

Try to determine if there is power getting to the switch,, if so see if there is power to the motor..

You can find replacement parts pretty cheep on-line..

Hope this helps !!
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