Would A Bad Headlamp Relay Do This?

[soldenka]

Sons 1989 Camry - battery died yesterday. Had it checked by two shops - OK. It was drained to about 25% so I charged it overnight and put it back in this AM. Started right up. Alternator was charging at 14.3V. This evening battery died again. Jumped it and drove it home. Turned it off and tried to immediately restart it - nothing at all. Noticed a loud clicking sound coming from the fuse box next to the battery. It was the headlamp relay. Removed the relay and the clicking stopped. Removed the battery to recharge it - it was fully charged...? So, put the battery back in the vehicle (sans the headlamp relay) and the car started right up. No headlights, of course. Could a bad relay either drain a battery or cause no power to get to the ignition?

[88 LE]

Originally Posted by soldenka

Could a bad relay either drain a battery or cause no power to get to the ignition?

A bad headlight relay that stays energized can cause the headlights to stay on and drain the battery. Ignition is on a different circuit.



Have you checked the relay to see if it is bad? The contacts on the relay are NO (normally open) when the coil within the relay is not energized.


The relay has constant power supplied to it (battery --> 40A main fuse --> relay). Ground is supplied by the headlight switch. So if the relay is clicking, its getting an intermittant ground from somewhere that it shouldn't. Or its getting ground from somewhere and intermittant power.

[soldenka]

88LE - thanks for the response. Still trying to collect all the "facts" on this one as it is my sons car and each event has occured while he has been driving.

If I understand correctly - the relay could be properly powered, but improperly grounded OR properly grounded and improperly powered. Is there a way to tell which it is? Where excatly is the ground for the relay?

How would one test a relay?

When the car is turned off/parked after driving the lights do in fact go off automatically as they should. However the battery drains. If you physically turn the lights off at the stalk, no drain on the battery.

If a loose ground or power supply would one not expect to see the lights "flickering" while driving? They saty on strong...

[Sturdavj]

The best way to test a relay is with a multi meter & a wiring schematic that shows the relay configuration, as well the head light electrical circuit.

If this happening while its being driven, and you suspect it is the headlight relay preventing starting you may want to have your son attempt to start the car while you jiggle the relay, you may want to even tap on it with a screw dirver handle.

I would hesitate to remove it while it's under a load, but you may want to check it a dark garage to see if it draws an arc when you pull it off it's socket.

Let us know what you find out

[88 LE]

Originally Posted by soldenka

Where excatly is the ground for the relay?

The ground point is at J/B No. 1 (junction block #1). Its either behind the drivers side dash or kick panel (the picture in my electrical wiring diagram manual is not really clear on the location).

How would one test a relay?

With a power source (battery or power supply) and a DMM.

1. Check resistance across the contacts of the relay with the relay not energized. The reading should be O.L indicating infinite resistance or an open.

2. Check resistance across the contacts of the relay with the relay energized (power and ground applied to the coil of the relay). You should get a reading of 0 ohms or close to it.

3. You can also check the resistance across the coil of the relay, with no power and ground to the relay.


Before you do this, you need to know the pinout of the relay. Some relays are labeled and some are not.

When the car is turned off/parked after driving the lights do in fact go off automatically as they should. However the battery drains. If you physically turn the lights off at the stalk, no drain on the battery.

Hmm... thats weird. Maybe theres something going on with the light auto turn off.

Looking at the schematic for the light auto turn off, I see a integration relay, but I haven't quite figured out how it works.

I just know that it somehow turns off the headlights when the headlights are on, ignition off, and the drivers door is opened.