Headlights won't work. NOT A BLOWN FUSE!

Mazda_Power · Post by **Mazda_Power** » November 21st, 2005, 12:22 am

OK, I can't drive at night. This is getting rediculous! I can't hear a relay turn on, anyone know where the headlight relay is? Anyone else have this problem?

Grants · Post by **Grants** » November 21st, 2005, 1:19 am

The headlight relay is under the dash above your feet.

94 model? The diagram is here:
http://www.mx3er.com/info/1994%20Wiring%20diagrams.pdf

Page 30.

The wire colours going to it should be:
- RED / BLUE (switched ground for controls)
- RED (constant 12V)
- WHITE / RED (switched 12V)

if you can't hear the relay operating, check the RED wire for 12V. If thats ok, bridge a ground wire to the RED / BLUE wire and the relay should work. If it doesn't - time for a new relay.

Mazda_Power · Post by **Mazda_Power** » November 21st, 2005, 10:12 am

OK, I'll give that a shot. We'll see what happens tonight. Thanks Grants.

Mazda_Power · Post by **Mazda_Power** » November 22nd, 2005, 1:13 am

Grants wrote:The headlight relay is under the dash above your feet.

94 model? The diagram is here:
http://www.mx3er.com/info/1994%20Wiring%20diagrams.pdf

Page 30.

The wire colours going to it should be:
- RED / BLUE (switched ground for controls)
- RED (constant 12V)
- WHITE / RED (switched 12V)

if you can't hear the relay operating, check the RED wire for 12V. If thats ok, bridge a ground wire to the RED / BLUE wire and the relay should work. If it doesn't - time for a new relay.

So if I create the ground (and the red wire has 12V+) the lights should turn on (as the switch should become "live"). If not the relay might be stuck closed?

Thanks

Grants · Post by **Grants** » November 22nd, 2005, 1:58 am

Just grab a piece of wire and short it from ground to the RED / BLUE wire. That will bypass the switch. If you have 12V on the RED wire (it supplies both the contact and one side of the coil) and short the RED / BLUE wire to ground, the relay should operate if its ok. If the relay doesn't operate, the coil in it is probably burnt out so it can't close the contact between the RED wire and the WHITE / RED and make the lights come on.
(If the relay was stuck "closed" the lights would be on all the time.)

If the relay operates and the lights come on, the fault is probably in the switch.

If its shown to be the relay you might be able to "borrow" one from the air con or something to prove it (on the firewall).

Hope that makes sense.

Mazda_Power · Post by **Mazda_Power** » November 23rd, 2005, 3:00 am

OK. I printed out your original info and put it to the test. When the blue/red wire is grounded nothing happens. Did you mean to back probe the connector while the relay is still on. Now that I think about it, of course you did. Hmmm.... Also another interesting thing, the fuse for the headlights does get 12V.

Grants · Post by **Grants** » November 23rd, 2005, 3:49 am

Yes - you need to keep the relay connected to all the wires when you short the ground out. All we're doing here is testing if the actual relay is ok by puting 12V and ground across the coil. If it doesn't operate it must be u/s.

The fuse for the headlights is before the relay so if you have 12V at the relay you must have 12V at the fuse.

Mazda_Power · Post by **Mazda_Power** » November 23rd, 2005, 10:35 am

Thanks again Grants (I was up till 2 last night working on it, check my post time! [*edit there is no post time]) I'll try that red / blue wire.

Aaron

Mazda_Power · Post by **Mazda_Power** » November 24th, 2005, 1:25 am

Tried it... no luck.

Grants · Post by **Grants** » November 24th, 2005, 2:18 am

Sounds like the relay must be bad..

If its shown to be the relay you might be able to "borrow" one from the air con or something to prove it (on the firewall).

Should just unplug and hopefully the headlight one is the same

Mazda_Power · Post by **Mazda_Power** » November 26th, 2005, 7:08 pm

Grants wrote:Sounds like the relay must be bad..

If its shown to be the relay you might be able to "borrow" one from the air con or something to prove it (on the firewall).

Should just unplug and hopefully the headlight one is the same

There is a relay it fits into, I tried it. No luck.

I'll try some other options tonight.

Grants · Post by **Grants** » November 26th, 2005, 8:13 pm

Whith the headlight switch on, check for a voltage across the RED and RED / BLUE wires. You should have 12V if the control circuit is ok.

Mazda_Power · Post by **Mazda_Power** » November 27th, 2005, 6:59 pm

Thanks again Grants, I tried both air conditioning relays (they were the same). I'll check for continuity tonight.

Mazda_Power · Post by **Mazda_Power** » November 27th, 2005, 8:46 pm

Just a quick note. I took a 12V charge and put it to WHT/RED wire and I have temporary lights!!!

Grants · Post by **Grants** » November 27th, 2005, 11:59 pm

Mazda_Power wrote:Just a quick note. I took a 12V charge and put it to WHT/RED wire and I have temporary lights!!!

You should be able to do that by shorting the RED wire at the relay to the WHITE / RED. All the relay does is close a contact across those 2 wires. You've checked previously that the RED wire has 12V - is this where you connected the picked up the 12V for the WHITE / RED wire?