Fog lights not working, calling all electricians Options

[malcolm2]

My guess on operation: When turned on and on low beam (OEM design) the relay activates (12v across 86 & 85) coil magnetizes and pulls the arm down to sends 12 volts thru 87.

knob in or high beams on and we have no path from 30 to 87 cause you loose the magnet and the spring opens the circuit and the lights go out.

so the WH/ylw wire comes from 87?

[malcolm2]

One more bump...

No action on electrical issues tonight?


Anyone have ideas on what happened, more to look for, how to fix?

[messix]

corrosion on contacts make a high resistance and cause a high amp load on the circuit melting the relay socket, or some one put in higher wattage bulbs in 35 watt fog light and melted relay socket.

[malcolm2]

corrosion on contacts make a high resistance and cause a high amp load on the circuit melting the relay socket, or some one put in higher wattage bulbs in 35 watt fog light and melted relay socket.

you are referring to contacts within the relay? So the relay could check out, but still be an issue with the heat? I guess I should stick one of the spares in and see what happens.

The bulbs are stock from a 73, I'll have to check, but I am pretty sure they are 35w.

[Mike Bellis]

Most likely cause of the melting was a loose connection at the relay. This causes a micro arc at the terminal heating it up. This is common for this type of relay.

[messix]

corrosion on contacts make a high resistance and cause a high amp load on the circuit melting the relay socket, or some one put in higher wattage bulbs in 35 watt fog light and melted relay socket.

you are referring to contacts within the relay? So the relay could check out, but still be an issue with the heat? I guess I should stick one of the spares in and see what happens.

The bulbs are stock from a 73, I'll have to check, but I am pretty sure they are 35w.

most likely the relay socket will need to be replaced, all the melted gunk will keep from making a good electrical connection

[914Mike]

Check the pins on your relays. If you look closely you will see the they are actually split into 4. I used an Xacto blade to spread them a little before inserting them to insure good contact. It's also possible to squeeze the rings on the socket a little when they get loose.

[malcolm2]

Check the pins on your relays. If you look closely you will see the they are actually split into 4. I used an Xacto blade to spread them a little before inserting them to insure good contact. It's also possible to squeeze the rings on the socket a little when they get loose.

I did try one of the spare relays and the lights came on. (IMG:style_emoticons/default/piratenanner.gif) (IMG:style_emoticons/default/piratenanner.gif) I will go back and see if I can clean out the relay plug a bit to get the melt out and I will spring the pins too.

If I have to go as far as replacing the plug, does anyone have any recommendations on that?

All the separate relay plugs have different color wires, not that that is too much of an issue, but it would be nice to find a plug with the same color wires. I suppose a complete fuse panel purchase might be in order.

Can't remember if the 2 914 in the JY have fuse panels left in them.

Would these be available new?

Thanks for the suggestions,

Clark

[Tom]

So it was a bad/dirty connection? Seem to remember saying check those in post #4.
Glad you finally found it.
As to exactly why you were reading voltage in post #1, but getting no fog light when you connected them: with no ground hooked to the end of the fog light circuit ( the bulb was not in the circuit and the normal path to ground is thru the bulb to ground) this is an open circuit and all points of the + circuit will read battery voltage. When you hooked the bulb into the circuit, that did make a complete circuit to ground, however, the bad connection at the relay was dropping all or most of the voltage across it instead of across the bulb.
Now, why did the relay socket melt. Power dissipation in a very small area that had no way to deal with the heat. It should have been 0 ohms and then there would be no power dissipation across that connection and no heat build up. Why power dissipation? Because the bad connection was not always so bad (high ohms across the connection). When it was a lower ohms connection, say 1 or 2 ohms, it was causing 36 watts at 1 ohm and 18 watts at 2 ohms to dissipate in that small area. As the heat built up, the connection rapidly failed to a much higher resistance due to the heat causing oxidation and plastic/rubber contamination and possible arcing resulting in even more heat.
That's why I said in post #4 Check up stream for all connections, ensure they are clean and tight.
Well, that's my story anyway,
Tom

[malcolm2]

So it was a bad/dirty connection? Seem to remember saying check those in post #4.
Glad you finally found it.
That's why I said in post #4 Check up stream for all connections, ensure they are clean and tight.
Well, that's my story anyway,
Tom

My limited experience with voltage left me not thinking of the relay as a connection. So in my mind, there were no more connections from the harness in the front trunk to the relay. All of those had been checked.

So I planned to eventually drop the fuse panel and check the connections on the switch, still not thinking of the relay as a connection. But I did know the relay was a possible failure point.

Well it obviously is a connection, something that I will look at sooner next time for sure. (IMG:style_emoticons/default/shades.gif)

I'll put my hands on this in an hour or so and see if I can make good tight connections at that lightly melted plug. Fingers are crossed!

UPDATE: cleaned the brittle rubber or plastic from the melt, pinched the "rings" on the socket that connect to the relay and I spread the pins in the relay. Also used some emory cloth and cleaned the pins and the inside of the relay socket rings. Put my light back together and turned it all on. Hit the high beams 10 or 12 times and everything is working fine.

Thanks again.