LenB
September 4th, 2008, 01:43 PM
My truck is 11 years old and I just replaced the stock main head lamp / running lamps switch again, (they appear to last about 5 years). The switch is rather rugged, simple and repairable. But it can (fail) at the most inopportune times. The first time mine failed it was 10 pm - we were out 20 miles from the nearest paved road in the Inyo Mountains boardering death valley - without a functiong switch you have no running lights, instument lights or head lights. Since I wire my aux driving lights on a completely separate circut and switch I was able to safely complete my drive.
The reason they fail is that the plastic base plate that holds the metal contacts within the switch melts and displaces the contacts. The reason the base plate melts is that there is no relay to reduce the load of electrical power passing through the switch.
I consulted the board on how to install a relay -- but got no joy..... so decided to get some external help to make sure I understood how to wire up a relay before I installed my simple and effective relay. Hella make a good relay with a pocket for a standard fuse (clever idea) ($9.) but the headlamp circuts on the rover already have 6 fuses to handle problems. I decided on a bosch 12v 30 amp relay that cost about $12... there are less expensive units ($3 to $4.)
I built a harness and tied it into the segment of the switch that only turns on the head lights - not the running lights and it seems to be working like a champ. I currently have the relay setting outside the dash, just below the instrument cluster so I can monitor any unusual heat that may be generated by the relay. After I am satisfied that it works without issue I will move it inside the dash behind the instrument cluster.
The only modification I made to my factory switch harness was to cut the blue wire (the wire that supplies power to the headlights from the switch) to install 2 bullit connectors. one for going to the relay - the second for comming back from the relay.
The reason they fail is that the plastic base plate that holds the metal contacts within the switch melts and displaces the contacts. The reason the base plate melts is that there is no relay to reduce the load of electrical power passing through the switch.
I consulted the board on how to install a relay -- but got no joy..... so decided to get some external help to make sure I understood how to wire up a relay before I installed my simple and effective relay. Hella make a good relay with a pocket for a standard fuse (clever idea) ($9.) but the headlamp circuts on the rover already have 6 fuses to handle problems. I decided on a bosch 12v 30 amp relay that cost about $12... there are less expensive units ($3 to $4.)
I built a harness and tied it into the segment of the switch that only turns on the head lights - not the running lights and it seems to be working like a champ. I currently have the relay setting outside the dash, just below the instrument cluster so I can monitor any unusual heat that may be generated by the relay. After I am satisfied that it works without issue I will move it inside the dash behind the instrument cluster.
The only modification I made to my factory switch harness was to cut the blue wire (the wire that supplies power to the headlights from the switch) to install 2 bullit connectors. one for going to the relay - the second for comming back from the relay.