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EFV-8 Club Forum / 1940 Ford Discussion / Circuit Braker:

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Posted By Discussion Topic: Circuit Braker: -- page: 1 2     fortyford 08-13-2020 @ 9:04 AM reply profile send p.m. Member Posts: 206 Joined: Nov 2009 Is there a way to test the circuit breaker?As probably y'all have read my posting on the Ford Barn about my dim headlight problem.For reasons I have narrowed it down to the breaker I THINK.I have 6 volts on both post with nothing on and when I turn lights on I have 6 volts on one post and 4.74 on the other post.I this normal?Sorry about my topic spelled wrong! This message was edited by fortyford on 8-14-20 @ 5:44 AM trjford8 08-13-2020 @ 2:15 PM reply profile send p.m. Senior Posts: 4202 Joined: Oct 2009 If you have 6 volts at each end with nothing on and then 4.74 when the headlights turned on I think you have a problem other than the circuit breaker. Just to be clear we are talking about the small metal box that has a series of holes in it that's mounted on the firewall above the steering column. Make sure all the connections to the breaker and to the lights are clean and make good contact. Tug on the wires and make sure the end connectors are securing the wires. If you have any broken insulation on the wires look at the wiring and see if you see corrosion. The old copper wire should look just like copper and not appear to be black. If black appearing you have a lot of resistance in the system which results in low voltage and warm to hot wires. Resistance equals heat. fortyford 08-14-2020 @ 5:42 AM reply profile send p.m. Member Posts: 206 Joined: Nov 2009 Can the breaker be removed and cleaned or serviced or does it have to be replaced? TomO 08-14-2020 @ 7:24 AM reply profile send p.m. Senior Posts: 7243 Joined: Oct 2009 To be sure, do a voltage drop test, connect the COM lead of your meter to the NEG battery post and the + lead to the output of the circuit breaker and turn on the lights. Normally the volt meter will read 0.1 volts or less. If it reads more, like the 1.24 volts that you posted, move the + lead to the input side and read the meter, it should read less than 01.V. If it does the circuit breaker is bad. The method of voltage reading that you are useing does not take into consideration of all of the circuit resistance, like a voltage drop test does. I have never tried to take apart the circuit breaker to see if I could clean the contacts, as it has never been a problem on my car. Tom fortyford 08-14-2020 @ 7:43 AM reply profile send p.m. Member Posts: 206 Joined: Nov 2009 Tom,I am using a digital meter.Does this matter?I guess I will have to make up a long lead wire to do this.Long way from battery to breaker,if I am understanding this correctly? This message was edited by fortyford on 8-14-20 @ 7:51 AM TomO 08-14-2020 @ 8:23 AM reply profile send p.m. Senior Posts: 7243 Joined: Oct 2009 A digital meter is the best way to do this measurement. I have an older meter and the leads are 4ft long, so I can rest the meter on the glove box door and still reach the battery and the circuit breaker. Tom fortyford 08-14-2020 @ 1:13 PM reply profile send p.m. Member Posts: 206 Joined: Nov 2009 Tom,with lights on I have 1.20 on one side and .05 on other post. TomO 08-15-2020 @ 7:17 AM reply profile send p.m. Senior Posts: 7243 Joined: Oct 2009 It looks like your circuit breaker is bad. The .05 is a good reading. The 1.15 drop across the circuit breaker is excessive. I will look at my spare circuit breaker to see if there is an easy way to repair one and let you know what I think. Tom 40 Coupe 08-15-2020 @ 9:43 AM reply profile send p.m. Senior Posts: 1645 Joined: Oct 2009 With the dim lights on place a jumper across the two terminals of the circuit breaker. If the lights get bright, you may have a problem with dirty contacts. If the lights stay dim, look for your problem somewhere else. TomO 08-17-2020 @ 6:51 AM reply profile send p.m. Senior Posts: 7243 Joined: Oct 2009 I looked at my spare circuit breaker and it looks like you can drill the rivets that hold the cover on, clean the contacts and reinstall the cover with small screws. Before you do that, I noticed that the terminal posts have 2 nuts each and like the ignition resister, the bottom nuts can come loose when the upper nuts are removed, so I would remove the wires, loosen the lower nuts 1/2 turn and tighten them, replace the wires and tigh6ten the top nuts. Use a wrench with a short length as the nuts only need about 10in.lbs. to be tight. Tom

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