Topic: 65' fog lamp circuit breaker fault

[Hipo giddyup]

 I have installed a 65' fog lamp kit from Virginia Mustang and while the quality is very good, I am on my second circuit breaker in a year. I followed the instructions to the "T" and I am puzzled as to why this breaker doesn't seem to be holding up. The other evening I was out driving and put the fog lamps on. After about 5 minutes I heard the "click" and saw no lights on the vehicle in front of me (they had tripped and turned off). I left the switch on and after a minute I heard the click again and noticed they had turned back on (must have been after the circuit cooled down). This happened last summer into fall and after replacing that switch with another repro, I had no issues up until early November when I retired the car for the winter hibernation. Is this just an issue in a poor quality repro circuit breaker or do I have another gremlin??? Thanks for any input...

[midlife]

It's a 10 amp circuit breaker by design, and the measured current draw on my 66 GT was about 5 amps, yielding a good safety factor of 2.0 for electrical fusing.

If your circuit breaker is tripping, I would immediately suspect a bad ground somewhere in your fog lamp system (including the rear running lights).  A second area of concern would be a suspect switch itself. 

[Hipo giddyup]

 Thanks Midlife, I was hoping you would chime in  . EVERYTHING is new, fog lamp kit, all wiring including the engine rear harness, etc.., attaching hardware,etc. so I will go back through some of the grounds and make sure they still look good. Dumb question as i am not so good with electrical stuff, is there a measurement that can be taken at the ground to make sure it is good?? Resistance,?? And, is there anyway to check the switch itself? Should the switch have a good ground as well?? I have fog lamps on my 67' coupe, followed the wiring details exactly when installing, and I have never had issues over the last 16 years since they were installed. 

[67gtasanjose]

It's a 10 amp circuit breaker by design, and the measured current draw on my 66 GT was about 5 amps, yielding a good safety factor of 2.0 for electrical fusing.

If your circuit breaker is tripping, I would immediately suspect a bad ground somewhere in your fog lamp system (including the rear running lights).  A second area of concern would be a suspect switch itself.

The bad connection (if there is one) will most likely be where things are "getting hot".

It is just as likely an "Offshore" circuit breaker which is manufactured "cheaply"could be your cause of trouble. Also, make sure all of your "contact" (or "star") washers are all in place too. Poor contacts at the circuit breaker will cause it to overheat. I'm not sure what you might be re-doing wrong each time (or even if you are) but if you keep doing the same thing, the same way...you might just end up with the same level of insanity as many electricians have  .

In another thread (not sure who was having the same problem, possibly you?) a few months ago, it was suggested to use a "plastic separator" by another member UNDER the eye loops of the contact...I believe at that time, it may have been noted or suggested that this is "As the factory does". Possibly,  the factory DID use those separators on certain applications but I am not so sure they did so on your 65 Mustang. If a separator is used, it could add to poor conductivity.

Personally, If there is any sign of heat at the breaker posts (studs) when you get them down to look, I would start there. I would install another new breaker from a DIFFERENT source and with the "bare-naked breaker", first slip a star washer onto the studs, then the eye-connector, followed by a brand-new nut and assure yourself it is torqued down correctly. A quality circuit breaker should practically NEVER fail so my "guess" would be something like this is where your trouble is (agree with Randy, if the grounds are all good)

[Hipo giddyup]

  Thanks for the feedback, I will start troubleshooting and checking and let you know what i find or what possibly fixes it. Again, when I replaced the circuit breaker last fall I didn't have any issues driving it since then, until now. Maybe something has worked loose, or possibly two weak or bad breakers  that went south like you say.. I will be heading up to the Ford nationals in Carlisle this week so I will keep my eyes open for an NOS breaker (if i am really lucky to find one).

[Brian Conway]

I have no answers for your dilemma but do have some experience with the Fog lamp wiring and 10 amp breaker.  A picture of my original ; marked 12v.  10a.  Bat. and AUX.  Possibilities, correct size amp breaker, hooked up correctly and a solid ground.  When fooling around with mine it seemed the breaker was just a pass through and would function either way perhaps for a longer term the Bat. side needs to be connected to the incoming/Bat wire ?  I hate electrical issues.  Brian

[midlife]

Those circuit breakers will work in either direction, IIRC.  To check for good grounds, use a digital volt-ohm meter on resistance setting, reading between the ring connector and the battery ground point.  Resistance greater than 1 ohm is not good. 

On a newly painted car, sometimes you need to scuff the paint beneath the ring connector to make a good ground contact.  Don't forget about the engine to firewall ground.

I do like the idea of finding where things get hot: the switch itself, the circuit breaker, the various bullet connectors, and the grounding point.  Where it is hot is usually where the problem lies/lays/damn English and grammar...

[67gta289]

  Where it is hot is usually where the problem lies/lays/damn English and grammar...

Pretty sure that the proper English would be something like "Whilst checking the circuits for proper earthing, heat is where the problem lieth" or something like that there

On a serious note though a high resistance (and corresponding heat generator) is not good, but it will not cause a problem if in series with the bulb load, it will only cause the bulbs to run dimmer.   High series resistance is not the culprit with high amps.  After all, the ultimate in high resistance is an open circuit such as a cut wire.  No current flow, no circuit breaker tripping.  But then again no lights either.  When I find a poor ground (and heat) I find that the lights don't work (or work to the proper intensity), not that the breaker trips, for all the reasons mentioned.

That said, any low resistance to ground (e.g. a loose strand with a sketchy path to ground through a painted surface) is in parallel with the bulb and if sufficient can cause the breaker to trip.  Any serious short to ground would cause the breaker to trip quickly up to and including what we would call "tripping free" and never closing long enough to notice downstream.

If you have a meter that can measure up to 10 amps, put it in series right before the bulbs, and see what the draw is.  Then move it to just after the switch, and compare.  Should be the same.  If the same, and less than 10 amps, and the breaker trips, you have a bad breaker. 

[WT8095]

What bulbs are installed? (part number or watt rating)

[Hipo giddyup]

 Thanks again Midlife.. and thanks John. I will do the test with my meter as soon as I have a few minutes. The car is newly painted but I use my cordless dremmel to "scuff" up the surface where a connection would be. I will definitely be checking the ground at the breaker itself as I know my pedal support is painted up as well. Maybe i forgot to scuff that good enough? I like the test of checking amperage at the bulbs and then at the switch. I'll let you know what I find.
Let me check on the bulbs wattage. I think they are 30w?? I do know they are GE bulbs and decent quality (they actually came in the kit I bought from VA  Mustang).

[WT8095]

Let me check on the bulbs wattage. I think they are 30w?? I do know they are GE bulbs and decent quality (they actually came in the kit I bought from VA  Mustang).

If they are 30W each (60W total for both), then you should be drawing 5A total. Same as midlife reported on his 66. I asked the question to rule out the possibility that you had too-high wattage bulbs installed.

[jwc66k]

1. With the battery disconnected, check each leg of the circuit from the circuit breaker with a ohm meter and inch by inch for an accidental ground (sometimes called a "short), the lead to the switch, switch, leads from the switch, connectors at the firewall, connectors at the lamps. Check the wires for something simple like a bolt, screw or a bracket pinching the wire.
2. The UL number for the bulb is 4415.
3. When the fog lamp switch is activated, the parking/running lights are added to the fog lamp circuit which increases the current draw. The 5 amp draw is now almost 8 amps (I wish there was a schematic for all this.)
Jim
Statement 3 is incorrect, the rear running lights and license plate light are added to the fog lamp circuit, but this still adds current draw.

[jwc66k]

Got one, a wiring diagram. I think I need to thank Veronica. I've seen this diagram in a Ford publication as well.
Jim
Replaced with a better copy.

[C6ZZGT]

I`m having this same issue on my 66 (always have since i put it back together) except that it flashes on and off in a regular manner not off for a minute and then back on.

[CharlesTurner]

Possibly something up with the headlight switch also...