Odd breaker-switch failure mode ? Comments please

This past weekend I pulled my RV out of the hangar to do a series of test runs in preparation for the first flight.

The first run-up went well with all indications reading normally.

While waiting for the engine to cool back down for the next run I left the plane out in the sun with the tip-up canopy closed and no canopy cover in place.

After the engine cooled I jumped in and proceeded with my pre-engine check list only to find out the 5A breaker-switch for the fuel pump would not turn on. I suspected it might have overheated in the closed cabin because everything in the cabin was HOT to the touch. (Note: all the remaining breaker-switches functioned normally.)

The engine started without the electric fuel pump and I was able to do my second test run of the day. After completing the test run, I pushed the plane back into the hangar and after cooling off the breaker-switch functioned normally.

I have ordered a replacement breaker-switch and will change this one out.

Here is the question, is this a common mode of failure for these breaker-switches?

[Please do not turn this into another breaker vs. fuse debate, there are enough threads dedicated to this top already and I have made my choice and will stick with it.]

How hot could the breaker have gotten? Maybe it's possible, and maybe it's just a bad breaker but my first instinct would be to assume the breaker tripped for a reason and double, triple and quadruple check that there's nothing wrong with the wiring or the fuel pump.

You can take the old breaker and heat it with a hair dryer to see if that causes it to pop. That would be an interesting experiment.

Hi Bill,

Can't address the breaker/switch directly, but I have had a straight breaker that was mounted directly under a black-painted glareshield pop when left out in the sun - and yes, it was VERY hot (not from current flow). Since these are thermal breakers, and pop when they reach a specific temperature, I figure that if they start at a higher temp, they will pop at a lower current (to put it very simply).

I keep meaning to go look up the specs on that specific breaker, but haven't gotten around to it (it's not a critical circuit for me) - you might check the specs for the one giving you problems.

Paul

jcoloccia said:

How hot could the breaker have gotten? Maybe it's possible, and maybe it's just a bad breaker but my first instinct would be to assume the breaker tripped for a reason and double, triple and quadruple check that there's nothing wrong with the wiring or the fuel pump.

You can take the old breaker and heat it with a hair dryer to see if that causes it to pop. That would be an interesting experiment.

Click to expand...

John,

It is possible but not likely that there was a wiring issue as the switch was off as was the master until I got into the plane for the 2nd test run. Even with the master off, you couldn't turn the breaker-switch on. This is why I think it is temperature and not current related. As Paul pointed out, these trip on temperature, usually caused by current not sun.

I did try another 5A breaker-switch at the same time I had the problem with the fuel pump and it worked as expected.

You have a good idea regarding testing the switch with a heat gun, after it is replaced.

Yes, absolutely these things are thermally tripped. I'm just surprised it could really get that hot. Wow.

heat tripping breakers

I've seen weak circuit breakers get hot and trip from being in the sun on boats. Replace the breaker.

Bill,

I had exactly the same problem before my first flight. At the time I thought the problem was the fuel pump! It turns out that the breaker/switch was defective. When I throw the toggle arm to the ON position, it would not lock(the toggle arm would stay at the ON position but with no electrical contact). Heat was definitely not a factor in my case. Van told me that I have to contact the manufacturer for a replacement. Unfortunately, manufacturer would not reply my inquiry. After replacing it with a new one I have not had any problem for the last 210 hrs. I played with the old one several times (move the toggle arm up and down, sometimes it would not even lock in at the ON position) and it began to lock again.

I also had a defective 5A pull breaker for my alternator IGN wire. After pulling it out then push it back in, it did not lock. It happened during my phase 1 and it took me to replace the alternator to find out the true problem.

After getting two defective breakers within one week I should have gone out to buy a lotto ticket.

Bill,

I had a toggle switch problem yesterday afternoon. I have a 10 amp toggle for my radios. I would have to flip it up several times before it would stay up. This was the case with either the master on or off.

I'm in south Texas and the day was sunny and plenty hot. However, I don't think the heat had anything to do with it. I went flying and once the toggle was in the on position, it stayed there with no problems.

I replaced it this morning and it does the same thing out of the plane. Believe it is just a lemon.....I hope!

Deal Fair
N34CB RV-4 flying
George West, TX

Gang,

Thanks for all the info.

After posting this, I sent Fabian at Affordable Panels a note asking him to send me a replacement and to invoice me for it. I also explained what happened and asked him if he had heard of this before.

His reply was that a replacement was in the mail and to return the defective breaker when it arrives.

Now that is customer service!

However, I think I will write him a check and test the breaker with a heat gun.