Blowing Brake Light Fuses

[Ray Kaminsky]

We have a 2007 Beaver Contessa with a brake controller and a Roadmaster Tow Dolley for our toad vehicle.  We frequently blow the 15amp brake light fuse.  We also occasionally blow the rear running light 15amp fuse.  Also have replaced the left rear tow dolley turn signal 1157 bulb several times in past year. Camping World checked and found no shorts in tow dolley.  Anyone else that has had this repeated issue and found a solution?

[LEAH DRAPER]

I keep blowing the brake lite fuse also on my 2008 Contessa.

Have no answers either......the brake lites on the toad still show, but the Motorhome blows.

[Ken Buck]

We tow a Ranger pickup or a Chev Malibu with our 07 Contessa and the only problem with lights was the turn signal flasher unit went bad.  Replaced it with a new unit, and have 3000+ miles, with no further problem.  (12,000 +/- miles total)

If you find what's causing your problem, please advise, just in case ours starts the same thing.

[Edward Buker]

This is a clamp on DC/AC amp meter that allows you to measure DC current without breaking the circuit. http://www.sears.com/shc/s/p_10153_12605_03482369000P?mv=rr&i_cntr=1304190491624

 If you do not have one but have a DC amp meter that is capable of measuring 20 amps then you will need to create a fused test jig using one of these fuse holders  http://www.radioshack.com/product/index.jsp?productId=2103778  or if you can wire the meter in series with your current motorhome fuse holder, whichever is more convenient.  You may be able to get some idea of the DC load using the coach monitor system but it may not be very accurate or it may only measure the house battery system.

You then need to measure the current that the coach normally draws for the circuit that blows the fuse. Then add the toad or tow dolly lighting and see what it draws. If it approaches the fuse value then your circuit just is not robust enough to handle the current load. You would want the voltage on the chassis batteries to be near 14V while you do the measurements if possible.
Poor connections at a socket or plug may exacerbate the problem. If the current is 12 amps or less total with the toad connected then try wiggling the plugs and bulbs one at a time, seeing if you can make the fuse blow. If so correct the cause.

Because multiple owners have the problem I'll assume that you need more current capability. What you would then need to do is wire in a new relay circuit. The relay trigger would be fed by the current brake light circuit. The 12V feed could be picked up from the battery bay with the appropriate fuse placed in series with the 12V line. Use a fuse and wire size that accommodates twice the current load that is drawn by the circuit that you are adding. Wire size should be at least the size used for the motorhome brake light circuits. Relays and sockets are available at automotive stores. This is an example. http://www.amazon.com/RELAY-BOSCH-30AMP-SPDT-12V/dp/B001JT016Y. This relay would be what feeds the toad or dolly brake lights and would be wired into the coaches tow socket brake light plug pin. The existing motorhome brake light wire to the toad or dolly plug would be disconnected.

One other alternative. If the total current being drawn (toad and coach) was somewhere near 15amps, or up to about 18 amps, you could ask Monaco if the wire size and harness is sufficient to replace the existing 15amp fuse with a 20amp fuse and see if they will approve that change.

 This added relay method can be applied to tail light circuits as well as the brake light circuits as needed. Hope this helps.

later Ed

[Tim Westman]

Ray,

It apparently is a "problem" with the Contessa.  I have had a similar experience and know of several other units with the same issue.  I was told that the wiring is good for 20 amps but I haven't tired the higher fuse yet...I still have a supply of 15's!  When they run low I'll give that a try.  I understand that the higher rated fuse may not be the solution from those that have already switched.  Good luck.

Tim

[Robert Mathis]

I was blowing mine also, and found a stray wire in the trailer connector plug (male end on Toad) that was occasionally shorting out. i have not had a fuse blow since replacing the plug.

[LEAH DRAPER]

I had to have the toad plug replaced after the wiring  by BCS because the connection pulled loose and I "drug it to death".  Was not aware of any problem  until I did that.  Had it replaced and maybe that is where my problem lies.  Will have to check it out.

Gerald,
What would be your take on using a 20 amp fuse v s. the 15 amp.

Leah

[Gerald Farris]

Leah,
I would not have any problem with running a 20A fuse instead of the 15A that was originally installed. However increasing the fuse size will only be of benefit if there are no problems in the system like an occasional short.

If the system normally runs in the 15A range, and that is causing fuse failure because the fuse is running so near it's maximum operating range, going to a 20A fuse may correct your problem. But if you blow a 20A fuse you need to repair the system.  

Gerald

[LEAH DRAPER]

I found (finally) the fuse that was blown.....there are several labeled  brake light(s), the offending fuse was in position F81 for my coach.  Also learned to my surprise that the engine had to be running to get brake lights to light.  That is not what I would have expected.  I replaced it with another 15A, but if it blows again will replace with a 20 A.

[Gil_Johnson]

My brake lights work without the engine running.

I too discovered I was blowing brake light fuses after replacing a bad brake light bulb.  What I discovered is a manufacturing defect in the wiring harness going to the bulbs.  The bulb contacts inside the bulb housing are designed to move in and out through the springs that keep pressure on the contacts.  The problem is that the wires going into the bulb holders does not allow for the free movement of the wires inside the bulb holder.  I'm sure the wires are installed tight to prevent moisture intrusion inmto the bulb holder.  Because the wires aren't free, the contacts will tend to move with the turning movement of installing a new bulb.  This looks to be a problem that will only affect the multi-element bulbs, i.e. brake and tail light light bulb. The one contact (brake signal) will short to ground and blow the fuse.

As for the current being drawn, the brake element in an 1157 bulb draws 26.8 watts or 2.1 amps @ 12.8 volts.  So, the coach has 4 bulbs and the TAD may have up to four additional bulbs.  With 8 bulbs and at 12.8 volts the current draw would be 16.8 amps plus the minimal current draw of the 3rd brake light on the coach and RV.  My intent is to replace the 1157 bulbs on the coach with LED equivalents.  This will bring down the current draw on the coach from 8.4 amps plus the third brake light to less than 2 amps plus third brake light.

For those that are towing a vehicle with four 1157 brake light bulbs, you MAY want to remove one brake light bulb from each side of the coach or tow vehicle.  This will certainly bring your current draw down to well below 15 amps.

Gil
08 Contessa 42

[Sean Donohue]

Just to keep this problem documented, I too have a fuse blowing issue when the toad is connected. I will try your suggestion Gil and also check with Volt meeter when I get home.  I had mulltiple fuses blow... turn signals flasher unit and brakes. I will post the offending fuse numbers when I get back to the coach.  

[LEAH DRAPER]

Why could you not just replace the 15 fuse with a 20 amp fuse?

[Jim Shaw]

The wire that is used  needs to be large enough to carry the current for the higher amp fuse.

[Steve Jewell]

Be careful putting a larger fuse in. When wires are overheated they may cause fires. I have seen many vehicles totaled from fuses that were to large. You need 12 guage wire for a 20 amp fuse. If the wire is longer than about 60 feet it will need to be 10 guage.

Steve J

[Jim Nichols]

  The 1157 bulb socket insulation does not move in a twisting motion when the bulb is inserted, only up and down (spring tension) to keep contact with bulb. If it is twisting as you explained it needs to be replaced as soon as possible.   If you are not having issues with the coach but only when connected with car please recheck your cord ends going into coach and into your car. the wires can come loose over time. Hope you already considered this and have it resolved.