blowing fuses, exterior lights not working!

[morbank]

I'm looking through the threads but can't find answers to my problem. I'd greatly appreciate insight from the experts...

We purchased our 1978 Scamp and fixed it up. The RV repairman helped us with a lot of things, like installing new marine battery, fan, but overall we didn't change the entire wiring.

He installed a 7-pin hitch on our Volvo, and we started blowing fuses. We realized we were driving without tail lights and side lights more than a few times! Then, last year we got rid of our Volvo and bought a Mazda, and RV repairman put a new 7-pin hitch on that car.

Plugged it in last week and all looked great. But when it was time to leave camping, none of the exterior lights would work. ALL were out. We looked for blown fuses again, found one fuse but it was intact. Still can't figure out why our exterior lights keep going out.

We have another trip coming up and need to figure out the problem. Replacing all the exterior wiring would cost $500+ and replacing everything would be $1000+ -- but cost aside no one even has the time to help us right now.We are thinking of investigating the wiring ourselves because we don't want to go back to the same guy.

Does anyone have suggestions? Could it be the ground? Thank you!!

[Byron Kinnaman]

Originally Posted by morbank

I'm looking through the threads but can't find answers to my problem. I'd greatly appreciate insight from the experts...

We purchased our 1978 Scamp and fixed it up. The RV repairman helped us with a lot of things, like installing new marine battery, fan, but overall we didn't change the entire wiring.

He installed a 7-pin hitch on our Volvo, and we started blowing fuses. We realized we were driving without tail lights and side lights more than a few times! Then, last year we got rid of our Volvo and bought a Mazda, and RV repairman put a new 7-pin hitch on that car.

Plugged it in last week and all looked great. But when it was time to leave camping, none of the exterior lights would work. ALL were out. We looked for blown fuses again, found one fuse but it was intact. Still can't figure out why our exterior lights keep going out.

We have another trip coming up and need to figure out the problem. Replacing all the exterior wiring would cost $500+ and replacing everything would be $1000+ -- but cost aside no one even has the time to help us right now.We are thinking of investigating the wiring ourselves because we don't want to go back to the same guy.

Does anyone have suggestions? Could it be the ground? Thank you!!

The exterior lights (side lights, tail lights, brake lights) are all controlled by the tow vehicle. Look for blown fuses in the tow vehicle. Depending on the vintage of options of the tow there could be separate fuses from the vehicle lights.
It could also be the connector is corroded, simply plug and unplug it a few times then try again.

[Jon Vermilye]

If you are not blowing the tow vehicle fuses, I'd look for a open ground since you noted all the lights were out. The only wiring common to everything is the ground. Chasing the connections with a multimeter is you best way of finding the problem. With the circuit on, at each socket & connector measure to a known good ground. You should see 12V on the hot side & 0V on the ground side. If you see 12V on the ground side, the ground is bad. Again, since all the lamps don't work, the problem is probably at the trailer or tow vehicle connector, or the ground connection in the tow vehicle or trailer.

One method I've found useful for checking for shorts (blowing fuses) is to remove the circuit fuse & replace it temporarily with a 12V lamp. If there is a short, the lamp will light. If the circuit is open, the lamp won't. A partial load on the circuit may make the lamp glow. In any case, while watching the lamp "wiggle" connections. When you find the connection that makes the lamp come on at full brightness, you have found the short.

As Byron noted, you need to do all of this with the tow vehicle connected since it is supplying the power.

[SilverGhost]

Which lights are not working? Trailer, tug, or both? Do they work on the tug before hooking up then quit? Do they work on the trailer for a short while then stop, or do the trailer lights just not work at all?

I ask because I had a bad trailer light converter (for imports with separate stop and turn lamps into trailer combined stop/turn) in my Golf that had similar issues. I chased trailer wiring for months on a couple trailers before finding the culprit.

A basic trailer light kit is probably $40 to $80 dollars and not more than a hour to install. The rest of the marker lamps and such add labor but not a lot parts cost (maybe double the basic kit). Of course that is not taking into account model specific lamps.

Jason

[SilverGhost]

One test idea (especially on newer computer controlled cars) is to disconnect the tug and use the trailer battery. Use simple jumper wires from the 12V contact on the trailer connector back into the other contacts for the various lights. I use a fuse holder with a circuit breaker in it and flat blade contacts on the wire ends. Obviously don't try this on the ground contact :oh!::

Jason

[steve dunham]

You can remove all the light bulbs from the outside fixtures , then take an ohm meter and (at the trailer connector) read between the Neg- ( white wire ) and the wires going to the brake , turn signal and running lights You should read infinity on the meter, if you get a reading it would indicate a shorted wire or a shorted or corroded socket

[morbank]

Ok, additional question--uh, what are brake coils? We see them on the diagram, and when we look under the scamp we see some various blue wires connected to the inside of the wheels--but one of the wires is just sort of "hanging" and not sure where the other wires are going to??? They don't connect to each other like in the schematic.

And we can't find where the white ground attaches to the frame.

To answer SilverGhost, before we left on our trip, we plugged into the two vehicle and all the lights, turn signals, etc. worked fine. But when we plugged in again to leave a few days later, no exterior lighting worked at all. The two hitch and connector is brand new. Our mechanic said that everything seemed in place on the tow vehicle, so considering we've had problems now with 2 towing vehicles, I suspect that problem lies within the wiring of the Scamp. ???

[Thomas G.]

Originally Posted by morbank

Ok, additional question--uh, what are brake coils?

The brake coils are elecromagnets that actuate the brakes. They are inside the brake drum.

We see them on the diagram, and when we look under the scamp we see some various blue wires connected to the inside of the wheels--but one of the wires is just sort of "hanging" and not sure where the other wires are going to??? They don't connect to each other like in the schematic.

Each brake should have one wire that is grounded and one that is energized by the brake controller. Either blue wire can serve either function.

And we can't find where the white ground attaches to the frame.

What white wire? The white wire from the plug at the front of the trailer?

To answer SilverGhost, before we left on our trip, we plugged into the two vehicle and all the lights, turn signals, etc. worked fine. But when we plugged in again to leave a few days later, no exterior lighting worked at all. The two hitch and connector is brand new. Our mechanic said that everything seemed in place on the tow vehicle, so considering we've had problems now with 2 towing vehicles, I suspect that problem lies within the wiring of the Scamp. ???

You really need to get a multimeter and check out the trailer. You can pick one up for less than $10 and there are many YouTube videos that show you how to use one.

[morbank]

Hi Tom-- Thanks for the info. The white wiring I'm speaking of is the ground wire. We've checked all the paths it takes from the pin connector, into the Scamp, to the marker lights, to the rear lights, etc. But is it actually supposed to ground somewhere? Or is the wire relying on the grounding provided by the harness in the two vehicle?

What does Jon mean when he says, "Look for an open ground?"

[Thomas G.]

Originally Posted by morbank

Hi Tom-- Thanks for the info. The white wiring I'm speaking of is the ground wire. We've checked all the paths it takes from the pin connector, into the Scamp, to the marker lights, to the rear lights, etc. But is it actually supposed to ground somewhere? Or is the wire relying on the grounding provided by the harness in the two vehicle?

What does Jon mean when he says, "Look for an open ground?"

You are on the right track. The tow vehicle should have a well grounded wire connected to the plug. The trailer should have the lights and brakes grounded to the trailer end of the plug. Unfortunately it is common to accomplish this grounding by grounding the lights and brakes to the frame and grounding the trailer plug to the frame. This leaves lots of places for the ground to corrode or break or have a poor connection (an open ground).

The first thing I would do is to run a long piece of wire from the tow vehicle ground to the trailer light socket. If things work, you know that the ground is interrupted somewhere in between. Long term, it is good to leave such a wire in place by passing the frame as a conductor.

[Thinh]

Here is my perception ab your problems: When a wrong connection is made with 4/7pin connector, without hooking up the trailer, no problem will be found out or even with trailer hooked on, your problem will only be shown up at the first brake/turn...signal applied. When +12VDC is connected at wrong pin, your RV exterior lights won't work and you are lucky when having none of blown fuse and bad luck when having one blown fuse in your TV(battery fuse). Here is my simple testing for first, RV at hitch connector and secondly for TV. Unhook your RV separately and using an external 12VDC supply to do the test. Ground this supply to trailer frame then one at a time, feed +12VDC at each pin. This process will show you which side, light/electric brake of your RV works or defects then go from there to replace or checking RV fuse/connection..ect... If everything is OK then your problem will be definetely from your TV..i.e...WRONG PIN CONNECTION. If that is the case, do the same thing at your TV connector, either with help from friend to read voltage when you are inside TV applying Lt/Rt turn/brake, night lights...or diy with a 12VDC bulb connected to the pin, one at a time and see it yourself when you are at driver seat to activate signals..I strongly suspect you have a wrong pin connection in your 7pin connector and good luck.

[morbank]

Thanks Thinh-- I took apart the 7 pin and inspected it. The colors are attached correctly. However, the colors of the wires in Scamp aren't matching! Furthermore, the basic 7pin diagram that I am finding on trailer sites don't match the basic wiring on the Scamp diagram. For instance, on basic diagrams, yellow is RT, Brown Tail, Green RT. But on the Scamp diagram, brown only goes to Right Tail, Yellow goes to both. Can someone please explain to me (use simple words please!).

This is the diagram I've been looking at: Wiring Color Code for a 4 Pole Flat Vehicle Connector | etrailer.com

Please help! My husband is about to quit. He's gone to the store 2 times already. Thank you!!!

[Jon Vermilye]

eTrailer has a better set of wiring schematics here.

When I added an upper set of trailer lights to my Escape trailer I discovered that Escape changes the color scheme once inside the trailer. The pins on the connector are wired to the functions shown in eTrailer's schematic, but they use brown for the right turn signal/stop light & green for the taillights. On further examination, I discovered that Scamp does the same thing. Why? I don't know, but that may be your problem.

[morbank]

Yup-- I just made that revelation. Found another helpful forum post that explains that. So I am going to open up the box connecting the 4-pin to 7-pin and make sure that the yellow gets becomes red, brown becomes green, etc. I'm either a genius or a complete idiot. Wish me luck.

[morbank]

OMG-- Mazda installed a flat 4 to which my RV mechanic converted to a 7-pin. But the standard hook-up kit that plugs into the lights of the Mazda is an original 7 wire!! So now my set up goes: 7 -pin down to 4-pin back to 7-pin. I really am going to shoot myself, or someone else maybe...

I am going to have to assume that because the transition boxes/plugs are standard issue, they've been connected correctly, and I am going to stick with the color codes on the 7-pin as designated on this forum: http://www.fiberglassrv.com/forums/f...ion-57709.html

[morbank]

Someone please help!!
We rewired the Scamp, hooked up green, white, black, red, (not using yellow or blue), and tested it. It worked! We took it for a test run, but realized I had made the length (from Scamp to plug) a little too short, so I had to cut the wires, and reattach more wire length. Now I've plugged it in twice, turned on the car, and have blown fuses both times. they are 15amp fuses where the hitch connected to the rear cigarette lighter (already checked and it's ok to do that).

So, did I make a bad connection? Which wires would be most likely to cause fuses to blow? I checked the colors of wires and they are all connected correctly....

[Joe MacDonald]

how did you re-attach the wires? if you crimped them together,(with the wrong type of crimper) you could have caused a bare piece of metal to come through the crimp, and it could short out on another wire, or it could ground out, alternately it could be a stray wire sticking out and grounding against chassis

[morbank]

Ok....well I still need help! We checked all the connections, and I did find a loose wire. After that, everything lit up fine. We went for a test drive and the camper stayed lit the whole drive. Then we turned off the car. When we started it again, the fuse was blown! We changed the fuse, and it started right up again. So this time when before we stopped the car, we pulled out the plug. Turned off the car. Then plugged it back in and the fuse was blown!

Does anyone know why the fuse blows when the power is disconnected??? Thank you!!!

[chris loewen]

I don't know if this will help but I had a similar problem with my '76 trillium and after checking everything it turned out to be a faulty bulb that was shorting out and causing my fuse to blow. I got confused because that bulb wouldn't blow and would light up again when a new fuse was put in. I undid all the bulbs, turned the power on and started screwing in a bulb one by one to find the culprit. Oh my god what a relief to find that out and such a simple solution after so much stress. Not sure if this will help but maybe worth a try???

Chris