Trailer wiring for a Porsche

[VaSteve]

I need to wire up my little Harbor Fright trailer. The harness I have has 4 leads. It's a standard harness. I lost the directions, so I was using this as a guide:

http://www.accessconnect.com/trailer_wiring_diagram.htm

I can't figure out how it can tell the difference between the brake and "tail light" illumination or the turn signals since Porsche uses a separate yellow bulb (unlike an American car where I had this hooked up before). Does the car give more power to the bulb when the brakes are applied? I always assumed it was two separate elements...

I was using this Rennlist post as a guide as well, but I'm having brain failure here.

http://forums.rennlist.com/rennforum...91&postcount=8

[javadog]

It is two separate filaments.

I'm no further help.

JR

[javadog]

Okay,

Your Rennlist link isn't working.

It seems that the grounds from the lights on the trailer diagram are not shown. I think you need a five-way connector. Thus:

Ground
Tail lights
Brake lights
Left turn signal
Right turn signal

Remember, older American cars had the tail light and turn signal related to each other. The turn signal was just the tail light blinking on and off, if my memory is any good. I have no idea how they wired that.

JR

[onewhippedpuppy]

Buy a truck? I know, I'm helpful.

[wilke3169]

I once had a Nissan pick-up. It required an adapter to wire normal trailer lights. Bought it at the local hitch shop.

[VaSteve]

Originally Posted by javadog

Okay,

Your Rennlist link isn't working.

It seems that the grounds from the lights on the trailer diagram are not shown. I think you need a five-way connector. Thus:

Ground
Tail lights
Brake lights
Left turn signal
Right turn signal

Remember, older American cars had the tail light and turn signal related to each other. The turn signal was just the tail light blinking on and off, if my memory is any good. I have no idea how they wired that.

JR

Yeah, that's what I was thinking, it's missing something. But would that mean that I'd have to rewire the whole trailer as well?? I know people use trailers with their Porsches... Hmmm.

[javadog]

Originally Posted by VaSteve

Yeah, that's what I was thinking, it's missing something. But would that mean that I'd have to rewire the whole trailer as well?? I know people use trailers with their Porsches... Hmmm.

Yes. You'd have to run 1 more wire to each rear light.

JR

[red911sc]

Was planning on doing the same thing. I have a small Harbor Freight trailer half assembled in the garage (has been that way for a while). I may be able to find the directions (if it is the same trailer), scan in and e-mail. would this work in lieu of a direct answer?

[wilke3169]

With the adapter the trailer wiring stayed the same. Was a solid state device that combined the signal. Nissan had an amber turn signal and red stop light. Trailer was a normal 1157 bulb.
http://www.etrailer.com/y-8.aspx

Doesn't list Porsche but half way down the list is the device and wiring.

[Tom '74 911]

Originally Posted by wilke3169

With the adapter the trailer wiring stayed the same. Was a solid state device that combined the signal.

I'm just starting this on my '74 911 to tow a tire trailer to the track. I'm unclear about the brake wire and what to connect it to. The 4-pole directions mention:

1. right turn signal
2. left turn signal
3. ground
4. taillights

What about the brakes? Do I need a box to combine the brake wire with the turn signals or can I just bundle the brake wire and turn signal wires together?

Thanks,
Tom

[Tom '74 911]

Sorry for the second post - do I need something like this:

http://www.etrailer.com/pc-VWH~20251.htm

Thanks,
Tom

[rick-l]

Is the filament for the brake the same one as the turn signal?

Originally Posted by Tom '74 911

1. right turn signal /BRAKE LIGHTS
2. left turn signal /BRAKE LIGHTS
3. ground
4. taillights

Ooops. A quick check of the (82 is all I have) wiring diagrams show you have a seperate bulb for the turn signal and the brake light.

So more wires or some logic

[rick-l]

Now I'm curious. How do you handle this?

The only cheap solution I could think of is a relay that turns the single stop light / turn signal on that side of the trailer off when the turn signal is on so it would be the inverse of the back of the car.

[Tom '74 911]

Now I'm curious. How do you handle this

I don't know. . . that's why I asked! My car has separate wires and bulbs for the brake lights and turn signls - as you mentioned. I think the link I posted is for a converter type box that combines those 2 signals to one - but I'm not positive.

Tom

[VaSteve]

Originally Posted by Tom '74 911

Sorry for the second post - do I need something like this:

http://www.etrailer.com/pc-VWH~20251.htm

Thanks,
Tom

Yes. I went to pep boys and bought something like that to make the electrics work.

[Tom '74 911]

Thanks for the info Steve.
Tom

[rick-l]

Originally Posted by VaSteve

Yes. I went to pep boys and bought something like that to make the electrics work.

There wouldn't be a schematic showing what is in the box would there?

[VaSteve]

Originally Posted by rick-l

There wouldn't be a schematic showing what is in the box would there?

The magic box? No, I don't think so, but I pitched the package. It's probably full of diodes and other common stuff. It's probably $.50 worth of electronics sold for $30.

Sometimes stuff like that has things printed on the outside. I'll look tomorrow.

[VaSteve]

I checked. There was nothing printed on the outside of the box. Sorry.