Hi all. I have an 04 C70. I'm going to install the trailer wiring. Im using a system that supposedly only uses the signal from the car's tail lights and uses the power from the battery to power the trailer lights. My question is Im wondering if rather than run a wire all the way to the battery if I could tap a thiker wire in the trunk area for power? There is a plug in the trunk area by where the CD changer should go and there is a black and a yellow thick wire and on the other side of the plug two red thick wires. Also there is a gray with red strip wire that also looks pretty thick. Anyone know what these wires are? And if I should tap into them?

 

I used on a Euopean vehicle a solid state unit that was quite inexpensive and a snap to install with no wires going to the battery. A Volvo however will trigger the "light out" dash warning simply because you are pulling voltage/resistance that the brain reads as a lamp out. Check with your local trailer hitch shop for one of the units I spoke of.

r.

 

I bought a modulite unit not sure if its solid state but because of that dash light going off it supposedly is suppose to draw power from the battery. I found the OEM trailer wiring plug and checked tested the leads for the left, right, brake, and running lights and they are all there. Im wondering if I can just tap the +12v wire for the modulite unit from there as well. I figure if it is meant for a trailer it should be able to handle the power requirements. Any thoughts?

 

Merlinx I'm afraid I don't have the answer for that. Quite frankly I was not aware that Volvo was pre-wired for a trailer. It would seem that since it is wired then you could tap into the lead.............it certainly would not hurt to try. The autos that have separate tail lamps from turn signals was the big issue some years ago and hence the electronic unit. Now the autos have the ability to determine when a lamp is out and that was my concern. Interestingly when one places a copper based bulb in a BMW the indicator lamp will light as the resistance is different from that of a silver based bulb.

r.

 

OK I tapped in to the trailer plug for the modulite unit feeds and there was a yellow plug next to the trailer plug going nowhere with a pgrey wire with a red stripe. I tapped into that one for power and everything seemed to work I hooked it up no a trailer and no problem. One think did puzzle me. When I got home and parked the car I put the e brake on and put the top on shut the car off and noticed the brake lights were still on. I tapped the brakes and the lights went off. This is with out the trailer being hooked up. Im wondering if I need to put in a diode somewhere in there or if it was a fluk