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Trailer Hitch and Wiring on 740

marshcat

marshcat

New member
Joined
Feb 10, 2008
Location
Cambridge, MA
I am interested in putting a trailer hitch on my 1992 745TI. How difficult is it to install the hitch?

More importantly, how would I go about wiring the hitch? With domestic cars, you can just splice the wires into the existing wiring. I have head that Volvo's do not respond positively to this type of wiring. I have heard that the extra amperage needed kills the electronics on the car.


Dan
 
marshcat said:
I am interested in putting a trailer hitch on my 1992 745TI. How difficult is it to install the hitch?

More importantly, how would I go about wiring the hitch? With domestic cars, you can just splice the wires into the existing wiring. I have head that Volvo's do not respond positively to this type of wiring. I have heard that the extra amperage needed kills the electronics on the car.


Dan
Click to expand...

The hitch is easy; it bolts right on.
The wiring is easy, too, IFF you know what you're doing.
My '90 765, and maybe your 745, too, has a rear bulb-out relay, which is nice 'cause you can splice into the wiring BEFORE the relay.
All cars respond poorly to bungled wiring.:-P
 
In regard to the 7/9xx series:

1. It's easy to install. 6 bolts and yer done. (you may have to pull and modify/leave off the stock rear trim if you have one, also easy) This assumes OEM hitch (I highly recommend) or oem mounting based hardware (I have one from Uhaul that uses stock bolt locations) all the bolts should already be on the car.

2. I use a standard trailer light adapter from autozone on mine. I've never had a problem with many different kinds of trailers. It does piss off the bulb warning "relay", and i suppose it might encourage it to burn out a little faster, but that's nothing a little solder can't fix.

In summary: It's easy, and don't worry about the light adaptor.
 
You have a wagon, so: I simply connected all the wiring on the rear left side (where the harness enters), splicing into the mains. I ran one wire through the "middle" compartment and into the right one, for the right turn light. I simply keep the whole trailer light plug and wiring in the rear left compartment with velcro. When I need to tow something, i just stick it out the trunk, then close the trunk on the wire at the appropriate length. Once done, i just hide it back in the compartment. Works great.

Actually, when I had my 764Ti, I still just ran it out the trunk. :)
 
I live in the most part-unfriendly part of the country. Or rather, there are plenty of new parts but few used. We have FCP Groton though :)

There are no pull-a-parts for like 100 miles.
 
Ask here in the wanted section. I'm sure someone has a spare or one they would be willing to ship to you. :)
 
brake lights/running lights

so the trailer wiring harness I bought has wires for right turn, left turn, brake/tail, and the ground, how do people splice the tail/brake light since the 740 has two different wires for a running light and a brake light.
 
I just put a hitch on my 940. I ordered it from here:
http://www.drawtite-hitches.com/

they matched the best price I could get on the web, and if you spend more than $150 you get free shipping. The package came with a draw bar, all you need is a ball and your wiring.

I used one of these units for the wiring. Its powered off the car, so there is no draw on the actual lighting system. I ended up pulling a feed from the fog lamp circuit as its s 35amp circuit on my car.

http://www.drawtite-hitches.com/products/Trailer Light Power Module,118187

The hardest part of the whole thing was dealing with the rear facia. Mine was a pain to get off. I ended up trimming it and re-installing it.

All in all - not a bad deal.
 
There's no need to wire it before the bulb relay. I've wired straight to the tail-lights with a converter box, and never had a problem on 5 or 6 different 200/700 cars...
 
I will +1 the idea of wiring at the taillights. You just have to get used to the bulb-out indicator being on when the trailer lights are on. I used piggyback spade connectors so there was no interfering with the original wires at all. Just remove the wire from the tail light, put the pb conn on the light, reattach the original wire and then attach the appropriate wire that goes to the converter box - easy and easily reversible. Sometimes they are hard to find though. If nowhere else, I think the Canton Napa carries them.

As for the trimming, if you don't care what it looks like, I imagine it will be very easy. Again, I am one for reversability though, so I cut a flap for the receiver to go through. I took nothing off of the valence at all. I just cut three sides of the rectangle. It is kind of a pain, a required taking the valence off a few times to make sure the measurements were right, but it doesn't look like a hack job like so many Volvo trailer hitch installs.

The valence can be seen HERE.
 
posaune said:
It is kind of a pain, a required taking the valence off a few times to make sure the measurements were right, but it doesn't look like a hack job like so many Volvo trailer hitch installs.
Click to expand...

I always just remove that thing all together...... I guess that's what you mean by a "hack job"?
 
casioqv said:
I always just remove that thing all together...... I guess that's what you mean by a "hack job"?
Click to expand...

That would be it :-P.

My 245 had that done (before I bought it). It is easier to do that, yes, but it *looks* like the plastic was just cut for room. It also gives a clear view of the [usually] rusty rear muffler. It isn't that much harder to make it look like the trailer hitch is supposed to be there.

Of course if you don't care how it looks, I suppose it makes no difference.
 
Sorry for the thread necro-revival but it made more sense than starting another new one. Installed a 4 flat harness on my 745T using the piggyback connectors as described above. I have no lights on the PS at all, and only tail/brake on the DS, no signals at all.

I used a non-powered harness and some googling of trailer supply sites leads me to believe I need a powered harness? Any thoughts on where I am going wrong, or do I in fact need the powered harness. I can live with the bulb out light being on if that's all the powered harness fixes, right now I just need some lights on the trailer. TIA.
 
I've put these on 5 cars, have not used the 4 pin, there aren't enough pins. Without looking I think the ones I am now using have 6 pins, one is free.
I have gone to the powered units as they do provide brighter trailer taillights, but non-powered do work.
 
Good to know that the powered converter isn't necessary, although I may get one for the brighter lights. As for the 4 pin converter I installed it has the following pin outs:

White = Ground
Red = Brake
Green = Right turn
Yellow = Left turn
Brown = Park/Tail

On the 745 I just used the piggyback spade connectors on the existing vehicle spades and then hooked the stock wire connectors on to the spades where they were hooked before. I even swapped the two wires to the park/tail and brake spades and nothing changed, the turn signals are pretty hard to switch, lol. What extra wire did you use on the 6 wire converter?

Right now it seems like I have everything plugged in that I should need so still stumped? One last thought is this is a Canadian spec car and has the first year DRL's, really can't see that affecting anything but thought I should throw it out there.

ETA: The trailer has no brakes so I'm only working with wiring for lights.
 
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