On my 88 745 when I press the horn buttons the horn does not sound, but the real wiper activates. If the steering wheel is turned about 30 degrees in either direction the horn will sound, the wiper action happens when the wheel is mostly straight ahead. I guess my Volvo is just trying to be kind and waving instead of making a noise. :-)

I took off the steering wheel today and tried to clean the ring that the horn switch button makes contact with. There was no change in behavior.

Any ideas?

-David

Once again the Brickboard is correct. I wiggled the steering column while pressing the horn button and sure enough, the horn sounded. So I guess I will have to remove and replace those theft deterent bolts. I think I have some left handed drill bits which should be about the right size.

Thanks for your help, as always.

-David

I believe cancerman is probably correct about the bad ground. This "horny wiper" problem is a fairly common one on the 740's. A typical problem is that two bolts that anchor the steering column to the dash structure work loose slightly, causing: A.) A bad ground, hence the various electrical accesseries feeding back into each other, and B.) A looseness in the steering column that you might detect when turning corners, or if it's real bad you may even feel it by yanking the wheel vigorously from side-to-side.

When you said the problem disappeared temporarily by turning the wheel, it makes it sound like that's your problem. Access to the (2) mounting bolts is gained by removing the knee bolster. The factory used shear-head bolts when originally assembled, I'm told as a theft deterant, so in order to replace them they need to be drilled and removed with an easy-out. They should come out pretty easy though, as they probably aren't very tight any more. They can be replaced with regular hex head bolts. Someone advised me to remove and replace one at a time so that the piece over the top of the column doesn't stray from home.

I'm almost absolutely sure that the ground to the steering wheel is faulty.

The first thing I would do a continuity test between the middle of the steering wheel (under the pad) and your favorite chassis ground. I prefer the outer ring of the cigarette lighter. Remember to put the steering wheel in the streight ahead position. While you're at it, check for continuity between the metal on the outside of the ignition key and the inside of the steering wheel, and the ignition key and your chassis ground.

I'm not sure where the steering column is grounded from, but I would give the universal joint where the steering wheel bends under the hood a good blast of WD40 and spin the steering wheel all the way side to side for a few turns to see if that helps.

If it dosn't, I would get a Haynes manual for the 1982-1988 740/760 and follow the instructions for removing the steering column. The ground is likely part of the bearing that supports the column.

(Other brickers - If I'm leading this gentleman into the dark abyss of confusion, please correct me.)

I hope this helps you somehow. I had typed a long shpeil about removing fuse 15 and turning the front wipers on, but after beating my head on the horn actually *failing* with it's super-simplicity, as well as it all being related to the steering wheel position, the only think that makes any sense is the column ground going south.
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89 764 GLE 150k/ 86 745 GLE 240k

it would seem the wires from the horn and the wires from the wiper arm are crossed or shorting each other out or something. Did you try tracing them to teh ground and checking to see if its corroded or lose? I'd give you a hint but I've never needed to trace these wires...

Pull the panel under the steering column and follow the wires. Maybe the grounding poles on the ECU?

-rt