I have a 1990 Volvo 745 turbo.
Bought last year and have since been resurrecting it from the dead.

The horn has never worked which I think is ok but kind of dangerous.
So I checked the connections at the horn side and the steering wheel with a volt meter. Now if I did this right that means the wires have connectivity so there ok? I'm thinking maybe the relay is no good but how would I check that?

Also because my diagnostic skills are lacking when it comes to electrical devices any tips about how to trace this down would be great.

Thanks to all,
Greg

 

The bad horn of the Volvo 740 and 940 is a very common fault. The horn lies in a very bad place and gets filled upp with crap and leads to its downfall. Just get a new one from the market and replace it or try spraying a lots of oil in and around the horn. And it may jump to life and work like mine did.

 

to verify its the horn itself, disconnect the wires from the horn, hook them up to a volt meter, and have a friend honk it... if you get 12V, then its the horn, and yeah, you can replace with most any horn that physically fits and has compatible connections. Hella Supertones or Fiamm "Freeway blasters" are great for clearing the road in front of you each of these should be a 2 horn high/low tone set, which are best used together (wired in parallel). 'freight train at 500 feet' is one description of the supertones

 

If you buy a new one you could change its position. Move it inside the grill where its less prone to decay from outside.

 

horns are fairly directional. they should be pointing forward and maybe slightly down (so the sound bounces off the ground for farther reach). on the 240, they are mounted on a bar right in front of the radiator behind the grill, thats optimal. I haven't looked where they are on the 740/940, but I'd assume pretty similar ?

 

Ok so it was a busy couple of months, time away from helping the car.

Checked the horn connections and no juice registered on the volt meter.
Now what? The fuse I can examine but how can I check the horn relay?
Then I suppose I'll have to chase the horn wire through the harness?

I noticed under the dash that the stereo has been hacked before.
Although the original radio is in now, it must have replaced what ever they used before.

Any common problem help would be great.
Thanks Greg-

 

horn button has blue-black wire to pin 17 of the big block firewall connector near the left A post, this wire goes to the horns up front. the horn button connects this blue-black wire to ground when you push it. the other side of the two horns is yellow, and comes back through pin 4 of the same A post connector, it is connected to the wiper switch pin 3 and to fuse 15, the other side of fuse 15 goes to the ignition switch pin "X" (powered in accessory or ignition on)

that should be enough to trace the circuit. if the car is switched on, there should be power at the yellow wires at the two horns up front, so if you ground the other side (blue-black) of the horn it should honk. if it doesn't, find that big block connector and see if there's power at pin 4 (yellow wires on both sides). if there isn't, check if there is power at the yellow wire on pin 3 of the wiper switch, then at pin 15 of the wiper relay in the main relay panel, then at fuse 15.

if there IS power at the horn yellow wires, then, check to see if the A post connector pin 17 is hot (since it should be powered through the horn) and if grounding it with a jumper wire honks the horn. if not, the blue-black wire under the hood is broken, if yes, then verify that grounding the metal ring under the steering wheel honks the horn, and if not, its the wire between htat and the other.

oh yeah, be careful, very careful, around the airbag wiring.

 

This is seriously the best answer to a question I have ever received in a forum. But I'm afraid I did not understand a word of it. I will try to reread this a few times and get the sense of it before finding the problem with the horn.

Thanks Pierce,
Greg

 

Simple answer - get a voltmeter and put probes across the two wires going to the horn. Have someone in the car press the horn button. If you have voltage when the horn button is pressed, then replace the horns. If you don't, then start tracing the wires back to the horn button. Pierces answer should help in that.

 

Ok so the old horns were crusty and needed replacement.
Bought new ones and there is no voltage at the horns.

Started to trace back and found a rats nest can anyone tell me what we are looking at here? Did 1990 Volvo's come equipped with an alarm?

I traced the wires up visually but can't seem to work the volt meter correctly.
Found a blue plug to nothing. Hack job of wires to a horn. Wires that lead to an alarm of some kind I think? And a birds nest of wires not connected which then go through the fire wall. I have more picks to come but welcome comments.

 

that blue 2-pin connector might be the auxillary starter connection for mechanics use.

that horn and other stuff most certainly looks like aftermarket added crap (maybe dealer, maybe Jose's Alarmingly Bad Car Stereo and Alarms). *UGH* I hate aftermarket alarms.

 

Ok, that's what I thought.

So perhaps I will follow those wires through the fire wall and see where they are connected. I am thinking that will be where the horns are disconnected. I Will post more pics of what I find. Thank you Pierce, as always you are a most gracious helper!