V40: Horn relay has no voltage

[ogmoreboy]

I've decided to try using two modified fuses and some heavy wire to bridge between one of the empty fuse slots and 29. Wish me luck!

[ogmoreboy]

Bridge worked but still no horn! I now have 12 volts to the relay (relay has been tested and works fine) but no voltage at the steering wheel. Steering wheel horn switch works well - very low resistance on continuity test when pressed - and earth is good. Both horns blare when I put 12 volts across them and both earth wires from horns check out for continuity.
I am now going to look for loom connector 44/5. Any ideas where that might be?

[ogmoreboy]

I made a bridge from another fuse - now have 12 volts to horn relay but still no effing supply to horn switch on steering wheel. Wiring diagram says it connects via to the loom via connector 44/5 which I think is behind the dash. Does anyone know where I can find the thing or how to remove the dash?

[Clan]

Originally Posted by ogmoreboy

I made a bridge from another fuse - now have 12 volts to horn relay but still no effing supply to horn switch on steering wheel. Wiring diagram says it connects via to the loom via connector 44/5 which I think is behind the dash. Does anyone know where I can find the thing or how to remove the dash?

try earthing the wire which goes to the horn switch , before before it gets to the horn switch on the column , earth it somewhere solid like the actual body rather than the column see if it works .

[ogmoreboy]

Thanks Clan. I tried earthing it to the cigarette lighter earth - no voltage (or rather about half a milliamp) so I took the wheel off and removed the plug from the socket (44/5?) that feeds the clever little doohickey that lets you turn the wheel without twisting the horn and airbag cables. No voltage in the black and green cable, which should be the live feed from the relay. Ho hum. . .
I also measured the four contacts in and out of the doohickey for continuity - only one seems to be connected!
I think I might give up and build my own horn circuit - I'll stand back when I plug it in just in case I've managed to wire it to the airbag circuit!
I'm still open to less radical options. . .

[Clan]

Originally Posted by ogmoreboy

Thanks Clan. I tried earthing it to the cigarette lighter earth - no voltage (or rather about half a milliamp) so I took the wheel off and removed the plug from the socket (44/5?) that feeds the clever little doohickey that lets you turn the wheel without twisting the horn and airbag cables. No voltage in the black and green cable, which should be the live feed from the relay. Ho hum. . .
I also measured the four contacts in and out of the doohickey for continuity - only one seems to be connected!
I think I might give up and build my own horn circuit - I'll stand back when I plug it in just in case I've managed to wire it to the airbag circuit!
I'm still open to less radical options. . .

so what happens when you earth out that black/green cable at the relay? the horn should sound ...

[ogmoreboy]

I'll give the black green wire earthing a go tomorrow.
I am still confused by the lack of continuity in the SRS contact reel (I found out what they call the doohickey) - if there is max resistance between 4 of the five connections, I can't see how the horn switch or the airbags can work.
However I still need to find a way of getting power to the steering wheel for the horn.

[KBB]

I think you are referring to the contact reel. Be aware that they often place in the connector safety shorting bars so when people disconnect it and start probing with meter leads and power probes the terminals are shorted together to prevent an ohm reading being taken of the airbag which can initiate them.

[skyship007]

Originally Posted by ogmoreboy

Thanks Clan. I tried earthing it to the cigarette lighter earth - no voltage (or rather about half a milliamp) so I took the wheel off and removed the plug from the socket (44/5?) that feeds the clever little doohickey that lets you turn the wheel without twisting the horn and airbag cables. No voltage in the black and green cable, which should be the live feed from the relay. Ho hum. . .
I also measured the four contacts in and out of the doohickey for continuity - only one seems to be connected!
I think I might give up and build my own horn circuit - I'll stand back when I plug it in just in case I've managed to wire it to the airbag circuit!
I'm still open to less radical options. . .

You might want to park in front of the A&E at your local hospital, or remove the steering wheel using real Volvo service data.
A current clamp can save a lot of time fault finding.

[ogmoreboy]

Originally Posted by KBB

I think you are referring to the contact reel. Be aware that they often place in the connector safety shorting bars so when people disconnect it and start probing with meter leads and power probes the terminals are shorted together to prevent an ohm reading being taken of the airbag which can initiate them.

I can see why this sort of safety device might be included in the connector, and if it has, and is triggered at very low current levels, I have messed up.

There is evidence of damage to the reel itself. It rattled and when I examined it there was a piece of the casing snapped off where the ribbon cable attaches to the horn-side connector leaving a jagged edge. The ribbon cable appears to be damaged at this point.

Whatever the case I am going to get a replacement.