Topic: Rim Blow

[Brian Conway]

     Have a Rim Blow that doesn't honk any more.  Took a look today and after fiddeling around with the circuit tester ascertained that I have power at all 4 phillips  head screw locations.  I have power at the 2 soldered connections to the copper strip.  I have power on the copper strip at the right side but not on the left side.  By my count that is 8 test locations.  By turning a connection screw the horn will be in constant honk mode. Test results remain the same.  All 7 locations have power except the surface of the copper strip on the left.  So would it be reasonable to conclude that the Rim Blow switch is defunct ?  Thanks for the help.  Brian

[J_Speegle]

Sounds alike a two ended break so yes. Be very careful with these - had a friend who's car burnt to the ground and they always suspected a short in the wheel since the horns were blazing along with the car    Might have just been another reason and those wires just happened to biurn like everything else but in a close position at one point

[rayms69]

my horn continuously honks, I just unplugged the horn connector. Does this mean someone probably squeezed it too hard at some point? I don't believe it has ever been removed, my interior was untouched inside other than normal wear and tear that 30K miles would do. Can it be fixed by separating the copper strips?

[69cobrajetrugae2]

Pull the wheel and connect the copper posts.  If the horn honks the problem is in the wheel.

The copper posts connect to the inner and outer steel rings under the wheel.  When the wheel is turned you may hear a light squeal.  That noise is very bad.  The lubrication is gone between the posts and the steel rings.

The copper posts are nestled inside a plastic carrier as part of the turn switch assembly. When the lubrication is gone and the wheel is turning there is undue stress on the posts and the plastic carrier which can cause the carrier to break. When it breaks it could cause a short which could burn your car to the ground, as in the case of Jeff's friend.  I don't know if the turn signal switch is fused or un fused.

If it is fused and the turn signal assembly is damaged, it is possible for current to flow to ground and create heat but not blow the fuse.  After market turn signal switches may be weak as compared to the Fo Mo Co OEM part. If your turn signal is on, and the horn honks, there is quite a bit of current flow through the turn signal switch.  I do that sometimes by accident when turning a corner.

I used Lucas engine assembly lube on the steel rings.  I rubbed it all around the steel ring for complete coverage but was careful not to use to much.  Just coat it.

Brian.  With the wheel off connect a VOM set to continuity with the buzzer on.  Starting at the steel rings gently flex the wheel or otherwise disturb the connections before the wires enter the switch.  There may be something loose or cracked where the steel rings attach to the wheel or where the switch wires attach.

If you need a switch get the Daniel carpenter. It comes in a white box. The other ones are junk I hear.  I checked mine in the store before I bought it with a VOM and clips.  I gently depressed the new switch every inch and listened for the beeper.  It was good.

When I was installing the switch in the wheel I had my VOM connected to the switch. About half way through the buzzer went off.  OH NO, I TRASHED THE NEW SWITCH! 130 BUCKS OUT THE DOOR!  I maneuvered the switch and got the beeper to go off.  I must have put a small bind in it.  It has been working great, been about 6 months.

Remember, the switch cannot burn your car to the ground.  The turn signal assembly can.

Hope this helps.

[J_Speegle]

Remember, the switch cannot burn your car to the ground.  The turn signal assembly can.

Don't know if I would agree - but its opinions until we try it on a car with the camera running

Great advice on the switch and replacement

[69cobrajetrugae2]

Jeff.

You are right and after thinking about it, I am wrong.  A faulty rim blow horn switch could cause a fire.

If the switch stuck on and the horns blared for hours unnoticed then there might be a fire. The turn signal assembly would be routing the current to the horns hour after hour.  My guess would be that Ford engineers did not design the horn signal assembly for this service duty.  It could also be the reason Ford and other auto manufactures discontinued the rim blow horn design after a few years.

If the horns drained the battery the question would be how much, if any, damage would there be to the turn signal assembly.  One could set up test equipment and measure the effect this would have, temperature, current loads and so forth and resulting damage to the horn switch, if any.

Did Ford design the turn signal assembly to handle this extended load? 

Did ford design the light switch to handle extended loads if the lights we're left on?  They probably did, who hasn't done that?

What if the brake light switch stuck?

Therefore if the horn switch failed and the horn was stuck on for hours then a fire is not outside the realm of possibility.

I think I will disconnect the battery to be on the safe side when the car is not in use.

Thanks Jeff.

[J_Speegle]

Sounds like allot of work

Things can easily go wrong and simple drain the battery if the fault keeps the flow below the treashold of the of the fusible link built into the wiring at the connection point to the start relay. Above that the link should burn before the wiring goes up in flames   Been there done that one

But if Murphy's law kicks in it can get ugly in my experience

Professional Firefighter in a decent size metro fire department for over 30 years

[midlife]

Sounds like allot of work

Things can easily go wrong and simple drain the battery if the fault keeps the flow below the treashold of the of the fusible link built into the wiring at the connection point to the start relay. Above that the link should burn before the wiring goes up in flames   Been there done that one

But if Murphy's law kicks in it can get ugly in my experience

Professional Firefighter in a decent size metro fire department for over 30 years

Not all 69/70's had fusible links at the starter solenoid.  The problem with fires being started in these old cars are when any non-fused signal is inadvertently shorted to ground.  The ammeter lines come to mind.  The horn gets its power in 69 from the headlight switch; in 70 from a fuse in the fuse box.  Rear brake lights all come from the headlight switch through the brake switch up to the turn signal switch.  The back side of the turn signal switch has rivet heads that if you are not careful (particularly with repros!---ask me how I know!) they can ground to the steering hub, which is chassis ground.  I don't believe the power to the brake lights are controlled by the headlight circuit breaker.

[69cobrajetrugae2]

Mr. midlife.

The copper posts in the turn signal assembly that switches the horn gets it power from the headlight switch in a 69?

 Is that circuit fused or unfused?

If the rivets in repop turn signal assembly short to the steering wheel hub, and if the circuit is unfused, then there would be a whole lot of smoking going on!

 

[midlife]

Mr. midlife.

The copper posts in the turn signal assembly that switches the horn gets it power from the headlight switch in a 69? Yes one side is always hot.

 Is that circuit fused or unfused?  Neither: it may be protected by the circuit breaker in the headlight switch.

If the rivets in repop turn signal assembly short to the steering wheel hub, and if the circuit is unfused, then there would be a whole lot of smoking going on!  It happened to me, but no smoke.  I basically shorted out the turn signal switch to the point that I had to replace it.

[69cobrajetrugae2]

Mr. Midlife.

Why are there fused and unfused circuits in a car?  I have always wondered about that.

[rayms69]

uh? I know if I connect my jumper wire, the horns go to beeping. So I hoped I could find where maybe someone mashed it at one time. I got side tracked with brakes, stripped out the brake warning switch, so ordered NOS replacement and turn signal switch NOS, maybe my fuse popping on turn signal actuation will go away. An easy fix for the horns would be nice.

[midlife]

Mr. Midlife.

Why are there fused and unfused circuits in a car?  I have always wondered about that.

Beats me.  I presume Ford determined that the ammeter should work 100% of the time; if a fuse was blown, the meter would never read and who would notice that?  The brake lights and horn are also not fused, presumably due to safety concerns. 

And please don't call me Mr. Midlife---Mid will do.  We're informal here.