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More beeping horn trouble

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tdskip

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So working on the conclusion that my horns in the TR6 were dead becuase they didn't make any noise at all when power and a good ground were connected I ordered a set of replacement horns.

Went to check them with a good power source and good ground and nothing - which wasn't waht I was expecting.

Shouldn't they beep when confronted with power and an earth circut? I know power if getting through them since the test lamp lights up that I'm using to complete the circuit....
 
Might the test lamp be drawing too much power from the horns? (<--mind you, this is a wild guess from one who doesn't understand electronics all that well )
 
What are you using to supply power for the horns? I would hope it is an automobile battery so you have enough amperage to make the horn elements vibrate. If not using battery, the test lamp would illuminate, indicating voltage, but there may not be enough amperage from the power supply to make the horns sound. I'm just guessing since I don't know how you are supplying power to the horns.
 
Hi guys - thanks for the ideas. Let me check without a test light in the circut. I am using the battery (charged and healthy) as the power source.
 
Did you hook both contacts to the battery?
 
Hi Don, I did. I tried both ground to frame and ground back to the battery.

Seems unlikely that I got two new bum horns?
 
Dead battery? It don't take that much juice to beep those horns.
 
They do draw a lot of current normally - I think it is the test light adding too much resistance.

Randy
 
I agree, can't use a test light to complete the circuit.

Horns are strange, they draw current intermittantly. The peak current has to be quite high for them to function at all, but the average current is much lower.

Basically when power first hits the horn, the coil must pull both the sound diaphragm and the contacts far enough to open the contacts. If the current is limited, the coil isn't strong enough to pull that far and the contacts never open. With the contacts always closed, the diaphragm doesn't move any more and the horn doesn't make any sound.

So a poor connection or corroded wire or marginal relay contact can keep a 'good' horn from working at all, even though it appears to be getting voltage.
 
Once again, thanks guys. Testing it directly with the wires connected to the battery did the trick.

Now I need to go back and test the existing ones with direct to the battery wiring to see is they are in fact good.
 
I thought that's what you had done?
How did you try it?
 
Shorter leads this time - no change in the battery condition - but connected directly to both the battery posts rather than one to a chassis ground.


Evidentally that did the trick.

Wonder if that same test approach will get the old/original ones to work?
 
I would suggest you clean up the contact area between the horns and where they bolt onto the metal. It sounds like a high resistance ground there when you had negative from battery hooked to the chassis.
 
TR6 horns (like most car horns) don't ground through the mounting, which is why they have two wires.
 
Randall is correct about the horns. The schematic shows they isolated the TR6 horns from chassis ground. I should have looked before I wrote. (Spitfire horns are using chassis ground on mine) I'd check the horn button assembly in the steering column. May be bad contact plate or broken wire.
What do you think, Randall?

John
 
Keyspit said:
What do you think, Randall?
Click to expand...
Not enough information to make a guess. Maybe the car wiring is fine, and he just decided to test them on the bench? I've even lost track of what year TR6, so don't know if it has a horn relay or not.

But the two most common problems seem to be either someone leaving the ground wire off the steering rack; or the jumper wire across the rubber joint in the steering column. I'd take a quick look at those first; then do a little troubleshooting (maybe even try supplying a ground to the upper steering column); before pulling the horn button apart.
 
Hi guys - I did bench test the new ones. Focused on the seat frames today, so no more testing/troubleshooting on the '74 TR6 horns.

Thanks for checking in though!
 
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