Yes, it's possible to adjust the horns, and even possible to partly disassemble
and clean them (if they are the stock horns). However, first I'd be sure that
they are getting a reasonable proportion of the battery voltage applied to
them. The ammeter is not supposed to be in the circuit from the battery to the
horns, so it should not show a deflection if you blow the horns with the engine
stopped. With the engine running, it may show a deflection to the charge side,
as the generator puts back the power drawn by the horns.
It's best to remove the battery ground strap, as the wire into the horns is hot
at all times. You'll likely need to take the radiator braces loose from the
inner fender, then unbolt the horn. Remove the screw and the top cover. Now
is the time to connect a voltmeter across the two terminals and check the
voltage when you blow the horns. If you aren't getting at least 11 volts (with
the engine stopped), you need to look for the electrical problem(s).
One of the point contacts in the horn is threaded for the adjustment, with a
jam nut. To adjust the horn, connect a 30 amp analog ammeter in series with
the horn button. (The bullet connector near the horn is a good place.) Then
reconnect the battery, and blow the horn while watching the ammeter. The
target current is 8 amps. (Very early horns were 6 amps. I don't recall the
switchover date, but think it was early TR2.) If the current is too low,
loosen the jam nut and unscrew the contact 1 or 2 flats (decreasing the point
gap), then re-snug the jam nut and try again. If the current is too high,
screw the contact in (increasing the gap).
I've found that the push rod that operates the contacts is prone to corrode.
To get to it, remove the wires and take the horn to the bench. Carefully
remove the two nuts that hold the contact assembly together, noting the
position and order of each piece. Now, you can remove the push rod and clean
it and the hole it sits in. I used a thin film of silicone grease to lube
mine, it seems to have helped.
Randall
59 TR3A daily driver
On Thursday, August 31, 2000 1:29 PM, Crockett, Steve
[SMTP:steve.crockett@analog.com] wrote:
>
> Is is possible to adjust the horns on a TR3A? Right now all I get is a kind
> of low burbling sound when horn button is depressed. Ammeter shows current
> flowing....I used to get sound when engine was revving above 1500, but now
> it has diminished to barely audible.
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