420 horns sounding intermittently

(Mac Booker) #1

I’ve got a problem with the horns sounding intermittently while driving my 420.
It’s almost certainly a ‘short’ somewhere completing the electrical circuit. It looks like I’ll have to take the steering column apart to get to the circuit / connections and that would appear to be a complicated and fiddly job.
Before I venture down this route, has anyone got any experience with this problem and any tips as to what to do and where to look please?
Thanks, Mac.

(Tigger) #2

Had this twice on a Mk2 - don’t know if set up is the same. The first was the sprung ‘button’ under central horn push had somehow been knocked to be at an angle and was occasionally shorting. The second event some years later was the steering column bushes - I didn’t tackle this myself but if I recall there are felt / plastic bushes top and bottom of the column which had failed leading to a short.

(The Jag Man) #3

This can be an arduous task. I spoke at length with a fellow lister and am still contemplating the job. Plan on at least a day and numerous beverages to complete this task. John Quilter in Oregon has done this with success. His skill level far exceeds mine!!

Loveland, Colorado

(John Quilter) #4

Gerard, Thanks for the vote of confidence. I think now after multiple times, column out, inspect and overhaul and still more fiddling and still more fidding (I have well moved up the learning curve on column work and know every tool I need to take out of my box and could write a PHd thesis on 3.8S columns). My initial issue was the horn would blow IF I moved the adjustable column down towards the dash. I initially THOUGHT that the wire in the inner column was likely frayed somewhere and unless taught would short against the inner column causing the relay to energize and the horn to blow. After inspecting the wire I found no problems with it. So while all apart I did fit new upper and lower bushings and lubricated them with some grease. Chamfer the edge before inserting to make fitting easier. For few drives the horn worked normally with the column adjusted in or out. Then it suddenly it would blow slightly even with the column pulled right out. I then took the plastic cover, horn button and horn ring off for inspection. It seemed to me that the tit with circlip and spring was not fully centered in the column and would sort of flop around sometimes shorting against the column. I then devised an improved method to keep it in the center when all was assembled. My fix was to take a dime sized fender washer, drill a dimple in it, and J B Weld it into the hat shaped contact on the underside of the horn ring thus creating a more positive locating arrangement for the tit. This apparently has worked given my two or three last drives in the car since. But along the way I found that the the position of the three nylon insulating nuts is critical. Also I had to shim the black cover out by the thickness of a very small thin washer on each mounting post that the screws that hold it in place attach to. Otherwise when fully tightened down the horn would start to blow (aargh). Tip: get new phillips screws that remove from the back of the steering wheel spokes that hold the black cover in place. Phillips screws in this location are MUCH easier to deal with than slotted ones and I had mine apart a bunch of times. So Tigger, from my experience I think your second sentence in your post is likely your issue. And along the way with so much horn testing and blowing I killed the last functioning horn so had to replace both as part of this job. And one final tip: If you take the column apart make sure the brass ring with the serrations is tightly crimped around the plastic insulator at the bottom of the column. If not, it will slip down (or up?) and and loose contact with the “finger” to which the bullet connector attaches to. Good luck to you. And do report back.

(tony) #5

The short-term solution is to fit a study button (usually on the bottom of the dash, near wheel, that activates the relay, so you will still have a useable horn, without unwanted honking

My 420G has been like this for much longer than my 20yrs of ownership.

Parts are missing from the steering column…and my spare steering column.

my '66 mkx wreck has a button as well, so not too hopeful that all its parts will be intact

(John Quilter) #6

Tony, A quick check of the SNJ Barratt website under Mark 10 shows a large number of replacement parts for the steering column and horn operating items are in fact available now. Not sure what your cars are missing but if you desire to return your car to factory stock the SNJ website (and perhaps other as well) are worth a look. I found most items that are likely to wear plus many others are shown.
John F. Quilter
Eugene, Oregon USA

(The Jag Man) #7

John, As inexpensive as flights are to Denver from Eugene right now, you should plan a ski trip, fix my steering column and we can video the entire procedure. Grand fun!

You can even stay here and save on hotels.


(tony) #8

I did completely overhaul the entire steering column recently, both columns had parts missing

Its pretty intimidating 1st time, but after a couple of strip downs, not scared anymore

I do have 2 further columns to pull apart, but they are still in cars.

must admit that I still am not 100% sure exactly how it works physically, so next time I will present pics of the areas that are missing, as the forum is much more picture friendly now

I know from the parts manual a little spring, tip, and retaining half-moons were missing

parts 41-43

(John Quilter) #9

Tony, Yes, a bit intimidating first time but as I said I’ve moved up the learning curve. The two #43 items are vital as they serve as insulators for the copper ring #44 and serve as a locator for the contact at the lower end of the wire #37, The power from the relay comes down from #46 what I call the “finger”. It rubs on the the ring which in turn connects to the lower contact on the wire #37.via a hole (not shown in the above drawing) in the inner column #16. This sends power up the wire to the “tit” at the upper end of the wire. The tit contacts the underside of the horn ring. When the horn ring is pulled (tilted) or the central button is pushed, it closes the circuit to the steering wheel and thus to the outer column and finally to chassis earth causing the relay to close sending high the amperage power to the horns. Just make sure the tit at the upper end of the wire under the horn ring can not flop around shorting against the inner column. I think the diagram of all this is a bit clearer in my factory parts manual for the S Type.

And Gerard, Thanks for the offer. I know there are non stops from Eugene to Denver but I know you can do this with patience, perseverance, and your knowledge.

(tony) #10

thx John, with yr expertise it should be easy for me next time

it was a good tip to get rid of the flat head screws for Phillips,

unless ur a contortionist, getting them out from behind the steering wheel gets stale pretty quick

might rile the originality buffs tho

are parts 43 plastic ?..makes sense, but I imagined them to be metal, like the top ones (part 31)

(John Quilter) #11

[quote=“awg, post:10, topic:372553”]
unless ur a contortionist, getting them out from behind the steering wheel gets stale pretty quick

might rile the originality buffs tho Any originality buff that wants to contort themselves enough to check this out can be my guest

are parts 43 plastic ?..makes sense, but I imagined them to be metal, like the top ones (part 31)
[/quote] Yes they are plastic or (nylon?) because they have to insulate part #44 from the column. Only the contact at the lower end of the wire contacts #44