TR4/4A 67 TR4A Horn problem

[JDstr4a]

Went through the search results and read a lot about these horns, but still have a couple of questions.
The horn will work when pushed really hard or I push the steering wheel at the same time.
Checked the brush continuity ok and the tab to side contact when button pressed.
I took out the signal and headlamp switches but couldn't see anything suspect or much of anything at all.

I noticed the side contact is only connected on one end, is this correct?
I'm not sure where to start checking for a pinched or broken wire,is there some other ground jumper or feed path I should be checking?

Thanks
JD

 

[KVH]

I have fixed the horns on both of my 4As. Each time I needed a refresher course. But each time it was a bad connection, not a totally broken wire.

A bad relay was my last problem. I took it apart very carefully, and cleaned the contacts, and now my horn is perfect. The prior posts from TR3Driver explain how to test the relay. Basically, you bypass the steering wheel and horn push, and attach a direct negative feed to the relay and see if the horn works. I just used a fine file to remove corrosion on the contacts.

Another time it was that purple wire coming up the steering tube. It was frayed at the brass contact plate, and about ready to break. A very poor and unreliable connection.

A third time my steering shaft was not grounded. That was easy.

Each time I hunted down all the other wires and connections, and found myself wasting time. That vision of some wire just severed and hanging never seems to come true.

Good luck. (watch, you'll find a wire!)

 

[sail]

each time it was a bad connection, not a totally broken wire.

My horns never worked. Inline fuse looked good, replaced it. Tested everything. Kept yelling at other drivers. Finally tested the fuse. Haven't yelled since.
The horn button ends up purple/black at the relay by the right horn. I would start there but it's probably a fuse.

 

[Rrbbeerrttoo]

Keep looking. If it works when pushing ,whatever, in the steering area, the problem is not the fuse. Must be a loose wire ( ground, of course ) someplace near the steering or steering shaft. The purple/bk? wire connected to the slip ring could be the problem ( this wire passes thru the steering column ). The connection to the slip ring is not readily visible; it is under the bakelight which supports the slip ring. It is a simple job to look although you have to bend the tabs to remove.

Your luck...this was my problem today. Your post motivated me to inquire why my horn was not working for ten years...so thank You.

 

[SpannerMan]

I'm not sure where to start checking for a pinched or broken wire,is there some other ground jumper or feed path I should be checking?

Thanks
JD

If I remember correctly the wire for the horn button comes from the ground side of the 'control' circuit of the horn relay and up to the slip ring in the column, which is isolated from the outer column. (One problem that happens is if the bushings wear or something is loose, the horn can sound unintentionally when the slip ring grounds to the outer column). When you press the horn button, the brush contacts the slip ring, and the ground path is then through the button and down through the inner (moving) part of the column, across the 'donut' on the engine side of the firewall, and to the body ground via that ground strap tied to the steering rack at the bottom end of the column.

You can isolate an open circuit in the latter part of the ground path by checking for continuity between the upper, inner steering column to the negative battery terminal. Use your multimeter set to resistance, for instance. If it is 'open' (infinite resistance) then you should establish why. You could alternatively try jumping to the negative terminal and trying the horn. The first way is a bit safer although the second way should be fine unless something is wired up very wrongly.

This is on a TR6 but I believe it would be the same as TR4A. Also, I am working from memory so I might not be 100% accurate on the setup inside the column without looking at it again but it shouldn't affect the main point. You should be able to narrow it down somewhat this way.

 

[Rrbbeerrttoo]

When trouble shooting one must consider all possibilities as all good recomendations are good, however,
in my Tr4a the slip ring under the horn button on the steering can not contact ground as it is solidly attached to the bakelite mounting ( plastic ) at three points, so there is no way it can dislodge. The bakelike mounting is a full circle piece fitting/locked right into the steering metal case where the signal sw. also mounts. Also, the slip ring has at least 1/4 inch clearance all around from the steering center column where, yes, it could be grounded. Ummmmh, but OP would have noticed the column slop if the bushing were the reason.
A continuity check as previously recomended may be the best way to locate the intermitent open circuit, but I also suggest checking the wire connection to the slip ring, as it was in my car.
Good hunting!

 

[JDstr4a]

Thanks to all for your suggestions! I put a new battery in the meter and am going to have at it!

 

[JDstr4a]

Took another look at this last night. Pulled the light switch and turn signal and was able to see the slip ring and the wire seemed attached well although the insulation was pulled back. Also checked the ground strap on the steering coupling ok. I have a new horn push contact from Moss so I think I'll cut it to a proper length and try to get continuity verified from the slip ring wire to variuos ground points on the steering assembley with the button depressed. Wish me luck!
JD

 

[JDstr4a]

Being the impaitent type, I had at it again with the meter even with the battery still out. It seems the pb wire was almost a dead short to ground so I disconnected it at the relay. Then tested from pb on the slip ring to the brush good and from the pb to ground with the button pushed though it seemed a little inconsistent. I was able to get my finger in there and grab the terminal where the wire is attached and was able to wiggle it a little. I felt around for the tabs and found three at about 12 4 and 8 oclock respectively. the whole thing seemed a little loose for fore and aft motion. The 4 oclock tab was bent almost flat twords the steering wheel and the other two were twords the firewall much more. I cant really see how they work so does anyone know which way they should be bent?

 

[Rrbbeerrttoo]

Yes, the slip ring and its plastic mounting are a bit loose, do not to be absolutely tight, so long as they do not rotate. The mounting plastic is locked into the column. The only purpose of the three tabs on the slip ring are to mount the slip ring to the plastic piece. With a proper tool I was able to bend the tabs below the plastic mounting. Do not worry about it as the tabs cannot reach grounding point. The fourth tab ( at 6'0c )has the wire from the relay connected to it, as it should be!

Hate to give advise when I am also having a horn problem. I took apart the full steering column and staill cannot solve my problem, same as I did twenty years ago.

Robert
1966 Tr4a irs

 

[JDstr4a]

Thanks for the reply, I'm going to leave the tabs and proceed with the contact brush replacement today. Good luck with your adventure!
JD

 

[JDstr4a]

Well, only three years later, I finally got around to attacking my horn problem. Started at the steering rack ground, and after much scratching and cleaning, found the "earthing cable" in the upper coupling flopping around. I guess pushing the steering wheel would make contact and get an intermittent beep! Surprised you didn't hear my yahoo! Now keeping my fingers crossed while I repair the connection and reinstall the relay, fuse, etc. I like simple :highly_amused:

 

[Geo Hahn]

Well, only three years later...

Glad it was something simple... only three years.

 

[JDstr4a]

I have honk! just nice to check off one more challenge and hopefully I wont have to yell and or gesture as much! Now back to the carbs.

 

[glemon]

Don't sell yourself short, it has only been 2 years and 10 months since your adventure started. There are many weak links in the chain needed to make the horn work on the TR4-6. They are a PITA of the first order, and I am not sure which is the bigger problem, the tendency not to work when you want them to, or the tendency to work when you don't want them to. Most all of the weak links have been identified in this topic. Unfortunately, there are so many weak links that it is often a multiple problem making it harder to diagnose and fix. In addition, I had a steering wheel squeak or rub, loud enough to be irritating every time I turned the wheel, I thought it would go away when I put new steering column bushes in, but it turned out to be the little tubular contact piece rubbing against the contact ring, some grease fixed the squeak and I think it helped my horn reliability as well.

 

[JDstr4a]

Thanks for the support, after reconnecting the earthing strap, I still was not getting a good ground till I gave it a shot of CLR to improve the connection. I have the squeak too, but that's another day.

 

[dklawson]

I didn't see this thread when it started or I would have suggested the ground wire through/around the shaft coupling. I have had that fail on our GT6. When the car still required annual inspections I tried several workarounds to get the horn to work... each attempt was temporary at best. Eventually I took the joint apart and made a new braided lead to replace the failed one.

I'm glad you got your horn working again !

 

[carpecursusII]

As long as this thread is alive again, has anyone used the new horn relays that moss is selling? They are a black cylinder and bare no markings of C1 C2 W1 W2, they only have some numbers next to the contacts. Any ideas on how to wire these up?

 

[dklawson]

What numbers are on the Moss relay terminals? Might they correspond to the numbers used on the more common, modern Bosch/ISO cube relays?

 

[Geo Hahn]

...they only have some numbers next to the contacts. Any ideas on how to wire these up?

Staring at these two schematics may make it apparent:

Though on the Bosch relay I think the terminal shown as 'G' in that drawing may be labeled '87' on the relay.