Horn relay?

[keith1948]

Hi Roger

Rob in his post above beat me to how your particular SB40 relay is wired up.

There is a wiring diagram in this link to the Jowett Javelin which uses the SB40. Scroll down to item 22 and you will find it.

https://jowett.net/Parts/TechNotes-Part24-ServBul.htm

Hope it works now

Also thanks to Richard who posted a photo of the Lucas horn relay 33188. These were also used on a lot of late 1950's early 1960's British cars as well as the TR4A. Mine is not a Lucas relay but a R246 which I think was made by Clear Hooters of Bedworth but it is wired the same.

I guess we are all now world experts on these relays. I have certainly learnt a lot more about the different types and their variations from these posts. 

Keith

[rogerowen]

12 hours ago, RobH said:

 Those labels are just a general generic  indication  - not specific to your application, it's just a drawing I found of the SB40 relay so ignore the words. As for other Lucas relays it comes in different styles.

 According to the wiring diagram for the '4A,  W1 goes to earth via the horn button.  Power comes from the battery via a fuse to C2 and there must be an internal connection in the relay between C2 and what would be W2 so that the volts go both to the contact and one end of the relay coil. Apparently with your version of the relay there is no earth connection so apologies for any confusion. 

It also means my earlier post re connections for a modern relay needs amendment.  86=W2 should be linked to 87=C2  and there is no earth connection. 

 

Thanks RobH, There's no relay in my manual (maybe because my car was a USA export),  

[Tr4aJim]

RogerO, I believe the shop manual only shows the TR4 wiring, not the TR4A (the manual is a bit light on other 4A details as well). 

The Autowire diagram for the 4A does show the horn relay (see attached).

FYI - The Autowire diagram has some errors unfortunately (i.e. the “flash to pass” lighting switch wiring is incorrect). I have attached a (crudely) hand drawn diagram of how my lighting switch is wired. Other 4A owners here in the US have confirmed the same findings.

Jim

 

Edited August 6, 2019 by Tr4aJim

[keith1948]

Hello again Roger and Jim

The 4/4A workshop manual does not have the wiring for the 4A as you correctly state. The Autowire diagram is not entirely correct either. What you need is the wiring diagram in the small Triumph TR4A Owners Handbook. This seems to be the only correct version I have found.

On terminal A1 of the control box (the terminal at the top) there are 2 thick wires connected coloured brown/blue. One of these goes to the ignition switch and the other goes to an in-line fuse near the horn relay. (Autosparks has this wire as brown/yellow but it is definitely brown/blue). From the fuse the next bit of wire is purple to C2 of the relay. From C1 there is a purple/yellow wire to both horns. From W1 there is a purple/black wire to the horn push on the steering wheel. Both horns are also linked by a black wire that is earthed next to the offside horn.

If wiring any other accessories on the car then it is best to use colour coded wires so you know what the wires go to. Nothing worse than trying to sort out a bunch of red or green wires installed by a previous owner.

My 4A was ex-USA as well but the wiring in the handbook seems to be the same. Mine also had large clear plastic lenses on the front indicators that I changed to amber coloured glass ones.

Keith

 

[rogerowen]

2 hours ago, keith1948 said:

Hello again Roger and Jim

The 4/4A workshop manual does not have the wiring for the 4A as you correctly state. The Autowire diagram is not entirely correct either. What you need is the wiring diagram in the small Triumph TR4A Owners Handbook. This seems to be the only correct version I have found.

On terminal A1 of the control box (the terminal at the top) there are 2 thick wires connected coloured brown/blue. One of these goes to the ignition switch and the other goes to an in-line fuse near the horn relay. (Autosparks has this wire as brown/yellow but it is definitely brown/blue). From the fuse the next bit of wire is purple to C2 of the relay. From C1 there is a purple/yellow wire to both horns. From W1 there is a purple/black wire to the horn push on the steering wheel. Both horns are also linked by a black wire that is earthed next to the offside horn.

If wiring any other accessories on the car then it is best to use colour coded wires so you know what the wires go to. Nothing worse than trying to sort out a bunch of red or green wires installed by a previous owner.

My 4A was ex-USA as well but the wiring in the handbook seems to be the same. Mine also had large clear plastic lenses on the front indicators that I changed to amber coloured glass ones.

Keith

 

Thanks Keith, this is useful. I've found the purple wire and got 12 volts each side of the in-line fuse and at C2.  Now chasing the earth connections.

[tthomson]

On my late TR4A, the relay is 6RA, but has four terminals, C1, C2, W1, W2. The loom supports this configuration by having two purple wires supplying the relay,  a purple and black wire to the horn push, and a purple and yellow wire to the horns.

Lucas documentation states that  terminal W2 is the start of the winding and should be connected to +ve and that W1 is the end of the winding and should be connected to -ve.

Therefore on a negative earth car, W2 is connected to the thinner purple wire, and W2 to the purple and black wire. C1 and C2 are not specific so one of them connects to the thick purple wire and the other to the purple and yellow wire, whichever is easier to do.

(NB. Purple wire is fused supply direct from the battery without going through the ignition switch)

For a three terminal relay there is no ground connection. C1 and C2 remain as in the four terminal version, W1 is the connection to the horn push, but W2 is not brought out to a terminal it is connected to C2 internally.

I am pretty sure the earlier 3 terminal relays work in the same way

If the coil was automatically grounded through the frame, the relay would always remain engaged due to the permanent supply from the battery.

 

Kind regards

TT

[rogerowen]

Thanks TT, I'm chasing systematically (cleaning stuff as I go), pretty sure at this stage my problem might be the wiring to the horn push - there's a rather messy looking coil of wire running up the steering column.

[RobH]

Just a thought- -If you get as far as the horn push itself with the wiring checking out OK, some people in the past have had trouble with the contact brush inside the horn push assembly.

Item 80 here :https://rimmerbros.com/Item--i-GRID200600 

[rogerowen]

54 minutes ago, RobH said:

Just a thought- -If you get as far as the horn push itself with the wiring checking out OK, some people in the past have had trouble with the contact brush inside the horn push assembly.

Item 80 here :https://rimmerbros.com/Item--i-GRID200600 

Hmm, I've got continuity from the top of the brush right through to the earth of the horns - but only 9.5 volts across brush top and earthing point on the inside of the steering wheel. Electrics are not my strong point!

[rogerowen]

5 hours ago, Tr4aJim said:

RogerO, I believe the shop manual only shows the TR4 wiring, not the TR4A (the manual is a bit light on other 4A details as well). 

The Autowire diagram for the 4A does show the horn relay (see attached).

FYI - The Autowire diagram has some errors unfortunately (i.e. the “flash to pass” lighting switch wiring is incorrect). I have attached a (crudely) hand drawn diagram of how my lighting switch is wired. Other 4A owners here in the US have confirmed the same findings.

Jim

 

This is useful, thanks Jim.

[RobH]

Can I suggest that you try a link wire direct from W1 on the relay to earth? That should pull in the relay (and perhaps sound the horns).  If the relay pulls in with the link but does not when you press the horn button, it confirms a poor connection to the latter (since you say you have confirmed the push does make a good earth).

The 9.5 volts you measure could be because of the series resistance of the relay coil or it could be a poor connection between W1 and the horn push. It rather depends on the type of  meter you are using.

[rogerowen]

17 minutes ago, RobH said:

Can I suggest that you try a link wire direct from W1 on the relay to earth? That should pull in the relay (and perhaps sound the horns).  If the relay pulls in with the link but does not when you press the horn button, it confirms a poor connection to the latter (since you say you have confirmed the push does make a good earth).

The 9.5 volts you measure could be because of the series resistance of the relay coil or it could be a poor connection between W1 and the horn push. It rather depends on the type of  meter you are using.

Brilliant, that got the horn working (it also set off the Moss security alarm - so I've disabled that). There is no continuity between the horn button contacts when button is pushed.

[RobH]

People have had trouble with horn pushes before and one fault has been a lack of continuity through the steering column to earth, because of the adjustment clamp not being tight. This topic explains it; might be worth a look?:

https://www.tr-register.co.uk/forums/index.php?/topic/37267-horn-woes/

 

[rogerowen]

1 hour ago, RobH said:

People have had trouble with horn pushes before and one fault has been a lack of continuity through the steering column to earth, because of the adjustment clamp not being tight. This topic explains it; might be worth a look?:

https://www.tr-register.co.uk/forums/index.php?/topic/37267-horn-woes/

 

Hi Rob, yes this could be the problem area. I'm suddenly reminded of my first TR2 back in the late '60's - it had the same problem. I fitted a spring loaded 'flick switch' to the dashboard and added a 'Dymo' label saying 'Hooter'. Still managed to press the inoperative horn button when I needed to toot though!

[tthomson]

Hi Roger,

Depending on the steering wheel, you should be able to remove the horn press by levering it off. Once this is done, you should see a brass track that the "pencil" connects to, and the horn press should have spring loop that connects to the steering column. Using a temporary connection between the brass track and steering column should sound the horn.

If it does not, then there is an earthing problem somewhere along the steering column.

The steering column of a TR4A has braided links that cross the rubber linkages, and to the chassis at the rack end. and if one of these is broken, the horn will not sound.

If the horn does sound when the temporary wire is connected, then the horn press , "pencil", or the loom to the horn press has a fault. (the spring loop on the horn press may also be corroded and/or not making good contact with the column).

Kind regards

TT

[rogerowen]

Thanks TT, still a bit confused though. I've got continuity from the brush connector to the bottom of the steering column  (someone has run a wire down held on with insulating tape)! Bridging between the top of the pencil to the inside of the steering wheel does nothing - should this be earth? I can find no continuity between the steering wheel and body earth. Also there is no continuity between brass and copper wire of the horn push when it's pushed.

[RobH]

Yes the steering column needs to be earthed for the thing to work and the steering wheel boss should be earthed because it is clamped to the column.  Sounds like a previous owner has tried to fix a bad connection with that extra wire.

If you bridge between the top of the pencil and a real earth does the horn sound? If not is the pencil touching the slip-ring? Is there continuity through the pencil? 

 

Here are some pictures from someone else who had similar problems (but with an after-market steering wheel)

https://tr4triumph.blogspot.com/2010/06/making-standard-horn-work.html

Edited August 7, 2019 by RobH

[rogerowen]

Thanks RobH, I cannot see an earth connection to the steering rack - will have a look in the morning  (neighbours)!

[RobH]

There isn't a connection as such Roger, it just comes by all of the metalwork being bolted together and to the chassis. Corrosion or paint can prevent that.  As the last link shows there should be a jump-wire across the joints in the column.

[rogerowen]

Thanks Rob, In this picture from that link you sent me there looks like a wire going to the steering rack grease point, not sure if my car has that. I will try to feed a temporary earth to the steering wheel and see if that works.

[keith1948]

Good morning Roger again

Just had a look at the horn wiring on my USA import TR4A that still has the original wiring. Tracing back from the relay - terminal W1 - there is a purple/black wire. On my car this goes into the wiring loom near the relay and emerges from the loom where the steering column used to be on the left side under the dashboard. Then the DPO (dreaded previous owner) has connected a piece of brown wire to connect to the end of the purple/black wire that emerges under the steering column which is now on the right hand side. (note to me - I must change this to purple/black). The wire then travels up under the steering column in the channel with all the other wires to switches etc. and goes into the inside through a small hole (covered by the channel). If you remove the 2 small plastic covers (undo 2 screws) covering the base of the switches and you should be able to see the purple/black wire which is soldered to underside of the slip ring. If it has come unsoldered then you have to remove the steering wheel to resolder it. Then if you remove the horn push you will see the sprung 'pencil' that connects the slip ring via a wire to the underside of the horn push. The spring clips of the horn push then connect the circuit to the steering wheel boss when the horn is pushed. 

Now the inner part of the steering column (to which the steering boss is attached) is now the route to earth for the horn push. Triumph in their wisdom insulated the inside of the steering column from the outside by using PTFE or PTFE/rubber bushes between the inner and outer parts of the column. There is also a PTFE washer on the bulkhead side. There are also 2 rubber connectors lower down the column before you get to the steering rack that also has rubber mounting bushes. So it is vital that there are earth wires across the 2 rubber connectors (as others have said above) on the lower part of the column and also the earth wire shown in the last photo above to earth the rack. I somehow get the feeling that at a meeting at Triumph in the dim and distant past someone suddenly realised that the earthing of the horn push wasn't going to happen because of all the insulating connections, hence this bizarre system that looks very much like an afterthought. 

I have seen one car where another DPO connected a loop of copper wire wrapped around the column above the top rubber connector and then screwed this to the bulkhead. I am sure someone could come up with a better slip ring arrangement that would do the job better (might try one myself one day).

So there you have it. As Roger Hogarth and I discussed yesterday on the Colin Boother memorial run out to Welshpool, these postings must be the most comprehensive on the TR4A horn system and relays ever!

Hopefully you will have it sorted soon and can move onto the next gremlin.

Keith

 

[rogerowen]

Thanks Keith, Yes my DPO (probably a few back), has run wire wrapped around the column and held in place by insulating tape. I get continuity from the pencil brush top to the bottom of the column, but continuity gets lost from the top uj to the steering wheel. I've tried bridging between a known good earth and the column upper part - but no joy. Think my only answer is to strip out the column and clean all the joints and connections including new wire bridges on the uj's.

It's not the first time I've seen wire coiled around a steering column. I used to own a 1957 DKW 3=6 Sonderklasse which failed it's first MOT in my ownership on this point, as well as not having a screen washer. I discovered a workshop manual photograph to show the coiled wire arrangement was original at manufacture - and the slightly over-zealous MOT tester reluctantly passed the vehicle. Still not sure I needed to retrofit a screen washer - but hey!

One thought about the continuity readings I'm getting is that they could be weak and just not enough to pull in the relay. I'm sure I'll get there in the end....... then it's on to the wiper motor, and one side light + finding where the wires go for the rear overriders that had been removed at some stage.

Many thanks for all the input.

Cheers,

RogerO

[RobH]

Before doing drastic things like pulling everything apart Roger, it might be best to recap on what you have found.   If directly earthing the top part of the inner steering column doesn't help, there must still be a lack of continuity somewhere between the relay and the column. Perhaps the pencil isn't making proper contact or the horn push button itself ?  (The pencil is available in two lengths - so have you got the right type?)

 Once it works with a direct earth link on the upper column then you can sort out bridging the joints in the column.

Continuity is best tested with something that draws bit of current like a lamp or a buzzer, fed from a battery. 

[rogerowen]

4 hours ago, RobH said:

Before doing drastic things like pulling everything apart Roger, it might be best to recap on what you have found.   If directly earthing the top part of the inner steering column doesn't help, there must still be a lack of continuity somewhere between the relay and the column. Perhaps the pencil isn't making proper contact or the horn push button itself ?  (The pencil is available in two lengths - so have you got the right type?)

 Once it works with a direct earth link on the upper column then you can sort out bridging the joints in the column.

Continuity is best tested with something that draws bit of current like a lamp or a buzzer, fed from a battery. 

Thanks RobH, yes - will take it slowly, bit by bit.

Cheers,

Roger

[rogerowen]

Hoorah, cracked it. Was poor earth connection at the upper part of the steering column.