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Overdrive - relay switch


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I need a new relay switch for my 1967 4A. The current one isn't that old but is playing up (it has a mind of it's own) - so I am wondering if it's the right one.

 

I thought a relay was a relay!

 

Do I need to get particular switch?

 

Tips please?

 

Phil

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Hello Phil,

 

I had the same problem, intermittent connection, and then it started working on its own, the wire insulation had worn through and it was earthing somewhere, found out the hard way, smoking wire!! I think the wires take a bit of a tortuous route from the o/d relay to the connectors and if the lead is poor or grommets missing it can cause problems,

 

Good luck, Andrew

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Correct relay for overdrive is the Lucas 6RA and they do last the course. They turn up fairly often on fleabay and at autojumbles. If its the stalk switch then you are also better off getting an old stock original as the repros arent the best and do have a habit of the stalk coming off in your hand! Care must be taken with getting the wires to lay correctly down the column clip on tray as they are easily "pinched" causing all sorts of problems.

Stuart.

Edited by stuart
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Correct relay for overdrive is the Lucas 6RA and they do last the course. They turn up fairly often on fleabay and at autojumbles. If its the stalk switch then you are also better off getting an old stock original

 

 

Phil & Stuart,

The Lucas 6RA is a whole family of relays, some are designed for continuous use (like overdrive actuation), some for intermittent (Horns), some have Normally Open or Normally closed contacts (or both) plus there are different mounting brackets. Part Nos are SRB111, SRB146, SRB301, SRB113, SRB201, SRB131, SRB220, SRB143, SRB230 --- they are *all* marked 6RA and you can often make a different 'flavour' 6RA work in your application.

However, do take care of this intermittent vs continuous thing - these types have diferent coil resistances and the intermittent type will overheat in a continuous application [Don't use a horn relay for the overdrive].

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The new repro relays are useless. I don't know about the new Lucas ones, but the only ones I use now are either NOS original Lucas ones or used Lucas originals. I went through three defective repros before concluding this. If the relay fails open (mine did) then you can fry your overdrive by backing up.

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  • 2 weeks later...

Hi Fellahs

 

many thanks for the information, as always very useful. Dave, re-your upload about the part nos. Is there a surefire way of selecting the right on?

 

Can I rely on the supplier to know which is the most appropriate?

 

I don't want to risk putting in the wrong part!

 

Ta

 

Phil :-)

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Hi Phil,

 

The original overdrive relay for your car is Lucas - model 6RA - part number 33213.

 

This was fitted to all overdrive equiped TR4's through to the TR6.

 

Easy to identify as all the Lucas relays are clearly stamped on the metal casing with the model, part number, week and year of manufacture.

 

Also they should have four Lucar connectors marked : C1 : C2 : W1 : W2

 

I cannot find any photos of an overdrive relay.

 

However you can get the idea from the following photos of a 6RA relay for the horn circuit on a TR4A.

 

Regards, Richard

 

XX010.jpg

 

XX011.jpg

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Hi Phil,

a 33213 (old numbering system) is an SRB111(new int'l catalogue)

available here:

http://www.autoelectricsupplies.co.uk/product_list/113

 

dave

 

many thanks for the information, as always very useful. Dave, re-your upload about the part nos. Is there a surefire way of selecting the right on?

 

Can I rely on the supplier to know which is the most appropriate?

 

 

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  • 4 years later...

I have an intermittent problem in that I can go for 80 miles or so and everything is fine and then suddenly the overdrive relay starts chattering and dropping out. Sometimes it goes back in and sometimes not. Then after driving with in back in it works fine. On the next short drive it may or may not work fine. Just done another 100 mile trip and it was fine on the way out but started acting up intermittingly on the way back. In the garage when looking for the obvious it's working fine. Do these repro relays get hot and intermittingly fail or is it likely to be something else such as a poor connection? I've not lifted the cover off to examine the solenoid yet.

 

Paul

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I have an intermittent problem in that I can go for 80 miles or so and everything is fine and then suddenly the overdrive relay starts chattering and dropping out. Sometimes it goes back in and sometimes not. Then after driving with in back in it works fine. On the next short drive it may or may not work fine. Just done another 100 mile trip and it was fine on the way out but started acting up intermittingly on the way back. In the garage when looking for the obvious it's working fine. Do these repro relays get hot and intermittingly fail or is it likely to be something else such as a poor connection? I've not lifted the cover off to examine the solenoid yet.

 

Paul

Hi Paul,

 

I suggest that the problem lies with the switches on top of the gearbox as they can get dirty and develop internal resistance. They can be cleaned once removed with WD40 and a bit of manipulation.

 

Tim

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Hi Phil,a 33213 (old numbering system) is an SRB111(new int'l catalogue)available here:http://www.autoelectricsupplies.co.uk/product_list/113dave

Dave I followed your link and purchased a SRB111. Unfortunately none of the Lucar connections are marked at all on the new one, do you think it would be OK to assume the connection ID is the same as the original pattern in Richards pic.

Thanks

Paul

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Easy to check with a multimeter.

There should be resistance (of the coil) between the W connections.

Having determined which pins are for the coil (i.e. W1 & W2), apply 12V to these and the resistance between the other two (C1 & C2) should drop to zero as the contacts close.

Ian Cornish

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If you look at the Autoelect link page for the SRB111 you will find this wiring diagram (click on it to enlarge and you will see the connections labelled):

post-7865-0-96120300-1472992107_thumb.jpg

Edited by RobH
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Thanks Robert and Ian most helpful.

Paul

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  • 7 months later...

Hi Paul,

 

I suggest that the problem lies with the switches on top of the gearbox as they can get dirty and develop internal resistance. They can be cleaned once removed with WD40 and a bit of manipulation.

 

Tim

 

Is there a tolerance to fitting them again i.e. screwed in too little or too far, and if so how does one fit them with the correct amount of penetration through the lid?

 

When out in mine a couple of weeks ago it again started dropping out after 100 or so miles with a chatter. But when reselecting overdrive it sometimes went back in and sometimes not, but no apparent chatter. A quick drive recently showed the same symptoms but even on a short 10 mile or so run.

 

Paul

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Hi Paul,

where was the chatter coming from. The OD solenoid will chatter if the 'hold in' coils fail.

This allows the plunger to drop down and cause the 'pull in' coils to energise and try to remake the connection.

However the 'hold in' coils still will not do its job and so it chatters in and out.

 

You need to check the wiring and the solenoid.

 

Could this be caused by a dodgy GB top cover inhibit switch - may be but!!!

If you take a switch out of the top cover and press its plunger you will see how much travel it has.

You could set it up in the top cover so that operating the gear only just makes it work and then turn it in enough to take up half the travel.

This should be a decent hand tightness on a fibre washer

 

Roger

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Here you go: https://www.johnrichardssurplus.co.uk/lucas-6ra-relay-srb131-33258.html

 

But I bet it is the contacts inside the gearbox top switches which need a clean.

 

Tim

What does 'normally closed' mean on a relay operating function?

Is that correct for our overdrive operation?

 

Peter W

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Normally closed, or "NC" for short means that the contacts in the relay are connected, or "closed" when the relay coil is not energised.

This is not what you need for overdrive relay, you need "NO" - normally open.

 

I suspect the description in above link may be wrong, & it is "NO"

 

Bob.

Edited by Lebro
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