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Tony_C

Another OD not working

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Basis not wanting to hijack John or any other thread on same subject and suspecting my own issue is 99% down to my own increasingly incompetent meddling... I’m looking to go back and start from absolute basics.. Therefore, can anyone confirm this is the correct wiring for late 3A?0CD2464D-7816-4F55-9C2E-DA13482FF6C2.jpeg.5a9270cb12b678229d8d83338d57780d.jpeg

If so, perhaps also worth asking the question: How come mine had previously worked faultlessly for the 40+ years I’ve had the car... When the wiring set-up bears little resemblance 

 

Thanks, Tony

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Yes Tony, that diagram is correct as per the published circuits (http://www.advanceautowire.com/tr24a.pdf), but there are other possible arrangements of the same bits which will also work, so you probably had it connected in one of those alternative ways all these years.

 

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Hi Tony,

If it worked before and you have not done anything drastic I would suggest that your solenoid may be the issue. The sealing from road water does not help the operation of the solenoid. What happens is the cut off switch inside the solenoid sticks and the solenoid burns out. Not obvious from outside but a likely issue..

Do you here a click when switching the overdrive in?

Do you get a click from the relay?

What is the earth wire from solenoid? The is only one wire into it and it earths through the body not a separate earth.

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Thanks Rob, - that is a very good link and DOES bear some resemblance as to how mine is wired (ammeter to C1 on the relay etc)

 

Thanks also Rod, - yes, at least initially I did get the click when in 4th when switching. However, further ref the ‘incompetent meddling’ above, I noticed that the original relay looked superficially at least rusty so jumped to this root cause conclusion and replaced with 4A one I had hanging around - this one had  more terminals and I stuck wires on without properly checking or seeing what was C1, W1 etc.... Further to my shame, I waited until relay (and wires) got hot before realising and owning up on here... That’s why I’m going back to basics, once I’m 100% wiring is correctly back in place I can trouble-shoot from there!?

 

Again, thanks so far... hopefully, I will plod a bit further tomorrow

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I had my gearbox tunnel off in the early spring  to remedy an irregular fonctionning of the overdrive.

Have a look and test the relay first, listen for the clicking of the terminals closing. Mine was stamped 8 1968 so had lived well but was in fact the criminal - I've replaced it with a Chinese substitute.

As Rodbr says , use your ears to confirm that both the relay and the solenoid are working. - it is quite a noticeable thwack for the solenoid. The weakness as he suggests is the 'rubber' gaiter which perishes and then lets in the water and road crud. I was unable to find a gaiter replacement on its own from our regular and other suppliers - so I had to buy a new solenoid and they don't give them away! - bit of racketeering really

Tis rare that an overdrive malfunctions mechanically or hydraulically. (But it does happen!)

Don't despair!

james

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If the wiring got hot then I would really think the solenoid is dead or stuck solide and the pullin current is high before the holding switch breaks contact and load. Hold in current is low load.

They are not cheap no matter where you go and they are all much of a muchness.

Rod

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On 7/5/2019 at 3:27 PM, Tony_C said:

Basis not wanting to hijack John or any other thread on same subject and suspecting my own issue is 99% down to my own increasingly incompetent meddling... I’m looking to go back and start from absolute basics.. Therefore, can anyone confirm this is the correct wiring for late 3A?0CD2464D-7816-4F55-9C2E-DA13482FF6C2.jpeg.5a9270cb12b678229d8d83338d57780d.jpeg

If so, perhaps also worth asking the question: How come mine had previously worked faultlessly for the 40+ years I’ve had the car... When the wiring set-up bears little resemblance 

 

Thanks, Tony

As the originator of this particular diagram, I can assure you it is correct for a TR4A, but other TRs do not always have the same layout, and owners (previous or otherwise) can also make changes to suit their specific requirements. What I can tell you is it works, though I have modified my own system to suit my own requirements.

 

Kind regards

 

Tony Thomson

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Thank you Tony,

Really appreciated, I can confirm that I’m in much better shape after finding and reposting your diagram... In that I now know where I have to be with the wiring, once I have done that correctly I reckon I’m down to the following:

  1. Relay (Got original 3A, later 4A Original and new ‘Chinese) - Hoping to salvage one of the originals
  2. Check oil level (Don’t think so but will certainly check)
  3. Check solenoid (Least preferred but most likely?)

Just as an general update - Or, in fact lack of one - Best laid plans were scuppered over the weekend when I got involved with sanding oak floor....... Gosh its hard! (And doesn’t help when you get 50/50 chance of buying the correct size of belt ....)

 

Tony

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Now I’ve REALLY done some damage....

Correctly re-wired by the book (or so I thought) did not get any click(s)..... Just returned, albeit few days later, to try different relay and found this ( could have been even worse) ignition and overdrive both off with car in neutral - Time to look at this pesky solenoid but all the heat appears to have been generated at the relay?FD9DFEA4-CC80-418F-9D09-361841737292.thumb.jpeg.5764094aa6986e9a5a6a10fc8c061959.jpeg

FA0BBD1C-D335-4C51-9569-C42CEA6C949B.thumb.jpeg.561cb4adeeaff4e80ca410c7ca5637c6.jpeg

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Wow

 

looks like you only just got away with that one Tony. !!

phew !!

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Hi James, just for info here is my original relay been working fine since November 1960 (really was one of the very last off production line)... It was showing it’s age (before I cleaned it up!) but I no longer believe it was the culprit!

A2700F37-2680-4243-906B-BC9CB1C64158.thumb.jpeg.ab912aaa92414c1a2d3dcb2fe0bf03a9.jpeg

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Be careful the Overdrive relay in sidescreen TRs are not fused as far as I am aware  and the high current side of the relay if I remember correctly goes directly to the battry. If unsure of wiring always trace the wires using a multi meter, the youngest sidescreen is almost sixty years old so unless it has been rewired by yourself always be weary of the electrics

cheers

Alan

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Had an issue like this.

It was the bottom of the solenoid plunger stuck to the rubber buffer on the solenoid attachment plate lower stop. This was stopping the plunger from pulling in.  Result was melted wiring at the solenoid and burnt out solenoid primary pull-in winding.  New solenoid fixed it, bought from here for £35.00    https://www.ebay.co.uk/itm/OVERDRIVE-SOLENOID-TYPE-A-LACYCOCK-TRIUMPH-TR2-3-4-5-6-STAG-2000-2500-Etc/202722791899?hash=item2f333851db:g:4BgAAOSwSDxbveqv

Q what is the likely pull in current for a solenoid - what size fuse would protect the wiring of the pull in circuit?

Cheers

Peter W

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A real candidate for a battery master switch and use it!!!!!!!

You may now have a major problem tracing any other affected wiring. If the insulation is cooked on any other wires that ran alongside you now have a significant fire risk and you may not get away with it next time.

TIP,

If doing any electrical works that you are not super sure of, disconnect the battery when not near the car!  Disconnect it in any case with ancient wiring? You know it makes sense!

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To answer Peter W's query:

OVERDRIVE SOLENOID

Today (25/05/09), I made some measurements on a brand new, spare, overdrive solenoid which I bought from Moss some time ago. I think it is fair to assume that it was built to the same specification as the original Lucas item.

Pull-in (Pull-in and Hold-in coils in parallel) 0.8 ohms, drawing about 15-17 amps.

Hold-in (pull-in circuit disconnected by plunger operating the switch within the top of the solenoid) 12.5 ohms, drawing about 1 amp.

For the technically-minded, this means that the Pull-in coil has a resistance of about 0.85 ohms, and takes about 14-16 amps.

The current drawn will depend upon the state of charge of the battery, which is usually between 12-13.4 volts.

BTW, I've posted this info more than once before on the Forum.

Ian Cornish

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Ian's figures agree with the factory manual which gives a pull-in current of 15 amps and a holding current of less than 1 amp.

The current solenoids from Moss are ok but the ones from a few years ago had quite a high failure rate.

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