It will blink 10-12 times by itself after I turn the knob to the right, but when I turn the knob to the left, it won´t do a single blink unless I keep the knob to the left.
Where is the relay and can it be easily fixed? New ones available?
Thanks,
Peder
Peder,
The relay on my OTS (you don’t say what model 140 you have) is on the scuttle as below:
However, the behaviour you describe (works for one direction, and not the other) sounds more likely to be an issue with the dashboard switch. Mine behaves somewhat erratically too, but I’ve not had the courage to tamper with it, given the mysteries I’ve heard it contains…
-David
Agreed, If you have to hold the knob to make the left work there’s something wrong in the switch.
The switch is not so scary as you might think. There are three screws that hold the cover on. Once removed, you can see the contacts.
Then if you remove the three long brass screws you can get at the timer part. This is what’s inside.
The operating rod sits in the ‘V’ of the plunger and when you turn the knob it makes a contact between F and either L or R depending on which way you have turned it. At the same time it forces the plunger down against the spring pressure. There is a soft leather washer on the plunger which acts as a one way valve so that as the plunger is forced down air is expelled from the chamber.
In the bottom of the chamber there is a small hole which has a pointed screw in it. There is also a little felt filter behind the screw. When you let go of the knob the spring pushes the plunger back up and the operating rod turns the contact assembly back until it gets to the bottom of the ‘V’ when the contact is broken.
Because air can only enter the chamber slowly via the small hole it takes some seconds before the contact is broken which is the delay that is required. The exact time can be adjusted within certain limits with the pointed screw.
The trouble spots are the contacts themselves which wear after many year’s use and the leather washer which dries out or deteriorates causing the switch to flick back much too fast. Also, the Bakelite is fragile.
With mine you can see some green corrosion around the washer and also there was a problem with the contacts but it’s all fixable with a little ingenuity.
Eric
Shropshire, UK
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Eric,
Thank you for the photos and description of the switch. Maybe it will give me the courage I need to investigate. My switch operates the flashers OK, but sometimes after the switch has returned to it’s off position under the timer, the flashers start again on the same side several seconds or even minutes later. I have to wiggle the switch about it’s center position to turn them off, at which point they stay off.
-David
That could be due to wear in the contact assembly. The switch is held in the off position by a firm detent. You can’t see it in the picture but there is a ball that drops in small hole in the upper part of the assembly when the switch is off. There is quite a firm click when this happens. If you can’t feel that it might be that that part of the contacts is worn and the detent isn’t holding the switch off properly.
Eric
Thanks again Eric. My switch has no central click, so you are probably on to something. It’s been the same for the 13 years I’ve known it - maybe time to summon up some courage and dive in…
-David
There are after-market repros available from the usuals or if you’re feeling rich an eBay vendor in Malaysia has a couple of NOS ones listed at the moment but he wants a lot of money for them.
Eric
Are the repros worth trying?
Or should I remove mine and take it apart on the kitchen table?
As it works perfectly in one direction, and not at all in the other, it must be that one side is worn, dry or broken…!?
Eric … this is an interesting topic. The switch for my car is still out of my XK 140 FHC and in a storage container. While this switch is out of the car is it possible for me to simply test it by turning the knob it in one direction and the other to test the return function to the center position?
Harv,
Yes, it’s easier to operate if you put the knob on the shaft and you can watch it return to the off position and time it. 15 to 20 seconds delay seems about right which can be adjusted with the screw in the centre of the base. You could also test that the switch is actually working electrically. One way F & R are connected the other F & L.
Eric
Hi Guys,
Yes, an interesting topic. The turn signal switch on my 140 DHC returns to centre as soon as you let go of it, no delay in either direction.
This is no fun, especially when I am stopped in traffic at a red light, pointing uphill, and I want to turn left. ( I usually end up with my left hand reaching across and holding the turn signal on, and my right hand on the shifter…).
Probably the leather washer inside the turn signal switch has dried out, but I thought I would at least try adjusting the screw before trying to disassemble the whole instrument panel to try to fix it properly.
- is the air screw accessible for adjustment without removing the whole switch assembly from the car ?
- is the screw head slotted ?
- is there an easy way way to remove the switch assembly from the car ?
- is there any sense in trying to think of a way to lubricate the leather washer somehow, without removing the whole assembly from the car?
Thanks in advance for any help.
For the DHC and probably the FHC as well, the switch is located under the trim panel that closes the gap between the wooden dash top and the back of the scuttle below the windscreen. I can’t remember how this panel is fixed but I do remember that the mirror is screwed through the panel into the bracket that holds the indicator switch. The switch itself is secured via its boss with a chrome plated knurled ring. Once there is access to the switch it ought to be possible to adjust the screw, which is slotted BTW, using a very short or right-angled screwdriver.
Regarding lubricating the leather, personally I think it would be less trouble to dismantle the switch but if you removed the screw and the little felt filter pad you might be able to squirt something into the chamber through the small hole. It’s about 2mm in diameter.
If the switch flops back to off as soon as you let go of the knob I would say that there is a good chance that the leather washer has deteriorated beyond just dried out and has cracked or split and needs to be replaced. It might be simpler just to buy a replacement switch, the repros are not that expensive ca. GBP70.00.
However, if the leather is sound but just needs lubricating this raises a whole new question as to what to use. Mineral oil is probably a bad idea as in time it will destroy the leather. I have heard that Neatsfoot oil is a leather lubricant or the airgun folks use a silicone oil SM50. I suppose at a pinch a vegetable such as olive oil might do but I would like to hear other opinions on this.
Eric
Thanks so much Eric. I will get it out of storage and give it a test. In all honesty I simply never thought about testing the delay time as I just assumed it was electrical in some manner. Of course … you know what they say about assuming 
I actually developed an electrical solution to the worn-out delay problem, and Klaus Nielsen has been using it for a while now. I have not gone into production but I could do that if there was enough interest.
OK … took mine out of storage and it didn’t work at all. I have since taken it apart and as Eric mentioned, it is quite easy to do. The leather washer looks OK but I think the grease in the chamber might have become too thick with age. I now have the leather washer soaking in “3-in-one oil” which it is quite light, hence should soak into the leather over night? If anyone wants photos of what I am doing and what the switch looks like, please email me directly and I will send you some photos. BTW … my car is a 140 FHC so if there is any other info folks would like on the attachment of this switch, just let me know and I could most likely send you some photos.
Cheers … Harv
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