R500 steering wheel indicator bulb

[mikeo996]

Has anyone changed the bulb/led/switch on the indicator button on the steering wheel of a R500D?

I know there can be connection problems related to the detachable wheel, but I don’t think it’s that as the indicators are working fine, it’s just that the left hand bulb doesn’t illuminate.

The pad is just velcroed on, but I can’t see how to dismantle it further. I was wondering whether the ring around the button unscrews, but if it does it’s on tightly and I don’t want to force it. And is there a replaceable bulb or does the whole switch need replacing?

 

[mikeo996]

 

[Jonathan Kay]

Never seen those before, and can't find a reference in any of the documentation. 

Were they factory standard, and are they on any other models?

Jonathan

[mikeo996]

I think they were unique to the R500 (and the 620?).

They're a nice feature, especially compared to the usual Caterham toggle switch on the dashboard.

[Strangely]

Mike, disclaimer first: I've never seen these switches on an R500. But, they look very similar to some that I bought recently. Take a look here, and at the datasheet linked from that page:

https://uk.rs-online.com/web/p/push-button-switches/0224883/

If it is that type of switch, or similar, then the light is an LED, not a bulb, and it's not replaceable. It's also very unlikely to have blown. On the first picture that you posted, it look like there is a resistor in series with one of the switch terminals -- it looks like a red cable with some black heat-shrink over the cable and part of the resistor. That's the power feed for the LED, and so I'd check for power and continuity along that cable first.

[Strangely]

And I forgot to mention, my switches, and the ones that I pointed you to, have a threaded barrel that you push through from the front of the panel, then fasten on with a nut from behind. I can't see clearly on your photo, but it doesn't look like that, so it might be one of the type that has a plastic "finger" on the barrel, angled so that it gets pushed in as you push the button into the panel from the front, then it springs out to hold the switch in place from behind. So to remove it, you would have to find the fingers and squeeze them in, whilst pushing the switch from behind / pulling from the front. But I'd check the wiring to that LED first...

[Jonathan Kay]

The Caterham part:

Jonathan

PS: I've Asked an Expert.

 

[mikeo996]

Thanks, that’s a big help. I will investigate further.

[mikeo996]

Okay, I’ve had a play with my multimeter. With one contact at the positive terminal (red wire) and the other at the negative (black wire) I’m not getting any reading, but if I put it across the red and yellow wire’s terminals I am getting some voltage. What does this mean? (Sorry, I understand nothing about electrics).

[Jonathan Kay]

Can you post a sketch of the wiring (with colours) that you can see?

Have you got a wiring diagram: that (or the standard colours) should help identify what's coming out of the loom.

Jonathan

[mikeo996]

 

Apologies for my scrawl, but does this help?

I’m assuming that there’s also a resistor on the green wire, but it’s hard to see under black shrouding, like on the red.

 

[Strangely]

Mike, sorry if this is a bit Noddy, but I'd rather spell it out than you have to guess what I'm hinting at.

Of the four connections on the back of the switch, two are the switch, i.e. they will be connected together when you push the switch, and two are for the LED. Of the two connections that are wired together to ground, one will be one side of the switch, and the other will be a leg of the LED.

You know the switch works, because the car indicator comes on, right? So you should see about 12V between yellow and black when you push the button, or 0V if the button is not pushed. You should also be able to check for continuity or resistance between those: when the button is not pushed there will be no continuity / high resistance, when the button is pushed then there will be continuity / low resistance. If any of those are not the case, then stop because something really weird is happening.

You should also see 12V between the red and black when the button light should be on. I'm not sure how that light should behave, but if it should flash then you should see the voltage alternating between 12V and 0V. I suspect that you will see 0V regardless, and that is why the LED isn't coming on.

For the sake of sanity, do the same tests on the other button. If you can't see the resistor then you're going to have to just try it to determine, of the green and white wires, which is the switch and which is the LED. They should behave the same as the other switch, although this time you will see 12V across the LED when it is lit.

Back to the switch we're interested in. If, as expected, you don't see 12V across the LED (between the red and black wires) when the LED should be lit, then you've got a problem somewhere along the wire. If you know where the other end of the cable is, then I suggest you go right back to there and check whether there is 12V between that point and ground. If not, then the problem may be with whatever is generating the signal to the LED. If there is, then you have a problem somewhere along the wire, and you will need to look along it to find the damage.

You originally mentioned possible "connection problems related to the detachable wheel". As you can now see, the power for the LED is carried on a different wire to the switch, so it is entirely possible that the LED connection might be broken whilst the switch is working. If that is a known problem area then it would be worth checking first. Again, you can check for 12V on the relevant terminal on each side of the connector to see if it is getting across.

[mikeo996]

No, I needed all of that explanation, and having read it carefully that all makes sense. Lots to play with in the garage tomorrow!

I foresee a problem with the plug in the boss of the steering wheel, you would not believe how delicate the connectors look. Having said that I haven’t taken the wheel off recently so haven’t physically disturbed it.

[Jonathan Kay]

Answer from Ask an Expert at Caterham Parts:

Your question: Is the bulb replaceable? How does the cover come off, please? Thanks

Answer: I don't believe it is, so a new switch is the only option here I am afraid. Regards Darren

That's very quick and helpful.

Jonathan

[mikeo996]

​

You may be inclined to say “told you so”, but this is what discovered when I stopped faffing around with a micrometer and took a look under the dashboard.

For now I’ve just shoved the red wire back in the yellow port and everything is now working, but it will need a more secure fix I’m sure.

[Strangely]

Excellent, well found