I have often noticed when I sit in a modern motor car that there are lights providing all sorts of information.
I find myself forgetting to disengage the overdrive which comes about perhaps because the car is so quiet or I am distracted as I drift up to a set of traffic lights so that I simply forget, as I glide to a halt.
An overdrive on light might somehow remind me, when it is on.
I wondered what I could do that would not deface the dashboard in any way. The warning light cluster has no “spare” lights but that set me thinking that perhaps I could use one of the existing lights. The most obvious one is the Handbrake On light.
Then I noted that mine was not working. It was time for some investigation.
I had to remove the front seats to remove the carpet covering the handbrake mechanism and then tweak the little switch slightly so that the light came on when the handbrake was engaged. It seemed to me there was no reason at all why I could not use this light also as an overdrive on light. It does not have the correct logo on the glass but since it is not a red light – a warning, but amber and therefore a different colour it would be just fine.
Making the connections would be easy for it requires no more than two of those piggy back spade connectors, one on the handbrake switch and one on the overdrive solenoid and a couple of lengths of wire – as seen here with one of the piggy back connectors sitting just above the handbrake mechanism.
20140812-4851Pw Dolomite handbrake lever.jpg [123.88KiB |Viewed 1188 times ]
However it was not quite as easy as that for the handbrake warning light is activated when the handbrake lever switch provides the earth to the light – in much the same way as the courtesy light switches in the door pillars activate the interior light. The overdrive solenoid is activated when the gearlever switch provides 12 volts to activate it.
The solution? I used a relay which is activated when the overdrive switch activates the solenoid and then through the relay contacts it provides another earth path for the Handbrake On light.
I had some spare wires left over from one of the several Dolomites which arrived here in parts over the years. They yielded a pair of wires with the single connector which could sit alongside the wiring loom which comes up from the gearbox and which can be unplugged if and when the gearbox is removed from the car. Another piece of wire runs from the handbrake mechanism alongside the tunnel cover but on the left hand side and runs up to the relay which I have mounted in behind the glove box using one of the heater mounting bolts to hold a simple plate to which the relay has been screwed.
20140811-4849Pw Sprint overdrive indicator relay.jpg [108.16KiB |Viewed 1188 times ]
The result? Turn the ignition on and if the handbrake is activated then the indicator light will be on. It can only be the handbrake unless you happen to start the car engine in third or fourth gear with the overdrive engaged, which in my case is most unlikely. I now have a clear indication of when the overdrive is engaged.
All without defacing the dashboard nor cutting into the existing wiring in any way.
It might be of interest to some, on the other hand it might not!