Overdrive - relay switch

[mikeh]

In the Lucas 6RA range, the 'normally open' version used for the overdrive is an SRB111. They aren't always easy to come by at a sensible price, but there are plenty of modern equivalents available. See links below for a possible supplier & more details of Lucas relays:

 

https://www.autoelectricsupplies.co.uk/

http://vitessesteve.co.uk/PDF/Lucas-relays%20etc.pdf

 

 

Paul,

 

There's not really a lot to go wrong with these relays apart from the coil going open-circuit or the contacts getting burnt. If the coil is ok then you'll be able to hear the contacts clicking when the relay is operated. If it passes that test and you still suspect it, then gently prise the cover off and take a look at the contacts. If these look a bit black then they're easily cleaned. In addition, a continuity check while moving the gear lever as required will enable you to check the gearbox inhibitor switches without removing the gearbox cover.

 

Drop me a PM if you need any further details.

 

Regards

Mike

[LGFromage]

Interesting - so that is why my 6RA overdrive relay has a sticker saying "overdrive". Incidentally when I prised the cover off the relay the contacts were in good condition and no remedial action was necessary.

 

I still bet the problem is a dirty contact in the gearbox top switches, so either a good clean or new switches..

 

Tim

[Horse]

I come a bit late to this topic, but I had a similar problem a few years ago with the overdrive cutting in when not selected. Turned out to be the negative connection on the switch shorting on the indicator switch, The circuit diagram shows that a short to earth at the switch will bring the overdrive in. My switch is now wrapped in insulating tape! Worth a check.