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Overdrive relay


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I have a relay switch on a J type overdrive, according to the Moss catalogue it shouldn't have one. Not an expert on this but found original bill confirming o/d was fitted in '91'. Not sure that the car left the factory in 1972 with o/d. Am having problems with o/d and just trying to get my head round electrics

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J type no relay. However given all its doing is routing the power from a sound source if it's wire in can't think why that would negative effect. Does the overdrive have the solenoid horizontal J type or vertical A type. Relevance is the A type does use a relay. Now, what's the problem with the overdrive, not engaging g slow to engage, certain gears not working with OD, this info is required before solutions can be proposed.

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Solenoid horizontal assuming it is definitely J type, the problem I have is overdrive seems to intermittently engage on 2,3,4th gears with switch off. I have disconnected feed to solenoid I will take it out tomorrow to see if it continues. Wires and connectors looking a bit tired so hopefully it might be bad connection.

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J type should only work in 3 and 4 th gears. There are switches on top of the gearbox cover, yep gearbox tunnel cover needs to come off. These enable the overdrive to work in the requisite gears and inhibit it working in non specified gears, I.e. reverse and 1st . The A type engages 2/3/4 and the J type 3/4 only. It may be that you have the cover for an A type with a J type overdrive. With ignition on, engine off, if there is a relay in circuit you should be able to hear it click when you click overdrive switch. Check your electrics from switch, connection under dash to verify switch works, then if relay check output, finally if all thats OK, check switches on top of the gearbox top cover. Have you checked the oil level of gearbox as this is shared with overdrive and may be contributing to erratic behaviour.

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It's clear that your J type has been retrofitted so quite probable that a PO connected it up as per A type with a relay and operating on 2,3 and 4. That's how I have the J type set up on my 4A and you'll get loads of people telling you it's wrong to have od available on 2nd with a J type. Your choice but be gentle in using it in 2nd gear and it'll be fine. As Robin says, check the electrics thoroughly especially the wiring at the column switch as it shouldn't operate with the switch off (obviously).

Edited by peejay4A
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