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MG MGB Technical - Wiper/Overdrive Switch

Greetings,

When I put the overdrive gearbox in my 68 GT, I wired it to an existing driving light switch. That decision was based on the fact that the driving lights no longer existed, and the circuit had a relay in it.

When my wipers quit during my west coast trip, I noticed that the wiper switch will click forward and backwards as well as in the direction that the steering wheel turns.

So, is it likely that my wiper switch includes the factory overdrive switch?

And then, does the overdrive need a relay?

I do have a set of driving lights that I could put on, but they would need the relay.

Thanks, Charley
C R Huff

PS:

I should have mentioned that this is a black plate, 4-syncro, dip stick transmission.

Charley
C R Huff

Charley. The wiper switch does have the overdrive switch, it doesn't require a relay. There should be a yellow wire from the switch to the bundle of connectors inside the engine bay near the fuse box.

Clifton
Clifton Gordon

Thanks Clifton,

That is good news. That location will be far more convenient. The driving light switch is on the radio panel behind the ashtray.

If I get a chance this weekend I may do the change over. Of course that will be after I figure out why the battery is going flat when the car sits a few days, and after I stick some heavier oil in the leaking front shocks!

Charley
C R Huff

Suggest you fuse the yellow power supply wire which goes to the solonoid as this wire is NOT fused whilst you are in the area
Trevor

My sentiments exactly. Simply insert an inline fuse where the yellow from the main harness joins the OD wire in the gearbox harness (either yellow or yellow/red).

While you are at it insert another where the white from the main harness joins the white in the rear harness to fuse the fuel pump as well.

Both my cars have had harness damage from shorts at the fuel pump before my ownership. Just use standard 17 amp rated, 35 amp blow fuses as you have (or should have) spares for those in the fusebox cover.
Paul Hunt 2

Thanks Trevor & Paul, (I believe I thanked Clifton already)

I have copied all the posts, and I will take your advice.

An open fire is very romantic, but not when it's in my car.

Charley
C R Huff

Has anyone ever used one of those floor switches that I believe are usually used for full beams for overdrive? It could be interesting to have the switch down beside the clutch pedal.
R Kelly

I used to drive a wolesley 6/110 with 3 speed o/d and floor mounted o/d switch (same as dip switch). It was great. It also had kickdown so when you planted your foot it dropped out of overdrive... So when I got my MGC I expected similar functionality for the overdrive... alas, no! However I've come to love flicking the overdrive switch on the dash.
James Finlayson

The 3-sync D-type overdrive had a sort-of kick-down. The system included a vacuum switch, which prevented the user switching OD out unless they were accelerating. So when cruising you could switch OD in then out again, but it would stay in, then when you accelerated it came out 'automatically'. It would switch out immediately you took it out of an OD gear though, and stay engaged if the manual switch was left on when changing between 3rd and 4th. The 'kick-down' feature is quite neat, I understand the reason for it was a marked jolt if it disengaged at any other time, but the vacuum switches were unreliable and it was dropped for the later LH-type. I was told that BL then opted for driver education instead and drivers were instructed only to disengage when accelerating, but that's not what my Drivers Handbook says - it says you can switch it in or out at any time, you don't need to feather the throttle or declutch.

I think if you were changing down from 4th to 3rd in order to accelerate having to use a footswitch would be a positive disadvantage. That's the only time the later gear-lever manual switch would be useful. For engagement and disengagement of OD whilst staying in a gear, which seems to me to be the most frequent usage, the column lever is the most convenient, anticipating by some years the paddle change.
Paul Hunt 2

With the dash mounted switch on UK spec cars, the only way you could change gear and change in or out of OD at same time is with no hands on the wheel! Unless your fingers are 2 inches longer than mine :)
James Finlayson

Maybe mine are, I can keep a thumb on the wheel while flicking the switch off. I don't think I could do that with the clutch and a floor mounted button with my ankles the age they are. However I was extolling the vitues of the *column* mounted switch, not the dash switch. I can't stretch between the gear lever and the column switch, but then it should be easy to flick that switch off as you move your left hand from the wheel to the gear lever. Although it is my V8 which has that type of switch, which only has OD in 4th anyway.
Paul Hunt 2

This thread was discussed between 29/02/2008 and 03/03/2008

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