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tr4 overdrive not functioning


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Hi    I have no overdrive so i tightened the  loose spade connections to relay put the car in 4th gear i moved the stalk and i could hear the relay clicking.

Great i went out for a quick spin to check that the problem was solved. no joy.  Back home i again i tested the relay and it was clicking away.

now i need help as i don't know if i put back the spades in the correct position.

Is there a colour code  ?  any help would be appreciated.

thanks .

Sean.

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Sean,

could be a bad relay. Repeat your experiement & after the click reach down to the relay and waggle the C1 or C2 terminals...if you hear a much deepr click then thats the overdrive solenoid coming in...and proves the contacts of your relay are dirty.....time to replace relay.

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The relay feeding the overdrive solenoid has to work hard as it's feeding an inductive load.  Eventually, the contact in the relay gets knackered and although it may click, it may not be supplying power to the solenoid.

My TR4 has eaten about 3 relays in the past 27 years (the overdrive gets a lot of use in 2nd, 3rd & 4th).

Ian Cornish

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1 hour ago, ianc said:

The relay feeding the overdrive solenoid has to work hard as it's feeding an inductive load.  Eventually, the contact in the relay gets knackered and although it may click, it may not be supplying power to the solenoid.

My TR4 has eaten about 3 relays in the past 27 years (the overdrive gets a lot of use in 2nd, 3rd & 4th).

Ian Cornish

One option to help reduce contact wear is to put a diode between C2 and C1 so that it is reverse biased in normal operation, but shorts the connections when the relay opens. The ubiquitous 1N4007 is a suitable diode to use.

TT

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The original relay can become unreliable after time (50 years in my case according to the inscription) and although you hear the click it may work intermittently. I changed mine for a modern one given the price difference. It doesn’t look the part but functions ok.

james

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Sean

I posted the following response when this topic appeared earlier.  Worth a try?

This may be a long shot but I experienced the same problem earlier this year.  Having tried all the usual "fixes" I had it looked at by an auto electrician.  To cut a long story short the problem turned out to be dirty connections at the back of the ammeter.  If I remember correctly power was reduced as a result and despite occasionally working the usual result was a click but no engagement.  The ammeter was removed, terminals cleaned and reconnected resulting in no further problems.

As stated this may not be a "normal" problem but it would be a cheap and simple option before embarking on a more expensive solution.  Worth a try?

Bob

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  • 3 weeks later...

Hi again.  Still  trouble shooting as i did not get to continue to fix the the problem last time. I went   back to today to discover that i was looking at a relay thats  over R H side of trottle . .             When i disconnected  it i could hear clicking noise over the the clutch pedal  ( I was wondering what this other over trottle relay is for? ) i  have located the relay    and hope to fix it this weekend.

Sean. 

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