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A type Overdrive Issue help please!


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Dear All,

 

I have just joined, my father has a 1972 TR6 which he has owned since 1987 (since I was 5!).

 

I have searched this excellent forum over the last couple of days (bank holiday tinker time) and have performed a few tests on the overdrive system, based on what I have found, but I am now stumped and I could really do with some help!

 

Symptoms:

Overdrive does not work in any gear.

Relay does not click regardless of stalk position, solenoid does not clunk.

(Tested with ignition on but engine off, in 2nd & in 4th)

 

I have tested the relay for resistance and it is as it should be I think: unlimited resistance across 2 connectors, about 70 ohms across the other 2.

 

I checked for continuity on the green/yellow wire (W2) from stalk switch to relay - this is good.

 

I have carried out a voltage check to each of the relay wires (W1, W2, C1 & C2) with ignition on and off, and with the switch both on and off with ignition on.

 

Results are as follows:

 

 

Ignition off:

W1 - 12.2v

W2 - 0

C1 - 12.2v

C2 - 12.2v

 

Ignition on, Switch OFF:

W1 - 11.7v

W2 - 0

C1 - 11.7v

C2 - 11.7v

(a little low as fuel pump was running - all were 11.9 with fuel pump off)

 

 

Ignition on, Switch ON:

 

W1 - 11.7v

W2 - 11.7v

C1 - 11.7v

C2 - 11.7v

 

So question is, where does this lead me?!

 

As far as I can tell, the relay is fine (although I've not heard it working yet) and the wiring to the relay from the stalk is good. I've checked the wiring diagram for the 1972 A type overdrive but it doesn't shed any light on this for me?

 

Does anyone have a suggestion as to what I can try next? I don't know anything about the inhibitor switch, is that my next check? Have I missed something obvious or checked the wrong things?

 

Do the readings look as they should?

 

Many thanks in advance!

 

Kind regards

 

Dave

 

 

 

 

 

 

 

 

 

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Dave

The volts look to be low. The solenoid takes more than 15 amps to pull in and a just a couple of amps to hold in.

If you put 12 v across w1 and w2 you should here the relay click else it may be duff.

Take the wire off c2 and put 12v on it , you should here the solenoid clunk in and out.

IF both are good take wire off w2 and check continuity to ground.

OD switch off gives an open circuit

OD switch on and in higher gears gives low or nil resistance.

Let us know how you get on

Regards

Rog

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OK - with some jumper leads I gave W1 and W2 12v across, and the relay activates / clicks. That's the first time I've heard it do that. So thank you for the tip.

 

Tried 12v to C2 but may not have done that properly! I connected positive to it and nothing happens. Then (perhaps stupidly) I connected pos and neg to it = sparks at battery! But I've not fried anything luckily, the relay still works. Phew. But nothing from the solenoid.

 

Then lastly I tested continuity from W2 to ground = nothing. But this could be due to not testing C2 properly? What's the best way to test C2 - just one positive to it from the battery?

 

This was all without keys in the ignition.

 

So in summary the relay is OK, but is not activated by the stalk. Green&Yellow W2 from stalk to relay has continuity. But no continuity from w2 at relay end to ground. however I may have buggered up the second test, 12v to C2 whch would affect that I think?

 

Thanks again!

Dave

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Dave

Put the 12v positive on the WIRE you remove from C2 and put the negative to earth to test the solenoid.

This test will bypass all other switches to test the solenoid

The car should not be running of course

 

If the relay is not pulling in you may wish to investigate this before going much further testing the solenoid etc

best of luck

rog

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Brilliant, thanks for clarifying, I will try later / tomorrow. The relay is working fine as far as I can tell so be good to see what the solenoid is up to.. Off for a beer now though.

After that I'll get it dropped off at a shop if I can't fix it.

Appreciate the help, cheers and have a good easter etc :)

Dave

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