Overdrive stopped working mid journey

[Martin V]

GT6 late MK3

Overdrive has driven me mad this afternoon. 
The other week it wouldn’t work on a drive out. I thought I’d just tweaked the fuse holder and it worked again.

Then mid drive next time out it stopped working (didn’t switch on) again.

I went through WSM steps for diagnosis:

1. it has voltage between C1 & W2

2. Solenoid clicks in when I short the required terminals. C1& C2

3. When I earth W1 nothing happens at the solenoid and I hear do not hear the relay do anything - I have fitted brand new relay today as I was over near Moss, after already trying my spare!

4. When I earth the switch cable on my column nothing happens. I also plugged in a new switch (also picked up today) and still nothing worked with new switch.
 

Overall this suggests that the relay is faulty but I can’t keep swapping relays (although the one I originally ordered may eventually arrive).

Any ideas short of removing tunnel and ripping the wiring out and fitting a dash switch? Which I think I’ll do next time tunnel is out after summer ( any good dash switches?)

Where am I going wrong?

I did check fuse box and also fitted new fuse. Rear brake light works fine and I think from wiring that these go through same fuse ( green wire group).

help as ever appreciated😊

Edited July 16 by Martin V

[Pete Lewis]

there is often mis adjustment of the inhibitor switch , often proven by holding the gear stick to the left then the right

is the switch column mounted or on the gear knob as the wires in this installation chafe inside the stick and 

cause chaos 

column stalks are pretty reliable 

Pete

[Martin V]

25 minutes ago, Pete Lewis said:

there is often mis adjustment of the inhibitor switch , often proven by holding the gear stick to the left then the right

is the switch column mounted or on the gear knob as the wires in this installation chafe inside the stick and 

cause chaos 

column stalks are pretty reliable 

Pete

Thanks Pete.

gear knob switch and I replaced with new cables late last year when I reassembled car, also new gearbox switch and relay at that same time. Old gear box switch was short circuiting and OD was on all the time. 
By inhibitor switch I assume you mean front of gear box switch which I replaced last year? I don’t recall any adjustment just screw in to replace prior switch.

[DanMi]

there is no screw as such to adjust the inhibitor, but the switch screws into the mount and this can be adjusted see https://canleyclassics.com/?catalogue=triumph-spitfire-mkiii&diagram=triumph-spitfire-mkiii-d-type-overdrive  ok mk3 spit but they are all similar, you may need to "adjust" the bracket

[johny]

I hope you didnt earth W1 as in this diagram that would have blown a fuse. There should be 12v measuring to earth on both W1 and C1 and as you have found shorting C1 and C2 should energise the solenoid. Earthing W2 should operate the relay and also solenoid so if the first happened but not the second theres a relay problem while if neither worked the fault is with switches 60, 61 or associated wiring and earthing....

Note: I see in some of the diagrams the relay terminal numbers are crossed over ie C1/C2 = C2/C1 so probably best to go by the connected wire colours🤞 

[Martin V]

51 minutes ago, johny said:

I hope you didnt earth W1 as in this diagram that would have blown a fuse. There should be 12v measuring to earth on both W1 and C1 and as you have found shorting C1 and C2 should energise the solenoid. Earthing W2 should operate the relay and also solenoid so if the first happened but not the second theres a relay problem while if neither worked the fault is with switches 60, 61 or associated wiring and earthing....

Note: I see in some of the diagrams the relay terminal numbers are crossed over ie C1/C2 = C2/C1 so probably best to go by the connected wire colours🤞 

Thanks Johny, I’ll try the above mentioned tests. I’ve checked the fuses and all is OK. I’ve filled the WSM testing process but maybe there is a typo on point 3 if your comment is correct about W1?

[johny]

Yes thats an error in both tests 1 and 3 relative to the drawing on the same page. The manual is definitely not perfect😞 

[Martin V]

Still none the wiser.

4th relay tried today and 3rd again.

my wiring is as per diagram you copied above and I can’t see a difference between that and the one on page with test instructions. Am I missing something? 
white to W1

Brown C2

Yellow green from switch and inhibitor switch to W2

Yellow Purple Solenoid to C2

 

If I earth W2 to substitute switch and inhibitor I get no activity on solenoid. Suggesting to me Relay is faulty but this cannot be possible. I don’t see how getting no response earthing W2 can mean other switches are faulty as earthing W2 does that part of circuit instead (Earth). I double checked fuse again. Nothing makes sense.

[johny]

So definitely got 12v permanent live (ignition on) to earth on W1? When testing try to touch both meter and earth leads to the actual relay terminals and not just the wire spade connectors in order to discount poor connections between the two. Then remember the old saying: if youve discounted the possible then only the impossible remains...

[Martin V]

2 hours ago, johny said:

So definitely got 12v permanent live (ignition on) to earth on W1? When testing try to touch both meter and earth leads to the actual relay terminals and not just the wire spade connectors in order to discount poor connections between the two. Then remember the old saying: if youve discounted the possible then only the impossible remains...

Yes, I’ve had my pointy prongs of my meter onto the relay tabs W1 and earthed to chassis Earth and got nice 12.5v.

[johny]

Ok then measure what happens to this voltage when you earth the other side of the coil W2. There should be no change in it but its just possible theres a high resistance in the supply somewhere. This allow battery volts when theres no current flow but on energising the coil the voltage cant be sustained...

Also disconnect the relay and measure the resistance across W1 and W2 which may well be open circuit☹️ 

[chrishawley]

Most perplexing. For myself, given the conundrm as is, I might proceed as follows

• Take a presumptively good relay and prove it off the vehicle (i.e with w1 and w2 across a battery its operating click can be either heard of felt ,then any handy dummy load, such as side light bulb, in circuit with C1/C2 to switch on and off). Not so much an electrical test as a sanity check!

• Then (on the car) hot-wire the solenoid with two wires direct from battery positive to C1 and W1. Then with YG disconnected drop C2 to earth. If solenoid operates the reconnect YP and test again. If all now operable it does suggest the fault is upstream of the solenoid.

I am on tenterhooks to know the final diagnosis of this!

[johny]

yes just because a relay is clicking doesnt mean its contacts are making or even if they are that theyre connected internally to the relay terminals😞

[Mjit]

The easiest way to test one of the relays would be to swap over the leads from the horn relay and toot the horn.

[Martin V]

Guys, found the issue. Thanks Johny especially for your persistence with me!

 

The live feed was not stable sometimes there, mostly wasn’t. Went to ignition switch wiring and a quick fiddle and I could hear solenoid loud and clear switching on and off ( always been causes of issues from ignition early issues which cost me £££s with useless garage on wild goose chase when I said all along it will be that wiring!).

Specifically the issue lay with a wiring joint which was the PO using those horrible blue click on connectors (lazy!). I’ve got rid of that, fitted a dedicated spade female for OD wire with a piggy back male connector and then attached the other original female connector to the piggy back. All works again. I took opportunity to reroute the particular OD wire and will tied the bundle up as much away from feet. I also tagged couple of key wires from ignition barrel to make future location easy, including OD.
 

I remember someone wanted to get in my car a few weeks back (tall guy checking for size) and I guess he may have caught the terribly placed ignition barrel wires. Of course it could also have been my dainty feet.

It doesn’t take much! I’ll make some notes regarding diagnostic checks for any future issue.

Anyone need a 6RA Relay? I’ve a few🤣🤣

Edited July 18 by Martin V

[Mjit]

1 hour ago, Martin V said:

The live feed was not stable sometimes there, mostly wasn’t...Specifically the issue lay with a wiring joint which was the PO using those horrible blue click on connectors (lazy!). I’ve got rid of that, fitted a dedicated spade female for OD wire with a piggy back male connector and then attached the other original female connector to the piggy back.

Depending where it's located you might want to wrap some electrical tape around that piggyback spade.  You're talking about a live feed after all and those piggybacks aren't usually insulated and have a lot of metal exposed.  If it's nowehere near an earth then probably OK but if it's somewhere that could get knocked and make contact with an earth...

[Martin V]

2 hours ago, Mjit said:

Depending where it's located you might want to wrap some electrical tape around that piggyback spade.  You're talking about a live feed after all and those piggybacks aren't usually insulated and have a lot of metal exposed.  If it's nowehere near an earth then probably OK but if it's somewhere that could get knocked and make contact with an earth...

Thanks for the tip.