GT6 mk 3 rewire

[NonMember]

So I'm beginning to suspect your overdrive problem may be some sort of earthing fault. The rattle/buzz is caused by the two yellow wires being connected together and weakly grounded. Since the yellow/purple connects to the solenoid, it's definitely sufficiently pulled to ground for the  relay coil to think it's a short. If it's also shorted to the yellow/green then what happens when you apply power to the white wire is the relay sees 12V across the coil and turns on. As soon as it's on, there is a connection from brown to yellow/purple, so the top of the solenoid goes to 12V. The solenoid may even begin to pull in but, crucially, the yellow/green is no longer at ground, so the relay turns off. The contacts open, the yellow/purple goes back to ground, rinse and repeat.

So the next check to do is unplug the yellow/green from the relay and connect a lamp between it and brown. Does the lamp come on always, never, or only when the gearknob switch is on and it's in the 3/4 plane?

[Paul West]

An update.

Relay and solenoid both click when yellow/purple touches positive battery terminal. So they both work.

I checked all bullets and tried again. Audible click when touching positive battery lead on terminal with ignition off. Switched ignition on, put in 4th, flicked o/d in and smoke came from gearstick switch and bullets. Power therefore to switch but maybe the switch was faulty.

I’m just clutching at straws now as I followed wiring diagrams (including Colin’s) to the letter and it’s a new Autosparks loom.

Reversing lights still on all the time.

[Paul West]

Sorry Rob, have just seen your earlier post.

Will try that tomorrow but how and where could I make a better earth?

This is assuming I haven’t caused serious damage

[NonMember]

Sorry, the earthing comment was one I meant to edit when I changed my mind half way through that post! Read the rest of that post and do the test, just ignore the first sentence.

If you disconnect the yellow/purple from the relay then connecting it to +ve should not cause the relay to click, only the solenoid.

I'm afraid you've probably done some damage with your smoke-from-the-gearknob test. Please don't clutch at straws! We''re here to help and some of us have quite a lot of experience with electrical faults. You need to approach them steadily and logically, testing each bit in turn to figure out what's wrong.

The reason you got smoke was not a faulty switch. It was, however, almost certainly the same reason your relay rattles, and the same reason it clicks when you power the yellow/purple wire. And I think it may well be a short from yellow/purple to yellow/green, as I said earlier. Is there an intermediate pair of bullet connectors between the relay wiring photo and the gearbox wiring photo?

[Paul West]

Thanks Rob.

I am so grateful for your help as I have no electrical experience at all and am trying to quickly understand the process. I put in the dash wires from photos but the rest installed by an experienced TSSC member. I shall borrow a light and complete your test as directed and get back to you.

The buzzing has stopped but should there be a click when attaching the +ve lead to the +ve terminal.? That seems a new development but can’t be absolutely sure the relay did buzz on key turn as I was in the car but I will recheck.

The damage to the gearstick switch looks minimal so could snip an inch from the wire and re solder, likewise the bullet end unless you think it’s had it.

Many thanks for all your help, I am really grateful for your time and knowledge.

Paul

[NonMember]

Hopefully you got away with minimal damage at the gear knob. Depending how confident you are with soldering, it may just be more efficient to replace the damaged part, though.

What happened when you got the smoke, I suspect, was that the relay turned properly on, connecting battery to the solenoid wire, but the short from yellow/purple to yellow/green meant it also connected directly to the gearknob switch, which was closed, and connected direct to ground. Hence a short circuit from battery to ground through the relay, the switch and the unwanted short. A very big current flowed and the weakest link smoked. Unfortunately that was the switch or its local wiring. Sometimes you're lucky and the fault is the weak link (this is actually a recognised repair technique for printed circuit boards with etching defects).

The light bulb test should help confirm my suspicion on the fault. However, I note you say "the buzzing has stopped". If that means the symptoms are now different then something else has changed and we may need to re-check a few things. Which +ve lead are you referring to when you say "should there be a click"?

[Paul West]

Rob,

My mistake. The buzzing stopped as I put the yellow/purple wire on the wrong relay spade and connected to one just above the brown when doing earlier test so probably why solenoid clicked when putting +ve lead on to battery.

Back to buzzing again. Attached is the double bullet connector between relay and gearbox end. Should I change this as could be Chinese poor quality?

Will do the light test later

 

Paul

P.S. Could the smoking yesterday be related to the spade on the wrong relay pin?

[Paul West]

[Paul West]

Have changed the double bullet connector in the photo to two single ones and................no buzzing. Your suspicion of the two yellows shorting could be the problem. I won’t know the o/d works until I have repaired/ replaced the o/d gear knob switch so here’s hoping.

The reversing lights are still on though so if you can shed any light (no pun intended) on this I’d be grateful. They come on on second key phase.

[Paul West]

Rob, I changed the double bullet connector from reverse switch to loom to two singles and this has worked as well. Reversing lights now work by selecting reverse only so problem solved.

Thank you so much for your patience and help as I really couldn’t have done it without you.

Here’s hoping all’s now ok

Paul

 

 

[NonMember]

Hi Paul,

Yay! I have to confess I was rather waiting for that photo of the "double bullet connector" because it's absolutely the cause of your problem. That type is designed explicitly to connect four bullets together as a single wire, for tee'ing off branch wires. It's the wrong part and will cause the dead short between wires that I'd figured out was happening.

Hopefully you'll be sorted now.

[Colin Lindsay]

Oh Lord! That triggered a memory, exactly the same on my first Spitfire! I used a double bullet connector in place of two singles, thinking it would tidy things up, without realising that internally, the wires were all connected... and of course the reversing lights stayed on permanently. Nice to see that almost thirty years later, owners are doing the same thing!