Electrical Connector (From Mr2)

[Guest Dave Skirrow]

Not quite a Robin Hood but... I've just been helping a mate out with an electrical fault on his Mk1 MR2. We have keyed it down to a connector which is shown below. Does anyone know where we can get a connector like this? Or failing that, even what they are actually called? Looks like a generic part you see on loads of cars so assuming it's not a Toyota only thing

 

[Guest Ian & Carole]

These guys should be able to help.

 

http://www.polevolt.co.uk/acatalog/Vehicle_Application_Connectors.html

 

You can just buy the steel bits, clean up the plastic shroud, ONCE you have found what caused the burning in the 1st place.

HTHs

[Guest Dave Skirrow]

Cheers! We think the burning was just a dodgy connection. Found the fault with a desperate and random wiggle test after a few hours of being logical about it.

 

Is it possible the connection was just loose or contaminated causing it to arc? Hoping a new connector will sort it.

[PaulF2B]

As only 4 terminals are used you could always cut off the connectors and use 4 crimp bullet connectors and a couple of tie wraps to tidy it up.

[Guest Dave Skirrow]

That crossed my mind but it plugs into some kind of board and I don't think they are straightforward connections to other individual wires. At worse its got a circuit board or something in it, at best each wire goes into multiple other wires. I think...

[fry61]

If it plugs into a board check the board both sides for heat damage --- there was a fair few watts of power/heat at that high resistance junction to cause the damage shown.

[Guest Dave Skirrow]

Cheers, I'll check the board out too

[Guest Dave Skirrow]

I've managed to locate it on the wiring diagrams and it looks like it's the main earth for various systems. It's pin 6 as shown on the following pic - http://screencast.com/t/aOWcYsPT

 

Is there any logical way of testing each component to work out which is causing it to overheat? I'm not great with electrics but if I attach a multimeter between the pin on the board and the pin on the connector will the resistance shoot up when the dodgy circuit is in use? ie. can I watch the meter and switch lights on and so on until I find the dodgy thing?

 

Any help much appreciated. He has a 1 week deadline now before he can no longer use his missus' car!

[sj-bradley]

It was probably just down to a loose connector where it burnt out.

 

A loose connector provides a local (higher) resistance and as power = current (squared) times resistance, any resistance will produce localised heat, which expands the connector making it looser and even higher resistance etc.

 

The saying goes: "Loose wires cause fires" which is what happened.

 

If you provide a good firm connection next time, this should not happen.

 

Simon.

[Guest Dave Skirrow]

Hi Simon, cheers for the info, I was toying with the idea of bypassing the connector and plug entirely by taking the 8 earth wires that feed into that pin and taking them all to a new earth point on the car. If what you have said is correct that I think that will solve the problem without my mate having to buy any new connectors (which he is struggling to get hold of)

 

My worry was that if you are incorrect as to the cause, and that if a faulty component (or something else) caused the overheating in that pin, then bypassing the pin will leave the fault and it might cause something else to overheat elsewhere in the circuit, and this time it might be harder to locate or may have more disastrous results.

 

Is my train of thought correct so far?

 

And if so, could we still bypass the connector and plug but fit a fuse to our new wiring so that if something other than a loose connection caused it , the fuse would blow? And how would we work out what amp fuse to fit?

 

Thanks again for your help, want to get this sorted for him but a little scared of fixing them symptom rather than the cause and leaving him with a melt loom, or worse...

[sj-bradley]

All the live feeds will already be protected by an adequate fuse as per the designers circuits.

 

Adding another fuse will not prove anything. If you look at the causes of electrical fires in houses or other properties, you will find that they all stem from one root cause - loose connections.

 

The type of connectors used is cars can be notoriously unreliable as they depend on the spring pressure forming a tight hard electrical connection. How many times have you found a plug "easy" to separate? Especially the multiplugs?

 

The only really sound connection is a properly soldered connection where the solder has "wetted" or "tinned" the wires excluding the oxides which cause high resistance.

 

It is the loose terminal which only connects in one tiny place(s) which cause a high resistance across the terminal. This causes a voltage drop across the terminal (which should NOT occur) and Volts x Current = Watts (Heat) which makes things expand. If a loose connector expands, then less of it is connected, so it forms an even higher resistance which means even more power dumped into the poor connection, so - more heat.

 

A vicious circle which is what happens when Arc Welding, so the terminal burns out.

 

Rely on the fuses already in the car to protect which is what they are for - NEVER replace a fuse with a higher rated one, the wires were not designed for the heavier load. The fuse is SUPPOSED to be the weak link.

 

Just make sure all connectors are FIRM. You can put an ohm meter across a terminal and you should get as close to ZERO ohms as possible. ANY higher than 1 ohm means a poor connector which needs to be fixed.

 

Simon.

[Guest Dave Skirrow]

Cheers again Simon, that's put my mind at ease a little. In a nutshell, are you saying that if it was another fault then the relevant fuse would have blown? So it must be a local fault to the pin (ie. loose connection)?

 

I wouldn't have replaced one of the existing fuses with a higher one. My logic was to replace the damaged pin with a new, additional fuse, in case bypassing the pin "moved" the overheating to another part of the circuit. My logic being that the fuse we added would be the weak part so we would not have to worry about something less accessible melting.

 

But I think I see what you mean now. If it wasn't a loose connection, the orginal circuit fuse for whatever the fault was would have blown?

[fry61]

Don't forget that the board into which this burnt plug located will still need an earth connection -- if replacing with a separate earth multi-wire connection.

[sj-bradley]

A fuse will only blow if there is a short circuit fault. An open circuit fault will draw no current and so will not blow.

 

If this was attached to the gauges, then there would have been a voltage drop across the poor connector and the display would have had dim lights at night or other functions which would have been erratic or not working correctly.

 

If this is the earth return as you say, it would take the combined amperage for all the gauges / lights. What size wire goes to that terminal?

 

If there is more than one wire on that terminal (Not a good idea, 2 wires max provided they are not too large), then I suggest soldering as well as crimping the connector and ensure that the connector will make a firm grip of the pin (use a loose one to check fit before putting in the multiplug)

 

Also, make sure that all terminals are clean, free of grease, dirt or oxide coating (light fine sandpaper removes oxides - usually green where copper is exposed) before connecting.

 

Simon.

[Guest Dave Skirrow]

Cheers again fellas, we've managed to modify the connector so that we can refit the pin into a different plastic slot that isn't burnt and we're going to clean up the pin the board. Hoping that'll all be enough to get him through his MOT before Friday and give him time to locate a new connector, pin a board.

 

Thanks again!