About to swap polarity but coil connections dont seem right?

[stan]

Hi folks I am all set to swap the polarity around tonight to negative earth however reading a few articles on this subject and looking at the ignition coil.

Swap the wires over ok well its an intermotor coil looks new but the +ve wire goea to dizzy and -ve wire to wiring loom? Surely as this is a positive earth car now shouldn't those wires have been the other way to start with?

Just want to check before I fry anything?


Thanks

[enigmas]

Hi Stan. Older style positive earth/ground ignition coils were marked SW (power from ignition switch) and CB (contact breaker)...that's fairly obvious and clear.

New style coils are marked with the symbol - (neg) on one terminal. This side goes to the distributor (the single wire if you are still running points ignition.) The other terminal is marked with a + (positive). This is the 12v feed (power to the coil) from the car's ignition switch.

NB. Having said that if you still manage to get it around the wrong way the only thing that will occur is a weaker spark at the plugs.

Nil desperandum (Vince)

[stan]

Jul 11, 2018 0:26:03 GMT enigmas said:

Hi Stan. Older style positive earth/ground ignition coils were marked SW (power from ignition switch) and CB (contact breaker)...that's fairly obvious and clear.

New style coils are marked with the symbol - (neg) on one terminal. This side goes to the distributor (the single wire if you are still running points ignition.) The other terminal is marked with a + (positive). This is the 12v feed (power to the coil) from the car's ignition switch.

NB. Having said that if you still manage to get it around the wrong way the only thing that will occur is a weaker spark at the plugs.

Nil desperandum (Vince)

Thanks for confirming Vince , thats why I wanted to check? They have put the wires on the wrong way around, eejiots.
Ok well 1 less thing to do.

Now lets see how easy this binnacle is to remove and get the ammeter swapped round, maybe a good time to swap out the bulbs for LEDs?
Ordered LED headlight bulbs and H4 headlamp unit after your recommendation, the sealed beams are fine but the way my tired eyes are these days anything that can help.😁

[enigmas]

I believe you'll find the difference in lighting amazing if not brilliant Stan! (Pun intended) Also your car's generator will appreciate the major drop in load. Expect a very white light (Don't worry about the Pearly Gates on this occasion though.

As an aside (though ignition related) over the last couple of weeks I've been 'sorting'the Programmable Ignition Module in my Coupe since a major engine/trans refurbishment. Decided to tidy up some of the extraneous wiring at the time. Being OCD at times can work against the proper functioning of some modules. In my case I had the trigger wires from the distributor (Piranha Optical switch) running too close in proximity to electrically noisy stuff. Eg. The alternator, high tension leads and the coil. This caused electrical interference with the module's ability to read the signals (rpm) for correct timing values.

The fix. Move the sensor wires away from areas producing strong interference...and use shielded cable earthed/grounded to the chassis where necessary. Live and learn.

In general though with most electrical devices on cars...ignition systems included, its either bad earths, dirty or broken connections either crimped/soldered (high resistance) or broken (open circuit). Or it can even be a coil wired up in reverse.

[stan]

Jul 11, 2018 8:41:48 GMT enigmas said:

I believe you'll find the difference in lighting amazing if not brilliant Stan! (Pun intended) Also your car's generator will appreciate the major drop in load. Expect a very white light (Don't worry about the Pearly Gates on this occasion though.

As an aside (though ignition related) over the last couple of weeks I've been 'sorting'the Programmable Ignition Module in my Coupe since a major engine/trans refurbishment. Decided to tidy up some of the extraneous wiring at the time. Being OCD at times can work against the proper functioning of some modules. In my case I had the trigger wires from the distributor (Piranha Optical switch) running too close in proximity to electrically noisy stuff. Eg. The alternator, high tension leads and the coil. This caused electrical interference with the module's ability to read the signals (rpm) for correct timing values.

The fix. Move the sensor wires away from areas producing strong interference...and use shielded cable earthed/grounded to the chassis where necessary. Live and learn.

In general though with most electrical devices on cars...ignition systems included, its either bad earths, dirty or broken connections either crimped/soldered (high resistance) or broken (open circuit). Or it can even be a coil wired up in reverse.

Thanks I have LED side and tail/stop lights already, which are great however as I am switching over to negative earth will be useless. New ones ordered.

You are not OCD you are like me, just want things to be correct and working. Funnily enough I was telling my friend with the Bentley about 90% of electrical issues will be dirty or rubbish connections. He already sorted out dim headlights.

By contrast I used to have a Datsun 100a and although they copied the Lucas connections they were all perfect, no problems. What does that tell you.😀

I had a stupid moment yesterday, drove the Rover after changing oil/filter to check for leaks, noticed the fuel gauge was on fumes, aggh best crawl to the petrol station. Put in £25 as I drive off, fuel gauge still says empty, oh no a duff gauge or bad earth, no I had somehow knocked the switch from petrol to 'oil gauge' !🤔🙄 I have a full tank of fuel now.....

[stan]

Almost done now but cant get the binnacle out properly but just enough to get to the ammeter wires, but it has 2 sets of wires brown and brown/white. Swapped both sets over so they were the same connection to each other brown to brown , brown/white to brown/white is that correct?

I switched on ignition to do the field wire flash and the ammeter went straight to -30 end of the scale? Any ideas? Usually it just sits in the middle and moves to minus when the pump kicks in?

Disconnected battery and await your advice? Do i need to switch the fuel pump over maybe?

[enigmas]

Stan if the SU fuel pump is an early points type (non electronic unit)...it doesn't care which way round it receives electricity....it's just an electromagnet (solenoid) device being activated.

As for the AMP gauge...all that should have occurred even if you left the wiring (as is) is that it would read in reverse. Re-check the wiring connecting to the Amp gauge again...and ensure you haven't accidently grounded a live wire (left off an insulating fibre washer or something similar.)

Just "quickly" flash the A and F terminals on the control box...don't hold the jumper wire there! That's what may have jambed the AMP gauge needle momentarily(?)

* Click the link below (MGA Guru) it should clarify it all for you.
There's a wealth of useful information that can be utilized on your P5 there.


mgaguru.com/mgtech/electric/et202.htm

[stan]

Jul 12, 2018 2:57:43 GMT enigmas said:

Stan if the SU fuel pump is an early points type (non electronic unit)...it doesn't care which way round it receives electricity....it's just an electromagnet (solenoid) device being activated.

As for the AMP gauge...all that should have occurred even if you left the wiring (as is) is that it would read in reverse. Re-check the wiring connecting to the Amp gauge again...and ensure you haven't accidently grounded a live wire (left off an insulating fibre washer or something similar.)

Just "quickly" flash the A and F terminals on the control box...don't hold the jumper wire there! That's what may have jambed the AMP gauge needle momentarily(?)

* Click the link below (MGA Guru) it should clarify it all for you.
There's a wealth of useful information that can be utilized on your P5 there.


mgaguru.com/mgtech/electric/et202.htm

Thanks Vince. I did check the wiring at the ammeter end first, seems ok. The fuel pump is the contacts type but why they decided on a separate one for reserve stupid idea! It will come out today and I will give it a service at least fix the reserve side which never worked since I had the car.

Have you ever seen the film Christine? Well I think Ralph is the male version! Seems to have fixed himself 😀

Just waiting on my LED headlight bulbs , H4 lamp lenses delivery, replacement side and tail LEDs (-ve earth type) and electronic ignition module (a first for me). Spending some cash on this rascal but it needs it for winter driving.

Now to fit that exhaust (just as it decides to rain today)🤔

[richardlamsdale]

"Have you ever seen the film Christine? Well I think Ralph is the male version!"

Just don't do anything to make him angry or jealous 

[stan]

Jul 12, 2018 8:33:30 GMT richardlamsdale said:

"Have you ever seen the film Christine? Well I think Ralph is the male version!"

Just don't do anything to make him angry or jealous 

Haha well it does play up when I drive my van or old mx5. 😀😀

But it must know by now I care for it the amount of time and effort and £££s I spend on it.😒

[enigmas]

Yes...I've seen the film Christine about the demonic car Stan...and its owner...from sensitive nerd to cool sociopath.

Moving on...did you find the issue with the AMP gauge?

[stan]

Jul 12, 2018 14:28:48 GMT enigmas said:

Yes...I've seen the film Christine about the demonic car Stan...and its owner...from sensitive nerd to cool sociopath.

Moving on...did you find the issue with the AMP gauge?

It was the fuel pump. I took it out cleaned up the contacts today (both sides) and reserve now works too! No more issues everything is fine.

Fitted my new replacement -ve earth LED side and tail lights and they are nice and bright but not in your face I went for warm bulbs up front.
Again maybe its my imagination buy everything seems a bit brighter now and even the fan seems to have more pep in it. Oh had to change the washer motor wires over but otherwise good. Thank you for your advice Vince.

Cant wait to fit the new headlight LED bulbs , they are quite robust looking just have to wait for the H4 headlamps to arrive. I am like a kid in a toy shop but the bank balance has taken a dip.

[enigmas]

Great result Stan...everything in life comes at a cost...but its not always in money

Could you post the details of you side lights...I wouldn't mind doing the same.

[stan]

Jul 12, 2018 21:16:23 GMT enigmas said:

Great result Stan...everything in life comes at a cost...but its not always in money

Could you post the details of you side lights...I wouldn't mind doing the same.

Agreed.

I purchased the LEDs from.

www.classiccarleds.co.uk

Front side lights

BA9S WARM WHITE LED SIDELIGHT GAUGE BULB GLB233 989

Rear stop/tail

BAY15D RED STOP / TAIL LED 4014 30 SMD BRAKE REAR LIGHT GLB380 P21/5W CLASSIC CAR NEGATIVE OR POSITIVE EARTH × 2

Both available either positive or negative earth.

I am impressed with them. Go for warm versions they are toned down but bright. The stop/tail are excellent from a safety perspective and instant response when pressing the brake.The ammeter hardly registers when they are on.

[enigmas]

Thanks Stan and Richard...what about something suitable for the dash and binnicle instrument lighting...the original lighting is abysmal!

[stan]

Jul 13, 2018 8:57:49 GMT @dicky said:

Vince, I also used the same supplier for sides & tail/brakes. There is a good contrast between the reds of the tail lamp and when the brake is applied.

The sides look good on a dull day.Headlights remain original sealed beams as the car is never driven in the dark.

I'd strongly advise anyone to change the interior lights to LED as the festoon bulbs run very hot and are a fire hazard IMO.

Dicky I said this before but your car looks stunning and my favourite colour too

[johnwp5bcoupe]

Jul 13, 2018 12:28:08 GMT @dicky said:

Vince,I changed the festoon in the selector because of the heat but left everything else.LED's are available for the binnacle lights & the old crude rheostat has to be bypassed as there's insufficient resistance for it to work.

Richard if the Rheostat is "ok" at the what should be "the brightest point" it should be a short circuit and anywhere in between it will iffy to nothing?

[enigmas]

If the rheostat is one of the switches on the left on the binnicle of a coupe controlling the "brigntness" (who are we kidding) of the instruments...I bypassed the wiring years ago as the wiring to it looked toasted (a potential fire hazard).