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MG MG Y Type - An ignition coil and the resistor during distribut

The resistor of 25Kohm made from Lucas was inserted between distributor and an ignition coil from the purchase time at my Y-type.

((Picture))

The plug cap of the car after MGA is entering resistance. Our original plug cap does not have resistance. The Lucas resistance is not inserted in ignition circuits, such as TC-TD-YA which I looked at, until now.

Is this resistor original use?

Moreover, when it is not original what is the purpose of the insertion?

XPAG Masaaki Sakaguchi

Masaaki - The resistor is used for Radio Frequency Interference suppression. Translation, it is used to stop ignition noise from being transmitted into nearby radios. Cheers - Dave
David DuBois

I have fitted a postive earth radio in my car and I get quite a lt of crackling when the car is running - I have some capacitors that I understand I could fit - but where do I put them?
David Mullen

While the electrical guru's are about, can I ask a further question.

The earth wire from the E terminal of the regulator to the body (steering mount bracket bolt) was not fitted by PO. I have driven the car for about 1500 miles since purchase without any apparent fault.

What purpose does this earth wire provide and should I re-fit as original.

As he withdraws and bows with humble admiration to those who understand "The Prince of Darkness", thank you !

Tony
Tony Slattery

Thank you for the writing in you.

Tube radio is attached to my Y-type.
The resistance understood it as the thing for it. Thank you .
XPAG Masaaki Sakaguchi

Tony

I would connect the lead if it is there. It provides a better return/earthing route for the circuit than using the car's body/chassis/engine. Watch the ammeter after you do though to ensure you dont get over charging and if you do you will need to adjust the cut off on the control box. Least I think that is how it works!

Paul

Paul Barrow

Resistors & Capacitors-you guys are confusing.

A resitor is placed between the coil and the distributor on the primary wire to reduce the voltage at the points to extend their life. So, 12 volts from the ignition switch into the coil, and around 6 volts, but sometimes only 3-4 volts out with either a resister built into the coil, or with an external resistor, or with resistance wire (black/white) to the distributor points.

Resistance in the high tension sparkplug leads to prevent radio interference is an entirely different matter.
Scott Barrow

Thanks Paul. I will certainly check the ammeter when it is all running again.

To Scott, if you look at XPAG's photo you will see he is talking about an ignition "suppressor", or at least thats what my Grandpappy called it. It fits in-line in the high tension lead from the coil to the dizzy. I understand they are only needed for copper leads, modern carbon/silicone leads do not need "suppressing".

My personal experience with resistance coils is they have no place on an "older" MG. They don't seem to last, and the points arc just as much ?.
Tony Slattery

If the object is a television suppressor introduced in the 1950s. In those days the 405 line standard TV was broadcast on VH frequencies and passing car ignition played havoc with ones viewing. The effect was white banding across the screen and a burping noise in time with the cars engine. You could even tell which gear it was in. I think a law was passed enforcing one to be fitted - the law may still be in force. It was not intended for car radio's that is if you could afford one.
Bryan

Bryan I remember 405 line b&w TV very well - my dad's old Reliant used to play havoc with the reception if I recall. I still need to know where I fit capacitors to stop the engine on my car interfering with the old positive earth radio that I fitted - anyone any ideas.
I believe one fits on the distributor somewhere?
David Mullen

Unless you have an alternator fitted the dynamo armature will need to be fitted with a suppression diode likewise the regulator contacts, petrol pump, and maybe the windscreen wiper motor. perhaps the ignition noise could be overcome with a Bower Branson trigger. The plus & minus wireing to the radio should be of equal length and again with a diode across the lines. I am afraid its all a bit hit and miss.
Bryan

as I remember the two caps that you have , one goes on the dynamo, it should be a 0.5 microfarad metal clad cap,, it needs to be fitted to the dynamo live output terminal,, and is bolted to the dynamo end plate, the other is fitted to the coil on the switch side and bolted to the coil bracket this needs to be a one microfarad metal cased cap hope this is useful.I think that is what you are asking. if its wrong I will throw my book away.
d walker

"...a Bower Branson trigger..." - is that anything like a Bunsen Burner?? Ah, remember when TV went to 625 lines and we didn't think it could get any better! Impressive and helpful thread to us electrophobes. John.
J.P. Hall

Interesting comments about ignition suppressors. The recommended suppressor for the Y using distributor DKYH4A was as shown the in line type 78105. With the T series car it was slightly different. Although both used XPAG engines, MG decided to use the DKY4A in the sportscar engine as the vertical leads would clear the tachometer drive from the rear of the generator more easily. The H in the description of the distributor is Lucas talk for 'horizontal' meaning,of course, that the distributor cap 409635 had horizontal exit ports for leads on the saloons. T variants had vertical exit ports (Lucas didn't feel to put a V in the DKY4A making it a DKYV4A!). The recommended suppressor for the DKY4A is an elegant screw in device Lucas 78114. If your Y has got vertical exit ports on distributor cap this fits OK. Image shows 78114 on vertical 409563 cap.

M C Bath

Interesting comments about ignition suppressors. The recommended suppressor for the Y using distributor DKYH4A was as shown the in line type 78105. With the T series car it was slightly different. Although both used XPAG engines, MG decided to use the DKY4A in the sportscar engine as the vertical leads would clear the tachometer drive from the rear of the generator more easily. The H in the description of the distributor is Lucas talk for 'horizontal' meaning,of course, that the distributor cap 409635 had horizontal exit ports for leads on the saloons. T variants had vertical exit ports (Lucas didn't feel to put a V in the DKY4A making it a DKYV4A!). The recommended suppressor for the DKY4A is an elegant screw in device Lucas 78114. If your Y has got vertical exit ports on distributor cap this fits OK. Image shows 78114 on vertical 409563 cap.

M C Bath

This thread was discussed between 13/07/2008 and 13/08/2014

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