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MG MGA - Lights out

Just getting my roadster back on the road after two years. My wife said building this new house came first. Headlights, panel lights etc. don't work. Everything else(fuel pump, starter, turn signals, heater fan etc.) work with switch on. Got power to the fuse box, both top and bottom. Power on other side of fuses, bottom one when switched. No loose wires anywhere. Any ideas?

Joe Wiley

Well the MGA lights do not use a fuse, which is why so many burn out which car is it? Is power getting to the headlight , pull/twist switch?
Bob (robert) yes Y8 is toast again :)


Should we be fitting fuses to the lighting system to avoid the potential of burning out the system?

Winter's on its way, so I'm always looking for worthwhile improvment projects as an excuse to escape to the garage!

J Bray

A little trick I did.. Before I set my body to the frame I ran a heavy ground wire (I think a 6 gauge) from the ground of the battery, along the inside of the drivers frame, all the way to the front and rear of the car. It is neatly disguised so you can barley notice it. Along the way I grounded the dash, starter, all front lights and rear lights. I made sure all grounds to the dash gauges and lites came back and hit a point on this cable. This way I don't rely entirely on the electric grounding to the newly painted frame and/or body. So far it works great and I noticed more pep in my starter and less dimming of the lights!

WMR Bill


Yes, power is getting to the light switch.

Joe Wiley

Sounds like a bad earth connection
Cam Cunningham

I've had to replace two or three light switches in the last 6 years or so. Then put a relay in. Low voltage from the switch to the relay then fused wire from the fuse block to the lights. Every thing has been working fine for the last year and a half.
David Werblow

Would bad earth (ground) cause the radio, brake lights, headlights, tail lights, panel lights all to go out. If so, is there a different earth (ground) for them than the one to the turn signals, fuel pump, heater blower, that all do work. Also, if so, where is that ground. I'm the one who restored this car a few years ago and probably forgot there were separate grounds for these circuits. Does anything run through the voltage regulator? Once again I have power to and through the fuses. I have jumped directly from the headlight ground to the chassis but no luck. The leads me to believe that I'm not getting power to these items rather than a bad ground.

Joe Wiley

Joe forget the fuse box it has nothing to do with the lights.

The light switch gets it's power from the ignition switch via a brown and blue wire that is on the live side of the ignition switch and is therefore live all the time. If the car starts then this live wire ought to be OK. From the light switch it is distributed to all the circuits you describe. It can not be a bad earth as all the lights on the car have different earths, surely they are not all faulty!

I think you need to test the 2 outs on the light switch, I think you have either a faulty switch or it is wired incorrectly.

John I have installed an 8 way fuse box on my car to make sure all circuits are fused and fused seperately. The very worst thing about the lighting circuit is that power to the dashboard dimmer stat is NOT fused yet this thing is mainly metal and can very easily short to earth with terrible consequencies.

Bob (robert) yes Y8 is toast again :)


I tested both outs from the light switch. Switch is working. I've traced all of the wires. No breaks any where.

If it's wired incorrectly then a grimlin sneaked in one night and did it. I wired this thing myself, as I have done several MGs over the years, and it worked for many years until I stored it for a couple of them.

I've refered to Piet Olyslager's Tech Manual but the print on the schematic is so small I can't follow it.

Would the other items I mentioned (brake lights, horn, panel lights etc.) not work if the problem is in the light switch?

Joe Wiley

Joe the horn is on a fuse and must be totally unrelated to your lighting problem. The others are all from the lighting switch. Again what model car is it?
Bob (robert) yes Y8 is toast again :)

WMR Bill, Pennsylvania, USA. On a totally different matter, I notice you have fitted the fuel tank to the frame. You will experience great difficulty when fitting the body shell over the inlet tube on top of the tank. I suggest you remove the tank and fit it later. Good luck, the work so far looks great.
BM Gannon


Sorry I missed it earlier. It's a '60 1600 roadster. I restored it back to original. I'm one of those purist I guess. I've owned and restored several TDs, TCs, TFs and As over the last 45 years.

Everything was working fine until I put it up 2 years ago so I could devote my time to building this house in the sticks (mountains) of Georgia. It just doesn't make sense. When I restored it a few years ago I put in a new wiring harness so it couldn't be deteriorated already. Also, I have always stored it in the garage where it's warm and dry.

I'm going back under the dash today for the third time to see if I missed something.

Joe Wiley

Don't forget to check the integrity of the dip switch.

Steve Gyles

One more trip under the dash and I found it. Boy that crawling upside down under there takes its' toll. Getting old you know.

I found one of the spade ends to the hot side of the ignition switch was loose. Not totally separated but loose enough not to make contact. It was the one that connects the ignition switch to the lights and other things previously mentioned. I crimped it, put it back on and everything works.

Thanks everyone for your help.

Joe Wiley

That's what you get for using an aftermarket ignition switch. Man I hate Lucar connectors, especially for high current applications. My solution for that problem is to install a screw post barrier strip on the brace under the body cowling to take most of wires that might otherwise be connected on the back of the ignition switch. Then the ignition switch can have only two wires and carry only the current of the switched circuits. The lighting load (which is half of total vehicle current) does not have to be routed through the Lucar terminals on the ignition switch. See attached image.

Barney Gaylord


Aren't all of those wire ends (blue, yellow, red) all crimped under those plastic covers, or do you solder them? That's what failed. It wasn't the male end which is attached to the switch. Evidently when the harness manufacture made up the harness they didn't properly crimp the female end to the wire. So much for "Quality Control". It's possible that it was being held on by a couple of strands of wire before it failed. Can you imagine the heat that built up on those few strands over the years before they failed if that was it. I didn't look at it close but rather stripped the wire and put a new female spade adapter on. This time insuring it was crimped by pulling on it before installing.

Joe Wiley

Pleased you found the poor wire from the ignition to the light switch.

May I just comment on the crimps.

I hate crimps they are always a source of failure, and thus I always solder mine. I have worked in heavy industry all my life and at least one refinery I worked for banned the use of crimps and always demanded screw terminations.
Bob (robert) yes Y8 is toast again :)

Crimps are widely used in the electronics industry. They can make wonderful permanent connections if done properly. When very tightly crimped it makes what is called a gas tight joint which excludes air permeation and therefore prevents corrosion. This is almost the same as welding the metals together. If you grind through the connector you find all of the wires smashed together like a honeycomb with no air space between them, and similar between the wires and the shell.

That said, it does require that you use a proper tool to do the crimping. I used to have problems with them I was using cheap tools. When I bought a better crimping tool and learned to use it properly all of the problems vanished. I now use crimp connectors a lot, and I have not had a bad one for many years.

For those not adept at good crimping practice (no offense meant), by all means use solder and shrink tubing. Soldering is a good way to guarantee a sound connection (as long as you know how to solder). The extra time required to do the soldering may be a good investment for the home mechanic with hobby time available. If you have bought a new wiring harness, and it has bad crimp joints, you may be pretty well screwed. It could take a lot of time to solder every terminal to fix the poor quality issues.

Another problem with ALL wire connectors is insufficient support for the harness. If you leave the mass of the harness hanging on the connectors, vibration can eventually wiggle a connector loose or even break the wire near the connector. It is good practice to use a P=clip or tie-wrap to anchor the harness within 6-inches of the wire terminals.

I still hate Lucar connectors. Somewhere I think I have already explained why they are prone to failure.
Barney Gaylord

No offense taken Barney however I do not agree your logic, They are used in the electronics industry because of low current use and because they are extremely cheap!!

I have to agree however that a correct tool is paramount to getting a reasonable connection, with a cheap tool the joint is almost hopeless.
Bob (robert) yes Y8 is toast again :)

Hi, Bob (robert); crimp connections are commonly used in the telecom industry. Look at any telecom punchdown block and you'll see what Bell Labs called gas-tight cold welds all over the place. The key, as Barney said, is to use the right kind of tool. In the US, telecom supply companies like Graybar sell the appropriate tools made by companies like Crescent and Klein that will do the job, like some of the tools shown here:

No, you cannot properly crimp a connection with a pair of pliers. Neither can you property solder a connection with a bead of cold solder applied by someone with no soldering experience. If you want a belt and suspenders answer, cover the crimped connection with product like Plasti-Dip, ie;
David Breneman

I agree with Dave's comments. The cheap crimping tools (usually stamped from flat metal) are a waste of space and do nothing but a poor job. I always use terminal ends without any plastic sleeve, and crimp using a proper crimp tool with a jaw that not only crimps uniformly, but also creates a dimple in the metal sleeve of the connector, so the wire stays put. According to the tpe of termonal, I either use a correct matching nylon cover or a length of heat shrink tubing (sometimes both) to make the job insulated and durable - have never (yet) had a joint fail. It akes a little longer than just using a cheap crimp, but given that it works every time, in the long run it saves time.

dominic clancy

A crimped joint is more resistant to breakage from vibration. The wires remain flexible. In a solder joint the solder makes the wire solid up to a point and then can flex. The abrupt change causes the wire strands to break one at a time as the wire flexes.
The FAA has determined that using approved crimp connectors and the proper tool crimping is the way to go. All avionics are wired this way. Soldering is not approved.
All current production cars use crimp joints.
To keep a soldered joint from breaking there must be strain relief. Heat shrink tubing properly applied can help provide this protection.
The original bullet connector in MGAs were soldered but only at the tip. The barrel of the connector surrounded the wire insulation and provided the needed strain relief. The current Moss harness crimps near the front. The insulation is inside the barrel of the connector and provides the needed flexibility. To over solder these connections would cause early failure.
The method used to attach the wires to the voltage regulator is a good example of progress. The newer cars went from bare wire under screw terminals to crimped blade connectors. This change provided better strain relief and a surer connection.
R J Brown

> The FAA has determined that using approved crimp
> connectors and the proper tool crimping is the way to
> go. All avionics are wired this way. Soldering is not
> approved.

That is true as far as terminal ends and wire splices go, but there are plenty of places in avionics where you must solder, because crimp connectors can't be used for whatever reason. As you said, it is all about strain relief. Without proper strain relief, crimped connectors will eventually fail as well.
Del Rawlins

This thread was discussed between 08/09/2007 and 14/09/2007

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