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Landrover forward control resister ballast


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Posted (edited)

Does anyone have any idea where the resistor ballast for the ignition coil on a landrover forward control is located. Better still, a pic of where yours is located if you have a 101. I’m not getting spark at the points when I start, although I have electricity there and it sparks manually if I put a screwdriver to arc it out. I’m told that it might be due to a wire disconnected from the ballast.. but as much as I have searched, I’ve been unable to locate it. I had spark a couple of weeks ago, i then pulled the distributor out to service it and change points. Now no spark. 
 

I have the ambulance variant of the 101 
 

any help, greatly appreciated 

Edited by OZITIM
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The ballast resistor is inside the filter box & that will be a few inches away from the coil, given that the screened cable is quite short.

If you are getting sparks at the points it shows that there is continuity through the filter box & the ballast resistor is likely to be ok.

You shouldn't really be getting sparks at the CB points, it is the job of the condenser to minimise this & maybe you have the signs of a failing condenser. This would not only show itself by allowing sparks but the spark will erode the points (think of how an arc welder works).

The consequence of a spark is that it slows the collapse of the magnetic field of the coil thereby producing reduced HT. For maximum HT you need an abrupt switching off of the voltage to the coil & a good condenser should provide this.

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Posted (edited)

I checked inside the filter box. Absolutely not there. Maybe the ambulance variant is different. The wire to the distributor (off the coil) runs off the negative. Two wires are attached to the positive, both of which run back to behind the dash. One of theses wires is positive from the ignition, the other one doesn’t have any positive or negative and doesn’t appear to go anywhere, once it Trail’s back to the birds nest behind the dash. And their isn’t a ballast resister that’s I can see behind there. So I have no idea what’s going on. Should this random wire be connected to the ballast 

Edited by OZITIM
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Please post some pictures of around the coil & of the inside of the filter box. It is very difficult to visualise your set up.

From the title of the thread & at the outset you asked for the location of the ballast resistor, by that I assumed you had a 24v system. But perhaps this is not the case & it is 12v, in that case I wouldn't expect there to be a ballast resistor.

Do you think all the wiring is original or maybe a previous owner has made modifications?

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I had another search today, but could not find the ballast resister. I’ve replaced the points, condenser, and coil. I still have power to the points and will spark when I put the screw driver between the gap, with the ignition on. But once I turn the starter motor, no spark. I’m going to have to follow the two white wires that are on the positive terminal on the coil to behind the dash and try and work out what the hell is going on. Unless someone can give some sort of indication where the ballast resister is on an ambulance model. 

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Hello the ballast resister on my 12 volt 101 is on the near side of the engine bay adjacent to the coil and a pain to see/replace.

Regards Frank.

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Thanks potless, would love to see a pic, if at all possible. I will play hide and seek with it again tomorrow and see if I can find it. 

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Wherever the resistor is located it might be as well to do some preliminary checks as it may be quite ok..

The coil is a 16C6 & would have a resistance of about 1.5 ohms, the ballast resistor would have a similar resistance.

With the ignition on but not started, you should get 12v on the +ve terminal of the coil.

When you close the points this should drop to 6v. This would confirm that the ballast resistor is working.

It looks as if the ballast resistor is short circuited on running the starter motor.

Incidentally the ambulance UHB says that the basic electrical system is the same as fitted to the 12v GS.

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These don’t really help. I think I found where the mounting holes were for the ballast next to where the coil was mounted, but there is no ballast there now. I was getting spark and it was running two weeks ago, but no spark when I kick over the starter. 

7BB69E9E-9F17-4B65-8B71-C03490A0F440.jpeg

CAA3C27A-A520-4AF9-BDEA-0ACD50564CFE.jpeg

07D5FB9F-2864-496E-859F-BDD178C49D0B.jpeg

C76E437D-4180-4A1A-9A9B-723253B4726A.jpeg

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Below is where I think the ballast was originally mounted. By the look of the ignition, this ignition requires a ballast. So, either, their is a ballast relocated somewhere, or the ignition coil, despite it saying it requires a ballast, isn’t a ballast dependent coil, and the coil is no good. Thoughts? Can I just put a coil on it that doesn’t require a ballast and see what happens? 

A0DF6640-ED48-40B0-A064-F5505E476AE1.jpeg

B2760A2A-49B9-499E-B150-FDA8BD523959.jpeg

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The coil may have been changed from 6v to 12v if the ballast resistor has been removed. The original clamp with its warning may have been loosened & a 12v coil slid in. A Lucas coil should have the part number & date code stamped on the base (flat bit), this will indicate if it is 6v or 12v coil.

Maybe the ballast resistor failed & a 12v coil fitted as a temporary fix or maybe someone thought they knew better than the designers & having a 6v coil + ballast resistor was a silly complication?

Wired with a 12v coil it will still run but the performance will not be so good at high revs because the extra inductance of a 12v coil over a 6v coil slows down the rate at which the coil can magnetise & demagnetise.

In other words loading the primary with more resistance & less inductance reduces the time constant of the circuit.

 

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Running a 12volt coil in lieu of a 6 volt coil (with ballast) will make it harder to start.

When the starter is engaged the coil gets the full 12 volts so it has a fatter spark.

When you release the key it swaps to 6 volts supply to run the engine.

I think Clive is on the money with checking exactly what coil you have.

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I have power to the points. When I put a screw driver between the points it will spark.  When I turn the key, power is going to the points, however no spark. If I crank the engine, and at the same time, put a screw driver between the points it will spark, but by itself..... no spark. It’s sending me crazy. 
Particularly when I had it running fine. I have now replaced the coil, ignition switch, points, condenser. 

As a positive, I’ve almost stripped all of the old paint off. Replaced all of the suspension rubbers and steering damper. New fuel pump, water pump, recond brake and clutch masters, new tyres, etc etc  

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5 hours ago, OZITIM said:

I have power to the points. When I put a screw driver between the points it will spark.  When I turn the key, power is going to the points, however no spark. If I crank the engine, and at the same time, put a screw driver between the points it will spark, but by itself..... no spark. It’s sending me crazy. 
Particularly when I had it running fine. I have now replaced the coil, ignition switch, points, condenser. 

As a positive, I’ve almost stripped all of the old paint off. Replaced all of the suspension rubbers and steering damper. New fuel pump, water pump, recond brake and clutch masters, new tyres, etc etc  

How frustrating !

Have you checked the voltage at the coil during cranking, It may be a duff wire or connection causing a drop when under load.

Iain

Edited by Mk3iain
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Yes, it seems fine. I also ran a wire, direct from the battery to the positive on the coil, in an effort to bypass any wires, and this did not rectify the problem. So, I’m still at a loss. The fact that it was running, and then stopped is a mystery. That said, the vehicle has sat idle for at least 20 years. 

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I’m thinking of pulling out the points and condenser and putting in electronic ignition to see if that will make a difference 

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7 hours ago, OZITIM said:

 When I put a screw driver between the points it will spark.  When I turn the key, power is going to the points, however no spark. If I crank the engine, and at the same time, put a screw driver between the points it will spark, but by itself..... no spark.

 

Sparking at the points is not actually desirable, it is the Back EMF of about 300v from the primary circuit as it opens. The job of the condenser is to minimise the spark to encourage an abrupt switch off & collapse of the magnetic field to promote a high back EMF in both primary & secondary windings that add together (if the coil is designed for that polarity).

But I grant you it is some sign of life.

What voltage do you get with the points closed & the ignition on? If there is still voltage it means the points aren't making electrical contact, when you come with the screwdriver you are doing the job of the points. So it suggests there might be something in the distributor mechanism not allowing the points to make proper contact when there are meant to be closed.

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27 minutes ago, OZITIM said:

I’m thinking of pulling out the points and condenser and putting in electronic ignition to see if that will make a difference 

The first test I would do is to pull the HT lead from the coil out of the dizzy cap. Take the cap off, then hold the end of the HT lead over the centre contact of the rotor arm and spin the engine. If the spark jumps to the rotor arm then the arm is faulty and shorting to Earth. Replace rotor arm. If the spark does not jump to the arm, then hold it close a bare metal part of the engine then spin the engine, you should expect a good spark that will jump about 10mm

regards Richard

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This all started when you disturbed the distributor and its all getting very complicated. I would look to the distributor again  and look for a simple problem like a insulator missing or in the wrong place. Maybe even the timing 180 out, something simple. Hopefully.

 

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Reading your very first message my initial thought is that you have lost the distributor timing, as Iain suggests.  By all means spin it and check an HT lead to block for spark, if there isn't any check your rotor arm is turning.

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Ok, I took the distributor out and rotated it 180 degrees hoping that that might make some difference. I pulled the distributor out inspected it. All looks good, put it back in, again no spark. Still power at the points and still sparks when a screwdriver is placed in the gap, but no spark when cranking. Every part of the system has been replaced. It’s got me stumped. 

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I’m going to try putting electronic ignition in it and see what happens, but wish I could work this out before I start messing with it any further 

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27 minutes ago, OZITIM said:

Still power at the points and still sparks when a screwdriver is placed in the gap, but no spark when cranking.

Yes you have volts feeding the distributor. Put a bulb on this feed with the other end to earth & with the points open it will light up.

Presumably when you use your screwdriver the light will go out.

But what happens when you close the points by rotating the distributor or cranking?

The light should go out, if it doesn't then the points aren't closing or there is some break in the connection at the earth or the pivot post that supports the points is not free to move fully. If it is stiff it may not allow the points to relax & close fully.

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