Electrical titbits


Did you know that  a condenser can  be checked with  an analog volt/ohm meter. (an analog volt/ohm  meter  has a needle).  A condenser can either have an open circuit or be shorted to ground. To check for a shorted condenser select the highest range of the ohmmeter and put the leads on the condenser, i.e. one lead on the body and one on the frame of the distributer.

If  it  is shorted, the needle will read "0" ohms (there is no resistance and a free path through the condenser to ground.)  If open, it will read the maximum resistance, or infinity (there is no current path through the windings of the condenser).  If the condenser is in good electrical condition, the needle should "kick" up the scale a certain amount, and then drift back to infinity as the condenser charges. To verify it's integrity reverse the leads to the condenser and recharge it to the opposite polarity.  Since the condenser has a charge now, the needle will generally "kick" higher than it did the first time.  Of course, this test will not indicate the condenser's integrity when it is at engine operating temperature...... PS be sure to have the ignition turned off.


The standard Lucas generator used on a Morgan +4 is rated to 22 amps continuous output. The generator will produce 28 amps continuously if it is in good condition.  At 30 amps it will start to throw solder and will shortly thereafter fail entirely.

To adjust the regulator so that the max. output is 28 amps;  Fully charge the battery and make sure that it is in good condition with clean terminals and good ground conections. Connect a ammeter in series between  the "D" terminal of the voltage regulator and the "D" wire from the generator.  (disconnect the yellow "D" wire that comes from the generator "D" teminal and connect it to one of the ammeter leads, connect the other ammeter lead to the "D" terminal of the regulator. Remove the cover from the voltage regulator. Do not disconnect any other  wires. Start the engine and turn on all of the electrical consumers at the same time.  Bring the engine up to about 3,000 RPM and read the ammeter.  Hold the RPM steady for about a minute and a half to allow the reading to stabilize. To adjust the output use the screw on the back of the regulator farthest away from the centerline of  the car.  Screwing it in will raise the output  and backing it out will lower it. The adjustment is VERY sensitive. 1/16 of a turn will make a meaurable difference.  With all of the electrical devices possible the generator cannot keep up and the system will run in a state of constant discharge and the battery will eventually go dead.  But with the headlights, trailer lights, radio and coffee pot on, the generator will  retain a positive state of charge.


Don't panic, pull over to a safe place and turn the engine off. Most people assume that the generator is at fault. This is not always the case. Look at some of the common things that can cause your generator light to come on.

Fan belt tension/deflection.

Make sure that there's about a half inch of play/deflection when you press down on the belt. If there's more than that, see if you can tighten the belt. If not, then the belt may be stretched or defective and needs to be replaced. If the belt is OK, then check the generator mounting bolts are tight. If they are nice and tight, then we can rule out a bad/loose belt or generator.

Wire harness and connectors.

Check the generator wiring harness and the connectors at the regulator.  Make sure that the wires are on good and tight and not burned or damaged. Replace any wire.connector that looks bad.


Disconnect the battery cables, negative cable first then the positive. Inspect the battery posts, for a few bucks, you can buy a battery post cleaner or use a wire brush and clean the posts and the battery clamps. For about $1.00 (USA), you can buy these little felt rings that you place over each battery posts which helps keep them nice and clean. There's also a gooey gell that you can put on the posts once the cables are re-attached to help them from corrison build up.

If you suspect that the battery has a bad cell or two, you can buy a hydrometer from any FLAPS. This simple device checks the specific gravity of the battery electrolyte in each cell. A bad cell can cause the generator/alternator to overcharge the other cells which will trigger the generator light in the speedo.

With the key in the OFF position (remove it from the ignition to be safe!) and the negative cable removed from the battery (keeping the positive cable still attached) connect a test light between the negative battery post and the disconnected negative battery cable.

If the light does not come on, then reattach the negative battery cable and move on to checking the voltage output check.

If the test light comes on, there's a short in the electrical system. You must first find out where that short/drain is coming from before we can check out charging system.

A suggestion that might help you track this down would be to disconnect the generator harness, if the light goes out then the generator/alternator is bad, if the light stays on then move to the fuse block and start removing fuses one at a time until the lamp goes out. This will at least help you figure out which components might be causing the short/drain.

Get out your digital volt meter (DVM) and check the battery voltage. A healthy 6V battery should show about +6.3VDC. A healthy 12V battery should show about +12.6VDC.

Start the engine and run it at fast idle (about 2000 RPM) and check the battery voltage again. On a 6V battery, you should be getting around +7.4VDC to +8.1VDC, on a 12V battery, you should be getting around +13.5VDC to +14.5VDC.

Flip your head lights on, the voltage should drop a bit then come back up again if the charging circuit it working properly.

If the voltages are more than what's specified, then the regulator is probably shot and needs to be replaced.

If the voltages are less than specified, then the problem lies in the generator/alternator.


Inspect the brushes first.

On generators, you can can try a simple trick; remove the brush (use a magnatized flat bladed screw driver, it will make it easier when you go to re-install the brush), the copper wire that is attached to one end is usually long enough for you to rotate the brush 180 degrees. If it is, re-install it (do this for the other brush too) and re-check the voltage outputs (the generator light may take several seconds before it goes out). If the generator light goes out and the voltages are within spec, then you have a set of worn brushes ... replace them.

If after doing this brush trick doesn't fix the problem, then you probably have a bad generator. When replacing the generator, it's a good idea to replace the regulator too. A bad generator can damage or weaken the regulator which may come back to haunt you later down the road.


Keep in mind that if you are running a generator, the generator light will glow dimly and is most noticable when it's dark (ie: at night). This is common. Ever notice when sitting at idle and you have your headlight on how *dim* the lights are at times, then when you rev the engine up over 1000 RPM they glow brighter? This is normal for a generator supplied car.

Generator Diagnostics

The ignition warning light on the combination instrument should light up when the ignition is switched on and should go out after the engine has started and the engine speed has begun to rise. The possible causes of trouble are summarised below:
 Fault   Cause   Remedy
 Warning light does not come on when ignition is switched on  a. Battery flat  a. Charge up battery
   b. Battery defective   b. Renew battery 
   c. Bulb burned out  c. Renew bulb 
   d. Battery terminal corroded or loose  d. Clean connections and if necessary tighten up
   e. Cable loose or broken  e. Tighten cable or repair
   f. Ignition switch defective  f. Renew ignition switch
   g. Generator brushes are not running on commutator  g. Free carbon brushes or renew or replace pressure springs. Do not oil carbon brushes!
 Ignition warning light does not go out when engine speed rises or flickers, glows  a. V -belt loose or defective  a. Tighten or renew belt
   b. Regulator switch defective   b, Exchange regulator switch
   c. Charging lead loose or broken  c. Check cables and connections
   d. Generator defective  d. Check generator
   e. Ignition switch lead has bad connection  e. Tighten connections
 Ignition warning light only goes out at high engine speeds  a. Generator defective   a. Check generator, repair
   b. Regulator switch defective   b. Exchange regulator switch
 Ignition warning light continues to burn after ignition switched off  a. Short to earth in cable or warning light  a. Eliminate earth short

Coil Coding Letters C.B. and S.W.

The letters C.B. refer to the contact breaker connection  on the distributor.  S.W. refers to the ignition switch connection or power into the coil.  The ignition switch is negative (is "hot" from the wire coming front eh battery) and the distributor completes the circuit to ground, or positive. First, you need to know is the car is negative or positive ground. Check the battery and see which terminal is grounded to the chassis.   Second, you need to know that older coils carried the designation CB (contact breaker) and SW (switch--ie ignition).  In a positive ground car, the white w/ black wire connects between the CB terminal and the points.  The white wire connects to the CB terminal.

If the car has been converted to negative ground, the coil should be reversed, so that CB terminal connects to the ignition (white wire) and the SW terminal connects to the the points.  If you install a newer coil with + and - terminals, rather than CB and SW, remember that how the car is grounded determines how the coil is installed and wired.  Neg ground cars have the - terminal connected to the points; Pos ground cars have the + connected to the points.  Hence:  Positive ground cars white with black wire connects to + terminal; Negative  ground cars white with black connects to the - coil terminal.

Spark Plugs on a Plus 4

Greg Solow recommends  Champion L 87YC spark plugs in a stock engine and L82YC spark plugs in an engine with 10:1  up to 11:1 compression gapped to .028 inch. He does not recommend  Bosch Platinum plugs in older engines that use any amount of oil.

Battery for a Plus 4

Geg Solow recommends replacing the two 6 volt batteries with a single group 24 12volt battery mounted on the side of the car opposite the driver to help equalize the weight distribution.  Use a Nissan battery hold down frame and a Nissan plastic battery tray to set the battery in and secure it as the originals were secured with two threaded steel rods passing through the wood floor and then through a narrow steel plate under the car.

Use nyloc nuts and flat washers on top of the battery hold down frame so as to not damage the plastic coating on the frame.  Install a new ground cable from the battery to the frame, using the same general routing and fixing location as the original that went from the left side battery. The cable will naturally have to be longer that the original. Use a battery warranteed for 5 years or longer.

An Electronic Ignition for a 1956 Plus 4
by Steve Dreiseszun for the eMOG Pub

I just wanted to report that last year when I was hot and heavy into getting some reliability in the '56 Plus 4, I wanted to install the Pertronix ignition that I'd acquired from Morgan Spares many months before.  It was sold to me as a potential solution, but no one knew whether it would fit. I procrastinated and dawdled with other things until the magic day that I  expected to drop the electronic ignition in and crank it up. It didn't fit. The breaker/base plate was a different configuration.

I called Pertronix and explained my problem and asked if there was anything  they could do?  They told me to ship them the unit and the original  distributor and they would take care of it. They turned the completed installation around within a week and shipped the set up back all at no charge.  They explained that they frequently do "one offs" and did this work in order to add to their product offerings.  This template now is in their  database, so all of you with a Plus 4/TR 2 should take advantage.  The Lucas distributor model number is important. The unit runs beautifully and is  fully contained in the housing.  It carries a full warranty from Pertronix as they did the modification, something that wouldn't have happened if I'd tried it on my own. I even converted to a negative ground at that time (important that they know this).

I highly recommend them as they took very good care of me. Pertronix Web site