Testing the Ignition switch
The quickest test of the ignition switch is to turn it to
"start" and listen for the click from the starter
solenoid. If you hear the click the ignition switch is fine.
If you didn't hear the click, we need to find out why.
Start by testing the ignition switch circuit wiring. You will have to
find the starter solenoid. The easiest way to do this is to follow the
lead from the positive battery terminal until it connects to something.
This should be the solenoid. The starter solenoid will have several wires
attached to it, 2 very large diameter wires, and 1 or 2 small wires. (Note:
The larger the wire, the more current it can handle.) One large wire goes
to the battery the other goes to the starter. The small wire connecting to
the solenoid is the low current wire and is the control signal for the
solenoid.)
Connect the negative lead from the voltmeter and connect it to a good
ground.
Find the small wire connecting to the solenoid and disconnect the wire from
the solenoid. Connect the positive lead from the voltmeter to this wire.
Have your helper try to start the engine. Reconnect the small wire to the
solenoid. Did the volt meter go to 12V?
If no, then try the other small wire. (Depending on the type of solenoid
you have there may be only 1 terminal with a small diameter wire going to it.)
Did you now get 12V?
If yes, then that's a good thing. Your ignition switch and neutral/park
safety switch and wiring are working.
If not, then you'll have to back track to find out why.
If you are working on a '74, ensure that the driver seat belt is connected
and test again.
If you are dealing with a later model car with a manual transmission, is the
clutch depressed? You can check the clutch switch with an ohmmeter. This switch
is usually located on the clutch pedal. Disconnect the wires from the back of
the switch and connect the probes from the ohmmeter to each of the terminals on
the switch. There should be infinite resistance. Now depress the clutch pedal.
The meter should go towards 0 resistance. If the switch did not change resistance,
the it is probably bad. You can also try to bypass this switch using a jumper
wire.
The jumper wire can be any piece of wire from aligator clips to a paper clip.
Remove the wire connector from the switch. If the connector is a female (has
a hole(s) in it, take a paper clip - bend it in a "U" and press the free ends into
each of the holes in the connector. If the connector is male (has metal tabs
sticking out of the connector) you can clip an aligator clip to each of the tabs.
Try to start the engine again.
If not, I'd look at replacing the ignition switch. Since this is a generic
article, I should mention that there are a lot of different ignition switches.
In the older cars (pre 1970), they were on the dash and usually a round switch.
On most newer cars (post 1970) where you put the ignition key is not the
ignition switch. They are usually mounted on the steering column down near
the floor. When you turn the ignition switch there is a rod that goes down to
the switch and actually controls the position of the ignition switch. Sometimes
the ignition switch get loose and is allowed to move slightly. Thus when you try
to start the car, it won’t. Try moving the ignition switch either up or down the
steering column slightly, and retightening the hold down bolts. Also worth
mentioning at this point is that there is a difference in the
ignition switches for tilt and non tilt
steering columns.
Testing the Solenoid
(Low current side)
When the ignition switched was turned on and you DID get 12V, did
the solenoid go "Click"?
If yes, then the coil in the relay is OK.
IF no, and you have checked:
a. on a automatic transmission, the gear shift lever is
positioned in Park,
b. on a manual transmission, the clutch safety switch is working
then chances are that the coil in the solenoid is burned out
or you have a bad ground connection.
You can test the solenoid’s coil. Ensure the ignition is off.
Test the solenoid's input wire from the ignition switch. If it
reads 0V you can proceed with the next test. Set the multimeter
to the Ohms position. Connect the black lead to a
"ground" - almost any metal part on the car. Touch the
red lead to the connector that has the wire from the ignition
switch. If it reads 0 ohms, then the coil is probably OK. If not,
try moving the black lead, from the "ground", to the
metal mounting tab on the solenoid. If the meter reads infinite
resistance, then the coil is open, burned out. Replace the
solenoid.
If the meter reads 0 ohms then you have a bad ground or the
coil is shorted. Clean the area around the holes
on the mounting tab and the metal that the solenoid sit on with a
piece of sandpaper until the metal it is shinny and clean. Try
starting the engine again. If you don't here a click then the
wire in the solenoid has shorted out and you
will have to replace the solenoid.
Testing the Solenoid
(High current side)
Inside of the solenoid are 2 contacts that connect to the studs
(the large screws on the outside of the case). A plunger is
pulled down by the magnetic field created by the current running
through the coil when the ignition switch is turned on. The
plunger will span or short across both of the contacts, thus
allowing the high current to flow from the battery to the starter
motor.
Connect the black (negative) meter lead to a ground
(any metal part of the chassis). Connect the red (positive) lead
to the large nut on the back (pointing to the rear of the car).
There should be 12V there all the time. Have you helper try to
start the engine. Did the voltage stay above 9.5 volts?
If no, you either have a weak battery or a bad connection on
one of the battery cables. Pull both the positive and negative
battery terminals, and clean both the posts on the battery and
the connectors on the cable. (Note: you can purchase a nice
little wire brush for cleaning the upright battery posts at most
auto parts store for under $5. Also, is there some white powder
all over the battery posts? Of so, mix some baking soda and water
and pour the mixture over the battery posts. This will neutralize
the powdered acid on the posts.)
Repeat the test. If the voltage drops you probably have a weak
battery. Try jumping the car from another car.
If the voltage is above about 9.5 V, then the battery is OK
and so are the connections at the battery are fine.
Move the positive meter lead to the other large nut on the
solenoid and have your helper try to start the car. Do you get a above 9.5V? If
yes, the contacts in the solenoid are fine.
If no, did the meter show any voltage? If yes,
there is a bad connection at one of the solenoid contacts. (Disconnect the negative lead of the
battery before working on the solenoid.) Remove
both of the large wires from the solenoid. Clean the area around
the holes in the cable with a piece of sandpaper until it is
shiny and clean. Remove the low current wires from the solenoid
and remove the solenoid from the car. Clean the flat metal area
at the base of the large studs, the washers, that go on either
side of the cable, and the end of the battery cable with
sandpaper until they are nice and shinny. Reinstall the solenoid
and the wiring.
If no voltage was observed, then the contacts of the solenoid
are probably burned and will have to be replaced. On some
solenoids, you can get replacement contacts, some solenoids you
simply have to replace the solenoid.
For an explanation of the burned contacts look at the diagram.
Notice how the input contact has burned away. When the plunger
pulls down, the right side hits the full height output contact and
stops moving downward. However, it can't contact the input
contact because it has burned away.
Testing the Starter Motor Move
the positive lead to the large nut on the starter. This is
probably easiest accessed from under the car. (Remember to use
jack stands.) When your helper tries to start the car, do you get
a strong voltage reading (i.e.. greater than 9.5V)?
If yes then the output of the solenoid is OK, you have a bad
starter. Most likely it needs new brushes.
If no, then you either have a bad connection at the output of
the solenoid, or you have a bad cable from the solenoid to the
starter.
End of testing
If you attempt to work on the solenoid
or starter, DISCONNECT the NEGATIVE SIDE OF THE BATTERY BEFORE
YOU DO ANYTHING!!
Enjoy your Morgan
John
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