179580
Well-Known Member
Then that proves it is not a simple on/off relay. It is powering or taking power from 2 different circuits.Yes its marked 20/30 A and has 5 wire connection, heres a photo of the old and new;
Last edited:
Perkins 4236 short circuit someplace - how to test ignition
- Thread starter shoc
- Start date
shoc
Active Member
So I have the ignition switch back home now and would like help in testing it to see if its short circuiting -- I'm unable to read wiring diagrams but have 12v battery, wires & connectors if someone could tell me what to connect & test with a meter?
TIA
TIA
179580
Well-Known Member
So, the first thing to do is throw the battery, wires and connectors away. not needed.
Do you know what the ohms scale on the meter is? indicated by the Greek symbol Omega?
Do you know what the ohms scale on the meter is? indicated by the Greek symbol Omega?
shoc
Active Member
Great - thanks for your time on this.
Yes have meter ready and can see the various ohms selections
179580
Well-Known Member
Ok, put the meter on 200 ohms, connect the probes together and the reading will be near enough zero. That indicates a circuit exists.
shoc
Active Member
179580
Well-Known Member
From your original post, you have a truth table. Notice that when the switch is in the off position there are no little pyramids connected by a thick black line. That indicates the terminals are not connected.
Now look at the Aux/Alt in the next line and notice the little pyramids and the thick black line. Only the terminals indicated by the pyramids should be in circuit. That will be 1,2,and 4.
Now look at the Aux/Alt in the next line and notice the little pyramids and the thick black line. Only the terminals indicated by the pyramids should be in circuit. That will be 1,2,and 4.
shoc
Active Member
Probes connected to 1 +2 I get a steady near zero but between terminals 1+4 the reading is all over the place, sometimes 1, sometimes 38 to 42 and then sometimes 00.8
179580
Well-Known Member
Ok. best to scratch around with the probes to get the oxide off. But you get the idea? The next line only 1,2, and 5 should be connected.
shoc
Active Member
ahh ok I wasn't connecting 1 and 2 with one probe.
So starting from the top again;
1+2 and 4 -- steady zero
1+2 and 5 -- nothing - meter doesn't react
So starting from the top again;
1+2 and 4 -- steady zero
1+2 and 5 -- nothing - meter doesn't react
179580
Well-Known Member
And you have turned the key switch to position 2?
Caraway
Well-Known Member
Thank goodness we have stopped measuring current/voltage.
I have an old car and check suspicious loom problems ,with a meter, for continuity with power disconnected. Old looms can harden and insulation can crack leading to odd short circuits.
Some meters have a beeper for checking continuity. Quite handy.
I have an old car and check suspicious loom problems ,with a meter, for continuity with power disconnected. Old looms can harden and insulation can crack leading to odd short circuits.
Some meters have a beeper for checking continuity. Quite handy.
shoc
Active Member
opps again, key wasn't turned that time.... so now with key at position 2, I have steady zero between 1+2 and 5.
So does that show the ignition switch is fine and hasn't shorted out? If thats the case, then the suspect is the relay which is blackened and a bit melted/wonky
179580
Well-Known Member
Yes, that is what the truth table indicates. More importantly with the key in the "OFF" you should NOT have a circuit between any of the terminals. Put one of the probes on term1 and go to the remaining terminals in turn.
I am not sure what that relay is connected to but you say 5 cables are connected to it. It is a changeover relay so it either switching power from 1 source to 2 different components. or taking power from 2 different sources to one component. Pay you to trace some wires to find out.
