RST Ski

1. whats difference between continuity and resistance?

2. can someone also break down/explain the secondary and primary
circuits on a vehicle for me?

thanks

Drewman

Continuity is basically an uniterrupted connection, a continuous flow of elecric through a circuit.

Resistance speaks for itself, something which resists the flow of current.

Can't answer the 2nd question

nilrem

what he said!!! free bump!

RST Ski

Im just reading how to test a relay, it says remove relay and attach a ohmmeter across terminals 30 and 87, then attach a wire between terminal 86 and 12, then attach a wire between 85 and earth. is then says ohmmeter should indicate continuity?

Does the above read as if your testing the relay itself or the terminals inwhich the relay sits in? cos in the manual the heading reads testing the relay

focusv8

Testing relay:

Terminal 30 and 87 are the ends of a normally open contact (no power applied to relay). No continuity will show.
Terminal 86 is one side of the relay coil, 85 is the other side.
If you put battery +ve to 86 and -ve (earth)to 85 the relay will operate continuity will show across 30 and 87.

Your text looks like you are testing the relay base primary and secondary circuit.
Load (secondary) is across 30 and 87 on the base, and should have resistance

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RST Ski

sorry ive miss read it it says attach a wire between 86 and a 12 volt supply

focusv8

Ahh.

With a meter across relay 85, 86 you should have resistance (of the coil).

85, 86 is primary cicuit
30, 87 is secondary circuit, as it only works if 85,86 want it to.

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RST Ski

so if the relay is ok what continuity reading should i get around?

focusv8

Continuity across a closed (made) relay contact should have Zero resistance.
With no power on the relay coil, continuity will not exist, Infinate resistance, (assuming normally open contact)


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RST Ski

good stuff

i got another on for you sorry

what is this test checking

multimter + probe is attach to the fuel pump earth terminal and the earth probe is attach to a earth, crank the engine and the reading on the multimeter should be a maximum of 0.25 volts

whats this checking? pump usage?

RST Ski

is this checking what voltage is coming out from the fuel pump? so if the reading was more than 0.25 volts that means the pump is faulty (or open/bad circuit) because voltage is not getting used on the pump and it slipping by? soz for my way of putting things

StephenC

think youve got a strange idea of electricity there mate. By putting the +ve on the neg of the fuel pump and the other probe on earth your detecting the volt drop across that cable, it should be as close to 0 as possible, if its higher it suggests the cable has high resistence and is consuming power. Voltage been potential difference.

RST Ski

so basicly that test is just testing the fuel pump loom?

StephenC

that part of it yes.

StephenC

just knocked you this up mate, should help explain it a little bit


showing that when the voltmeter is placed on -ve of load (bulb in this case but fuel pump in your case) and then -ve of battery/ground of car the difference 'should' be 0. When measuring across the device you get the full 12V.

RST Ski

thanks

RST Ski

Dont surpose you know much about the hall effect do you? couldnt break it down into dummy terms for me anyone? stuff i need to learn for a test

focusv8

Idiot's guide to Hall Effect:

Wack an electrical conductor (not necessarily a wire but anything that will conduct) in a magnetic field and you'll get a voltage created (generated) across that conductor as if it had become a battery.

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StephenC

this should help you bud, picture the magnet on the distibutor arm spinning around near the hall effect sensor
Hall Effect

RST Ski

cool, hows this work in say a distributer?