Relays
- Thread starter mdclear
- Start date
1.relays are generally used as a switching device. ie when you have multiple devices - amps, neons, cooling fans, etc running of a single switch source (amp remote)
2. if there was a relay originally you need to replace it with another relay of the same type as they isolate a pair of circuits.
3. see 2
2. if there was a relay originally you need to replace it with another relay of the same type as they isolate a pair of circuits.
3. see 2
a relay uses a smaller current to pull in a larger current using magetism via a coil. for example if your headlights have relays, your switch when activated switches a power through the coil in the relay to earth, the coil then pulls in contacts wich run a bigger current to your source, wich means the larger current doesnt actually go through your switch at all.
if u need a diagram to help explain ill be more than happy to draw up one
haha
if u need a diagram to help explain ill be more than happy to draw up one
haha
this pic shows a AC/DC power system, but similar applies to a car.
so lets pretend we're talking foglights.
so to power the fogs you need to hook them up to the battery. easy as. but then they're on constantly. so you put a switch in.
now you can switch them on/off. but if you want to do it easy (ie: fog light switch) you hav to run the powered wire from battery to the cabin where the switch is, and back to fog lights.
what a pain in the rectum.
This where the relay comes in. you steal some power from say the cigarette lighter, run that through the switch and down to the relay which is on the big power cord for the fogs. so now, when you flip the switch, the power goes down the wire from the cig lighter into the relay, the relay then drops the contact bridge and the full amount of battery power run directly from battery to the fogs (with out having to go up and into the cabin).
thats the jist of it :S
yeah use paulies diagram to see what im talkin about lol,
and no you should not bypass it and no it is not a safety device like a fuse so dont do anything with it lol.
and no you should not bypass it and no it is not a safety device like a fuse so dont do anything with it lol.
tryg
New Member
another good thing about a relay, either electromechanical, reed or solid state, is that the impetus wire can be rather small and the driven wire(s) can be mega amperage, depending on the relay or application.
You could have a relatively small wire to your high beam power wire which turns on some other high power driving lights. Doing this means you're not dragging all that extra load via the first wire, potentially causing a fire. Additionally, relays can act as protection as they also turn off when overloaded.
Good info, using the pics above.
You could have a relatively small wire to your high beam power wire which turns on some other high power driving lights. Doing this means you're not dragging all that extra load via the first wire, potentially causing a fire. Additionally, relays can act as protection as they also turn off when overloaded.
Good info, using the pics above.
so whats the issue? what makes u think its the relay?
plug new pump on for test run and it only goes for about 2 seconds instead of the 30 i have been told it should run for. I put a multimeter on the plug and there is no power when the key is turned to on. but if i hold it on there and have some one turn the key to on the volts come up to about 8v for about 2 seconds then go again. there is no constant power.
hmmm. i thought that was about right? because when im installing killswitches of the fuel pump, u hit the ignition on and the pump wire will prime for approx 2-3 seconds and go out, and thats how u find your fuel pump wire ( and for those people thinking why not just join it at the fuel pump? thats obviously easier to find if looking for a killswitch)
if you can get to the relay, check that there is a power at 30 (constant)
check for an earth at either 85 or 86, and whatever one wasnt should be your ignition. 87 goes to the pump.
if all those are in check and you still do not recieve a power change the relay, and the crankshaft pulley is pulsed by the computer isnt it? it pulses the earth for the sensor?
check for an earth at either 85 or 86, and whatever one wasnt should be your ignition. 87 goes to the pump.
if all those are in check and you still do not recieve a power change the relay, and the crankshaft pulley is pulsed by the computer isnt it? it pulses the earth for the sensor?
Na i was talking about the crankshaft pulse generator sensor for the firing order of the spark plugs. with the bmw's if one thing isn't working properly it will stop other things so to not cause any damage. So if the crankshaft sensor id f'ed then it won't let the pump run so to not flood engine
mdclear said:
ahhhh i see :thumbup:
mdclear said:
bloody bmw's, always make things difficult lol, why cant they be like every other car and have the relay in the engine bay... sigh...
alright let me know how u go