Just something that occurred to me today...
I have Megajolt with all the usual EDIS bits. If I leave my ignition switched on with the engine stopped, am I frying my coil? Or don't the coils get charged when the engine isn't running? In the bad old days of contact breakers & coil, if the ignition was on and the points were closed, the current through the coil would eventually cook it to death.
I've asked this question on another forum (www.locostbuilders.co.uk) and the opinion there was that the coils are not energised until the VR sensor indicates that the engine is turning.
The reason for enquiring is that I've been playing around with my electrics, putting new maps in the MJ unit and so on, and the ignition is sometimes on for quite a few minutes. It would be nice to know if I need to be cautious.
I put a test meter on the coil connector and got +12v on the centre connector when the ignition is on (which is correct, of course). I had 0v on the outer 2 connectors, but I don't know whether that's open-circuit or chassis - I'm not going to risk my meter on the ohms setting to find out on a potentially live circuit!
cheers,
David
A question about MJ and EDIS
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david jenkins
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Interesting....
If the EDIS was open circuit ie there's no current through the coil(s) then you would measure 12v on the outer connectors
If the EDIS was short circuit ie there's current through the coil(s) then you would measure close to 0v on the outer connectors. I doubt you would measure EXACTLY 0v as there will be some voltage across the internal EDIS "switch"
Try a 12v 5W bulb between the outer connectors (one at a time) to ground:
- If it lights, then the EDIS is open circuit and the coils aren't conducting (well they're conducting now, to light the bulb, but they wouldn't be if the bulb wasn't there)
- If it doesn't light the EDIS is short circuit and the coils are conducting.
...and if they are conducting and they're on their way to "frying" then I would expect them to become quite warm quite quickly
I can't believe that Ford design the EDIS to have the coils conducting when there's no VR sensor signal, but if you're measuring a genuine 0v on the outer pins then that suggests they are
If the EDIS was open circuit ie there's no current through the coil(s) then you would measure 12v on the outer connectors
If the EDIS was short circuit ie there's current through the coil(s) then you would measure close to 0v on the outer connectors. I doubt you would measure EXACTLY 0v as there will be some voltage across the internal EDIS "switch"
Try a 12v 5W bulb between the outer connectors (one at a time) to ground:
- If it lights, then the EDIS is open circuit and the coils aren't conducting (well they're conducting now, to light the bulb, but they wouldn't be if the bulb wasn't there)
- If it doesn't light the EDIS is short circuit and the coils are conducting.
...and if they are conducting and they're on their way to "frying" then I would expect them to become quite warm quite quickly
I can't believe that Ford design the EDIS to have the coils conducting when there's no VR sensor signal, but if you're measuring a genuine 0v on the outer pins then that suggests they are