> It seems to be the old "current-sensing" problem
Yes, as discussed here recently...

> but i dont want to put any extra components into this.
Is component count really that much of an issue?  If it is, there are
MOSFETs with extra drain and source terminals which can be used to
sense the channel current.  But you still have to measure this
proportional sense current.  That takes a little analog circuitry.


> The resistance of the glow plug is around 2-3 ohms.

Cold or Hot?

And do you need to sense the plug resistance?  Are you trying to
regulate the glow-plug temp so the engine will idle?

------------
Barry King, KA1NLH
Engineering Manager
NRG Systems "Measuring the Wind's Energy"
Hinesburg, Vermont, USA
www.nrgsystems.com