I haven't gone to look, but I'm reasonably sure my 1500 has a one-prong sender. The design is pretty simple, when pressure drops below a certain value the device links the prong to earth, so completing the circuit and causing the light to come on.
Could it be that the sender you have is an after-market sender designed to connect to a gauge, instead of the single warning light that is standard on all Spitfires? It's possible even that the sender you have is designed to supply both a gauge AND a warning light - one prong is, as you say, earth, and should be earthed to something, one is for the gauge and provides a variable resistance, and one is for the warning light and is either on or off. If you have a multi-meter, I'd suggest checking the resistance between all of the prongs with the engine off, ticking-over, and running faster (say 2,000rpm or so), and see what results you get. Richard & Daffy ---------------------------------------------------------------------- Important Notice: The information in this email is confidential and may be legally-privileged. If you have reason to believe you are not the intended recipient, any disclosure, copying, distribution or any action taken or omitted to be taken in reliance on it is prohibited and may be unlawful and you are requested to contact the sender urgently and dispose of this email -----------------------------------------------------------exp. /// [EMAIL PROTECTED] mailing list /// Send admin requests to [EMAIL PROTECTED] /// or try http://www.team.net/cgi-bin/majorcool /// Archives at http://www.team.net/archive /// Send list postings to [EMAIL PROTECTED] /// Edit your replies! If they include this trailer, they will NOT be sent.
