Ariel Posted April 1, 2021 Report Share Posted April 1, 2021 Hi, how many amps does the overdrive servo pull please. Quote Link to post Share on other sites
RobH Posted April 1, 2021 Report Share Posted April 1, 2021 (edited) Welcome to the forum 'Ariel' - do you have a name we can use? If so you can add it as a signature in your profile if you wish. An A type overdrive solenoid draws about 16Amps initially to pull in and then about 1 Amp continuous to hold in once the internal contact has opened. Edited April 1, 2021 by RobH Quote Link to post Share on other sites
ianc Posted April 2, 2021 Report Share Posted April 2, 2021 Rob is correct - this is my note from a few years ago! Today (25/05/09), I made some measurements on a brand new, spare, overdrive solenoid which I bought from Moss some time ago. I think it is fair to assume that it was built to the same specification as the original Lucas item. Pull-in (Pull-in and Hold-in coils in parallel) 0.8 ohms, drawing about 15-17 amps. Hold-in (pull-in circuit disconnected by plunger operating the switch within the top of the solenoid) 12.5 ohms, drawing about 1 amp. For the technically-minded, this means that the Pull-in coil has a resistance of about 0.85 ohms, and takes about 14-16 amps. The current drawn will depend upon the state of charge of the battery, which is usually between 12-13.4 volts. Ian Cornish Quote Link to post Share on other sites
Ariel Posted April 9, 2021 Author Report Share Posted April 9, 2021 (edited) Thank you both, my friend wants me to fit a switch from a Spitfire to her TR. The switch is marked.. 250V.A.C 3 AMP 30V DC Do you think I will need to fit a relay? Wali Edited April 9, 2021 by Ariel Quote Link to post Share on other sites
RobH Posted April 9, 2021 Report Share Posted April 9, 2021 Yes there should be a relay Wali and if this switch is just a replacement for an existing one there ought to be a relay there already. The circuit for an A type overdrive looks like this: Quote Link to post Share on other sites
Ariel Posted April 10, 2021 Author Report Share Posted April 10, 2021 Thank you Rob, that puts by mind at ease a little. My mate Georg who owns the car has a lot of family connections with the WWii pilots and fitting this switch is special for her. Quote Link to post Share on other sites
Lebro Posted April 10, 2021 Report Share Posted April 10, 2021 Oh, that sort of Spitfire ! Strange it should be marked 250V AC Bob. Quote Link to post Share on other sites
Ariel Posted April 10, 2021 Author Report Share Posted April 10, 2021 Sorry I should have specified aviation rather than automotive! Quote Link to post Share on other sites
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