View Full Version : New OD Solinoid fried ???

01-05-2003, 02:13 PM
OK so I popped for new solinoid, relay, throttle switch and lockout switch for the BT7 sideshift. When I first adjusted the solinoid it would not go into overdrive (lever hole lined up with hole on OD). I then adjusted it just beyond the hole and it went into overdrive nicely but would not come out. I then readjusted to the halfway point and it worked great until it all warmed up. Then it would "slip out" of OD. At that time I discontinued use of OD.

Yesterday I went to readjust again and noted that the wire to the solinoid was fried open. Well I fixed the wire only to find out that the solinoid is a dead short from the wire to ground (positive/chassis/solinoid body). So I believe the solinoid is shot (new Moss part marked Lucas England).

My question is would the OD cause this? It obivously has not been rebuilt since manufacture. I have followed the various guides on adjustments for both the throttle switch and the solinoid lever.

I sure hope I don't have to pull the thing for a rebuild, but if I do what am I getting myself into? Can this be done without pulling the motor? Is there a recommended rebuilder in the SF Bay area and what kind of (ouch) cost am I in for if this is the case?


Healey 100
01-05-2003, 02:37 PM

It is possible that you adjusted the solenoid so that when engaged, it did not move the plunger far enough to open the internal solenoid contact that converts the solenoid from pull-in to holding. The pull-in coil in these units is about 1 ohm resistance, so it draws about 12 amps. The holding coil has much higher resistance, I think it only draws about 1 amp to hold the overdrive in gear.

Although the pull-in coil draws quite a bit of current, it should not in itself have fried the wires. It is possible that keeping the solenoid on in the pull-in mode overheated the solenoid, and perhaps that broke down the internal insulation leading to a short. At 12 amps, there is about 140 watts passing through the coil, enough to cause quite a bit of heat. I am sure Moss will tell you that it was your set up that damaged the unit, especially since these solenoids cost so much!

You need to figure out why the od is engaging with such difficulty and needs to be over stroked to have it transfer. Sticking in OD suggests that the drain hole in the actuating valve may be plugged, that has happened to mine. This can be cleaned without dismantling the unit, just take out the ball and plunger with a magnet and clean. I would drive the car or elevate the wheels to test the OD manually and convince yourself it is working right before putting another solenoid in it.

Good luck

Dave Russell
01-05-2003, 03:01 PM

Bill is correct.

Check out these links for more info on the OD & solenoid.






01-08-2003, 10:17 AM
One additional link that may help. <https://hometown.aol.com/bgahc/2codrepair.html>