Overdrive solenoid

[TRbeginner]

Overdrive has never worked since I bought my TR5 a while ago. The relay could be heard clicking on switching into overdrive (in 2nd, 3rd and 4th) but no movement /noise from the solenoid. I recently removed the gearbox tunnel as part of an exhaust change (new brackets need etc) and decided to get to grips with the o/d problem. A quick test showed that there is 12v to the solenoid when overdrive is switched in but o/d does not engage. A quick inspection of the solenoid revealed a brown substance resembling molten resin which had run down the cylinder internally I think and solidified around the piston preventing movement and clogging up the cylinder.

 

I am assuming that replacement of the solenoid will solve the overdrive problem, but am concerned what the cause may have been. Are failing solenoids prone to overheating etc. There is no sign of any other electrical overheating/damage in the vicinity. Perhaps people could offer views based on their experiences and electrical circuit knowledge?

 

Many thanks

[peejay4A]

The A type od solenoid has two windings. One draws high current and energises only momentarily when you switch overdrive in to ensure that it pulls in firmly. The second winding then takes over to hold the solenoid in place until od is deselected. It sounds as though at some point the internal changeover contacts have failed leaving the high current winding energised all the time that od is selected and this has burned or melted the insulation as it's not intended for continuous operation. New solenoid needed.

[TRbeginner]

Pete

 

That sounds like a very plausible explanation given the symptoms. Just trying to ascertain that the cause is within the solenoid - your theory confirms that.

 

Thanks

 

David

[boxofbits]

If the windings did melt due to being switched on permanently, I'm surprised the rest of the circuit is still functional as a dead short must have taken place at some point during the 'meltdown'.

 

Might be worth checking back through the wiring etc whilst fitting a new solenoid.

 

Kevin

[peejay4A]

Molten resin doesn't sound like melted windings but it would be wise to check over the wiring.

[stuart]

The solenoid has probably not only melted the insulation but probably fried the windings too so possibly no other damage to wiring as that would have probably been obvious when it was removed. Often the failure to change over from pull in to hold in coils can be down to incorrect adjustment of the actuating lever on the solenoid side of the box. The WSM has a good description of the correct setting up of the lever to avoid this.

Stuart.