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planojc
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-- 12-01-2011 @ 3:26 PM
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I have an Overdrive solenoid that will not always kick in on a 51 Ford. When this happens I see a large discharge on my amp gauge. Sometimes it works great and sometimes it just won’t kick in. I know that the relay and governor are not the problem. I have bench tested the solenoid with the relay many times without any failures, so my question is could there be something in the transmission keeping the solenoid plunger from moving. I have cleaned the solenoid contacts and also the mounting flange for good ground contact. Thanks
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supereal
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-- 12-01-2011 @ 5:42 PM
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The solenoid controls a part of the overdrive called a "balk ring". If it jams, the unit can't be activated. It could just be wear, or something more serious. It is likely the OD will have to be disassembled if you are sure your solenoid is at fault. The only way to know is to substitute a known good solenoid.
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MG
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-- 12-02-2011 @ 3:08 PM
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Check the wiring to the OD for frayed wires which may cause a short circuit to ground......
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supereal
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-- 12-02-2011 @ 5:38 PM
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Be aware that when the solenoid pulls, there is a high current draw, followed by a lower level as the "hold" coil takes over. If you don't see the difference, it is likely the internal contacts of the solenoid are not working.
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planojc
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-- 12-03-2011 @ 5:26 AM
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Are the hold contacts the ones located at the end of the plunger, just under the cover? I assume the other contacts on the side where the 6v terminal is located are the pull contacts. Also with the car not moving and 6v applied to the solenoid, will the solenoid only kick in if the block and the slot in the balk ring are aligned? Thanks
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supereal
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-- 12-03-2011 @ 10:14 AM
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There is only one set of contacts inside the solenoid case. When the OD is disengaged, the contacts are closed. This provides a ground for the main (pulling) coil. When the solenoid is pulled, it opens the contacts so the holding coil can take over. Power for both coils is provided by the OD relay. If the relay is not holding, check the kickdown switch. If you need a circuit diagram of the OD system, I can post one. Failure to engage the balk ring is often due to the shift rail not making a full forward travel. This can sometimes be caused by a problem with the dash control.
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planojc
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-- 12-03-2011 @ 1:08 PM
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My solenoid has two set of contacts. One on the side close to the spring, closed when disengaged, and the other is closed by the shaft on the plunger when engaged. I asume this set of contacts is for holding only. I will check to make sure the dash cable is shifting far enough. Thanks
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Texas40
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-- 12-04-2011 @ 8:32 AM
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My 50 Merc did the same thing and the problem was the ignition switch which was not sometimes not passing enough amps to the work the o/d. When I went to a separate high amp O/D switch (battery to switch to relay) and by passed the ignition switch as the current supplier the O/D worked 100% of the time.
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supereal
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-- 12-04-2011 @ 9:42 AM
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It has been a very long time since I had an OD apart, so I don't recall more than one solenoid connection, unless it is a ground. I have scanned the ciruit diagram of the unit so you can trace the wiring in your car.
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planojc
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-- 12-04-2011 @ 3:40 PM
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Thanks for the drawing. I can't see why a solenoid could be intermittent so I assume either the cable control is not all the way in or a problem with the block and balk ring. The high Amp discharge seems to be from the solenoid being energised but not far enough to close the holding coil. FYI I have found the fuse connection on the relay where the wire from the ignition switch attaches can cause a voltage drop problem due to it being held to the terminal tab by a rivet. Almost all that I have seen are loose, so by cleaning the area and using a good solder flux, I solder the fuse holder to the metal tab.
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