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overdrive solenoid

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overdrive solenoid
#1
  This topic is about my 1959 Austin-Healey 100-Six
awdyer Bill Dyer
Grove, OK, USA   USA
My overdrive quit working and I checked the solenoid. With power off I can move the solenoid shaft up and down freely. With the power on the shaft retracks, but will not extend. The question is... should the solenoid be spring loaded and move hard back and forth when the power is turned off and on?

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sliproc Avatar
sliproc Kevin Quistberg E
Long Beach, california, USA   USA
Bill,

As I recall when the solenoid is activated it pulls the lever on the side of the OD up and engages the OD, when it's deactivated the lever will drop down and disengage the OD. I believe the OD lever is spring loaded inside the OD.

awdyer Bill Dyer
Grove, OK, USA   USA
The spring in mine must be broken, because it moves freely when there is no power to it. I thought it might reverse the direction if the polarity on the power was changed. Thanks for the input. Bill

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ozhealey Avatar
ozhealey Tony P
Canberra, ACT, Australia   AUS
Bill,

Before you assume anything is broken, could I ask you to clarify your symptoms a little?

It looks like you are saying you can move the solenoid's plunger up and down when there is no power. So I guess you have removed the cover plate and you are manually moving it up and down with either you fingers on the plunger or you are doing it by moving the lever connected to the bottom of the plunger or perhaps the operating lever on the opposite side of the O/D unit? Regardless, with no power present this is normal.

When you then say "with power on the shaft retracts" I expect you mean when the ignition is on (car not running) and the car is in 3rd or 4th and you then turn on the O/D switch on the dash the solenoid actuates and the plunger is lifted. Again if so this is normal and assuming you dont do anything else it should stay energised and you should not be able to pull it down. If the car is not in 3rd or 4th and you turn on the O/D switch the solenoid should not actuate.

Now, if (once you have operated the O/D switch and the plunger retracts) you then simply turn the O/D switch off, nothing should happen (ie. the solenoid should remain retracted and not drop and you should not be able to put it down). This is because the solenoid is still actuated as power is still present at the solenoid until you press the accelerator pedal down and disengage the throttle switch on the engine bulkhead which in turn de-energises the solenoid.

Once the plunger is retracted and you then turn off the O/D dash switch and then hit the throttle, the solenoid should de-energise and the plunger should drop all on its own.

Cheers
Tony

awdyer Bill Dyer
Grove, OK, USA   USA
Great step by step instructions. some one has wired around the 3rd and 4th gear switch so that test is invalid. The 3rd /4th gear switch leaks oil so I assume it does not work and that is why it was bypassed. The solenoid responds as you have outlined. The only noticeable difference is that the plunger does not fall but just a little (not all the way down to the stopping point) on the way down maybe a 1/4 inch. I can use my fingers(on the attached lever on the plunger) to pull it the rest of the way down. Is there a spring that may be broke? Maybe in the overdrive unit or in the solenoid.

It appears that the solenoid and the accelerator switch is working properly, but the overdrive will not engage when driving it. Do you have any thoughts?

Thanks Bill



Edited 2 time(s). Last edit at 2017-09-08 04:30 PM by awdyer.

Michael S Avatar
Michael S Michael Salter
Dwight, Ontario, Canada   CAN
When the solenoid is powered the hole in the lever on the opposite side of the unit should line up with the hole in the case. (use a 3/16" drill to check)
Occasionally the shaft can get slightly twisted rendering this check invalid however, that is rare.
Before tearing anything apart try this.
Get the rear wheels off the ground, preferably on stands.
Loosen the clamp bolt on the solenoid arm.
Run the car in 4th gear at a moderate speed then, taking care to stay clear of the drive shaft, pull up on the check lever (the one on the side of the overdrive opposite the solenoid).
If the overdrive kicks in the fault is in the control system and can be corrected without taking the unit itself apart.
In my experience most of the problems arise from the control system rather than from the unit itself.



Michael Salter
Technical Chairman (Big Healeys)
Austin Healey Concours Committee

ozhealey Avatar
ozhealey Tony P
Canberra, ACT, Australia   AUS
Bill,

The test Michael has suggested will certainly test the operation of the O/D from a functional perspective. Let us know how it goes.

I suggest you remove and 3rd 4th bypass wiring. You only want the O/D to operate on the top gears. You need to look at replacing/fixing the switch, do this now if you can.

There is no spring in the solenoid. You can remove it very easily and then remove the plunger to look at the condition. The first solenoid I ever replaced had absorbed moisture somehow over the years and some surface rust in the hole and on the plunger shaft restricted its movement somewhat. This may be why your solenoid does not fully "drop" without a bit of finger pressure to pull it down once de-energised. Also, the small o-ring which seals the cross shaft on the end of the lever which connects to the base of the solenoid plunger may have hardened and "could" restrict free movement of the shaft and hence the final bit of the "drop".

There is a spring which operates within the mechanism associated with the solenoid, however as Kevin correctly identifies this is in the O/D unit itself under a plug at the top of the operating valve chamber. It is above the valve, which is lifted by the shaft attached to the lever which is in turn attaches to the bottom of the solenoid plunger.

This document will show you what I am talking about, page 8 gives a couple of pictures:
http://www.tonydrews.com/Overdrive/A-type%20OD%20manual.pdf

Regardless, you could prove the O/D as able to operate manually in order to begin isolate a mechanical vs electrical issue as Michael has indicated. At least you will know whether it is the O/D clutch, accumulator, pistons, etc in the O/D vs the electrical/mechanical operating valve system, although there are some common issues in the operating valve system which even when you hit the lever can stop the system from working. More on this later if necessary!!

Keep us informed.

Cheers
Tony



Edited 2 time(s). Last edit at 2017-09-11 06:30 PM by ozhealey.

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awdyer Bill Dyer
Grove, OK, USA   USA
I have looked at all the things that you all suggested and I am unable to activate the OD manually by moving the lever. with the car on jacks, running in 3rd gear, solenoid not enerzised, and pushing the lever over the hole in the casing.

Using a 3/16 screw and activating the solenoid the holes do not line up. The is a lot of slack in the solenoid shaft and lever. (noticed in the Moss catalog there is a washer on the shaft) Mine does not have this washer. I added one and the hole in the lever and hole in the case is in the correct alienment, but the OD still does not work.

The solenoid does not drop down and is very sticky, I sprayed a lubricate in it, but did not make any difference. lt looks like the solenoid shaft is in a bind and does not move straight up and down. Does that mean it is warn and needs to be replaced or can I move the lever to line up better?

I know that the book says that when the gas pedal is depressed the solenoid is deactivated. So how does the OD turn on if the solenoid is deactivated?

Thanks for the comments..it is a big help Bill

ozhealey Avatar
ozhealey Tony P
Canberra, ACT, Australia   AUS
Bill,

If you have manually operated the lever while the car is in 3rd or 4th and is driving and it goes to or even past the hole in the casing, and the O/D does not engage it unfortunately looks like an O/D mechanical/hydraulic issue. By the way, while this issue does not appear to be solenoid related, I suggest you get a new one based on your description of the current functionality.

Back to the issue....

The only thing you could do to finally check is to get in the car (tunnel cover off) and go for a drive. When you are in 3rd and doing a reasonable speed say 2000 rpm or higher, have the passenger operate the lever and hold it down (a bit safer than you doing it and driving). If it does not then work, you need to start looking at the hydraulic system in the O/D as you may not be generating sufficient pressure or you have an internal leak, or an O/D clutch issue.

The first and simplest place to start is the operating valve described in the link I provided above. Print it out and read it closely. You need to operate the lever half a dozen times to make sure any pressure is removed and then take off the top cap, there should be tension from the spring below the cap as you undo the cap. Remove and inspect the spring, take out the plunger and then the ball and inspect the ball for knicks or wear, etc. Remove the long thin valve (a magnet is a good tool here and for the ball) and then check to be sure it is not clogged down the centre of the valve or the tiny hole in the side (described in the document). A finger on one end and blowing on the other will tell you if it is OK. You need to check the seat in the O/D the ball sits on to be sure there is no obvious damage and check the seat on the top of the long thin valve lever also used by the ball. There are descriptions on how to "re-seat" both.

Replace any component which looks suspect (ball or spring mainly), re-seat with the ball, clear the valve and then put it all back together and run the tests again. If this does not work, you may have bigger issues.

If this does not work, I recommend you buy the oil pressure gauge at the following link which simply replaces the cap on top of the operating valve.

http://webspace.webring.com/people/tj/jholekamp/

With the gauge in place, go for a drive (or do the drive on blocks like you already have) and then in 3rd with a bit of speed see what pressure you are reading (should be al least 300psi for an early O/D and 400psi for the later model I think). This will tell you a great deal in terms of functionality. You should have pressure which drops when you operate the lever, but quickly returns to the original pressure while you hold down the lever.

This document explains it much better at the back. http://vintagetriumphregister.org/maintain/TransRebuild/OverDriveA02.pdf

This will tell you if you need to do a rebuild of the O/D.

Cheers
Tony

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awdyer Bill Dyer
Grove, OK, USA   USA
I know that a lot of time has pasted since I last commented on this problem, I've been out of town.

I have the problem resolved and it was wired incorrectly on the relay switch, when it was restored years ago. The connections for terminals W2 and C2 on the relay switch were crossed. The overdrive works great now that I switched these wires based on the color code of the wires. The white/green on C2 and white/purple on W2. Also replaced the 3/4 gear switch while I had the tunnel off.

I don't know how or why the overdrive worked sometimes with this configuration, but I was on a long goose chase finding this one....Goes to show you not to assume anything, check everything.....

Thanks for all the input on this issues. Bill

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