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Overdrive problem when raining - bj8

Danne

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Hi all!


Hi all!

My overdrive has started to act up. Lets say I have been driving for 30 min, then the OD won’t engage, or will engage after a while when switched on, or will engage as it should. There seems to be no logic when it works or not. This problem I knew.


But. Last week it also started to act up when it was raining outside. And now it seems that if it’s just moist outside it won’t work.


I have done some testing:
When the car is standing still, with the ignition on, I hear the solenoid “click” on gear 3 and 4. So it works as it should. But as soon as I start driving it won’t work.


I have tried to jerk the shift stick around when driving in gear 3 and 4, but nothing happens.


When everything is dry outside everything works, the OD engages correctly when driving.


Anyone have a clue what’s going on here?


/Danne
 

Healey 100

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Danne:

I believe your problem is high resistance in the contacts inside the solenoid. These contacts direct the power to the low resistance pull-in coil in the solenoid. Just a few ohms resistance significantly weakens the solenoid. It takes quite a bit of force to pull the lever when the OD is pressurized. The clicking you hear when the car is stopped does not mean the solenoid is OK, it will click when energized but does not have the power to actually engage the OD.

Another less likely possibility is a poor ground between the solenoid/transmission/frame. This could also be affected by moisture. As with the contacts, you only need a small resistance to weaken the solenoid enough to keep the OD from engaging.

You can try to clean the solenoid contacts, they are under the cover on top of the solenoid -- but I haven't had much luck cleaning them. When cleaned they work better for a while but they will still act up again. I think the best solution is to get a new solenoid, there now are repro units for a reasonable price.

You can check the resistance between the solenoid and ground: it should be just a fraction of an ohm when the OD is disengaged. Check your wiring diagram to see how to make this measurement, I think it can be done without removing the tranny cover.
 

Rob Glasgow

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I had a similar problem, although it had nothing to do with moisture. Turned out to be loose wire connections on the back of the dash switch. Once I tighten those, it worked fine.
 

Keoke

Great Pumpkin
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I'm of the poor electrical connection group TOO, some place in the circuit.
 
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Danne

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I recently replaced the switch on the dash board, because I had similar thoughts like you Rob. It felt like something was loose on the back. But since I have replaced that one it feels that it have to be something else. But, yes, the poor connection group seems like the team to be on;).

Today when I drove to work it worked fine (and it was dry and sunny today) the first two times I used the OD, the third (after driving approximately 5 min) didnt work. After that it didn't work anymore during the ride. I stopped at a bus station and tried it when standing still. Yes, no problems. Then it works. But when I started driving again it didn't work. Really strange.
 

healeyblue

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Just because you hear it clicking doesn't mean the solonoid is traveling far enough. There is an adjustment for the travel of the arm that the solenoid operates. Maybe check that. The easiest way to troubleshoot though is to drive with the trans cover removed so you can access things quickly for testing.
 
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Heat in the wiring and contacts also increases resistance, and possibly the same high resistance was the cause of your dash-switch going bad (high heat softens the plastic, the contacts are then less tight and the cycle continues to repeat itself).

Start to finish, from the white wires on the fuse block through to the the last wire on the solenoid, I would remove and clean the connections, snugging up the push-on connectors as I went (needle-nosed pliers do a good job here). Removing them one at a time will keep you out of trouble, and for the sake of trouble-shooting, I always stick both of the throttle switch wires under one terminal, effectively eliminating it from the circuit. You can revisit that, putting the throttle switch back in service, once the fault has been corrected.

Removing the trans cover on a BJ8, with the full dash and center console is a hateful job, so if you can comfortably access all the devices with it on, you may not need to go down that path! I would check all the connections before playing with the clamped rod on the operating shaft, since it does work some of the time...
 
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Danne

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Thanks for your help guys. I really really appreciate it.

Seems as the problem must be electrical then.

The previous owner of the car has made some strange modifications. Right now I have a light diode on the dashboard that indicates if the OD is engaged. There is a switch/pedal under the car next to the gearbox (or solenoid, forgive me I don't know that much yet about the car), so when the OD kicks in it flips the pedal/switch and the light diode starts to shine. The throttle switch is bypassed (don't know why the previous owner did that, maybe its broken). I also have a AMP-meter that indicates when power is changed in the system. It always indicate a change when I flip the OD-switch. Even if the OD isn't engaged, I can see that the power is changed.
 
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Danne

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I haven't had the time yet, to check the cables. Yesterday I was driving home from work and the OD didn't work at all. I had the switch on and off for a while and suddenly I felt that it actually melted inside, it lost the "switch/snap feeling" (no on/off click). My center console and dash aren't screwed together (so I can reach in with my fingers to feel the switches). Today I spoke to a mechanic about the problem. He thinks it might be a mechanical problem that causes the OD not to engage.

He describes it like this. The OD is operated by two spools. One generates much power, this is the one that "engages" the OD. The other one generates less power, and holds the OD engaged (which need less power). If the "large" spool don't engage the OD properly (lets say it goes half way in), it will not stop generating power. This will cause cables and switch to melt.

This might explain why there is a light diode telling if the OD is engaged. Its simply a warning sign saying "if the diode doesn't shine, don't put the OD switch in "on-position".

So, he thinks the OD has to be renovated, which is a pretty costly job I presume.

It seems like this mechanic is into the same thoughts as Bill, above. The question - I guess - is then, is it the solenoid, or something in the OD that makes it hard for the OD to engage all the way? I know the solenoid was replaced (with a new) just before I bought the car. Hmm...

Anyone that have an opinion on this? Should I send it away for OD renovation?

... My last life line, that still might be cheap to fix, is if it is a short circuit somewhere.

/Danne
 
Last edited:

Healey 100

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I certainly wouldn't send off the OD for rebuild without first driving the car with the tranny tunnel removed and activating the OD manually with the lever. If the lever is stuck, as suggested by your mechanic, you'll know that for sure. BTW, This is very unlikely because all the lever does is lift a tiny ball in the hydraulic system, not obvious what could cause it to get stuck, especially since the OD unit works intermittently now.

The OD linkage needs to be set up so that the solenoid contacts open when the OD is fully engaged -- this switches the solenoid over to the lower current holding coils. No doubt, if the contacts don't open for any reason, the solenoid and its wiring could burn up, that pull in coil is designed to just be activated for an instant to pull the OD lever into engagement.

I think the only decent way to diagnose an OD problem is with the tunnel off so you can engage the OD by hand, adjust the linkage, see what the solenoid is doing and even measure the pump pressure in the unit. Sorry this is relatively difficult with a BJ8, but it is nothing compared to rebuilding an OD. These OD's are very tough, they rarely seem to need rebuilding, even though they are fairly complicated.

Good hunting!
 

Gearhead_Garage

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The solenoid has two coils (spools), a high current one to initiate the overdrive engagement and a lower current one to hold it on. A set of points causes one to engage and the other to disengage. If the high current one does not disengage, you are correct, it will fry your wiring.

This definitely sounds electrical or adjustment related. Two things could cause the main coil not to disengage, 1. if it does not have full travel it will keep trying, 2. if the points are dirty, corroded, fused, etc. they will not operate correctly.

Full travel could be an adjustment or a bad solenoid. Bad points might be fixable with some disassembly. The symptom of weather affecting the operation points to points.
 
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Danne

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Thank you for your insightful posts. Since I don't know how to fix this myself, I have forwarded your posts to the mechanic and he found them very helpful in searching for the cause.

Another thought I have; from your thoughts on this it seems that the power and resistance are pretty important for the OD to work correctly. Since the OD-relay and throttle switch are bypassed now, can that mess it up?

Danne
 

Gearhead_Garage

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You can safely bypass the throttle lockout and gear shift lockout. Just do not drive the car in reverse with overdrive engaged.
 
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Danne

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Oh... that was good to know...

But right now, the gear shift relay is still connected. So that should not be a problem for me? Only OD relay and Throttle switch is bypassed.
 
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Oh... that was good to know...

But right now, the gear shift relay is still connected. So that should not be a problem for me? Only OD relay and Throttle switch is bypassed.

Not sure, but I don't think it's a good idea to bypass the relay. It's there because the panel switch can't take the load, and that might be part of the problem. Always remember, the bean-counters at BMC wouldn't allow any 'extra' parts if they weren't absolutely necessary.

I had intermittent OD operation once, on the road in Canada. Took the relay apart and filed the points and put it back in; worked perfectly after that.
 
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Danne

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Latest update:

The mechanic has looked at the electrics. Its 20A when the power is switched on. The cables are fine. But now the solenoid is totally dead.

I don't know what kind of solenoid the seller put there before the car was delivered to me, but the owner of the company is known as a "horse dealer", so I would expect that it was a cheap one.


Ok, then a theory could look like this (please correct me if I'm not thinking clearly); the OD-relay and/or the throttle switch has once become defective. Therefore they did a cheap solution and bypassed them. This caused the OD to sometimes not engage, which has led to burnt OD-switches. That made him install the mechanism that turns on a diode light at the dash board (if diode not is lighting, don't flip the OD-switch to "on"). This might also explain why the center console (with the switches) isn't screwed together with the upper part (dashboard), he had to exchange OD-switch every once in a while.


So if I buy and install a new OD-relay, new throttle switch and a new quality Lucas solenoid, it might solve the problem.

This I suspect will incorporate removing the tunnel. Then it would be a good time to test the OD, as Bill suggested.


Very bad timing:( And almost all workshops are closed or has very few people working now in Sweden. My vacation starts tomorrow and I was planning to drive a lot with the car... bummer.
 
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Danne

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Here's a picture of the switch on the OD, that operates the diode on the dashboard.

attachment.php
 

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British_Recovery

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I would get rid of that switch that touches the arm. Then check the overdrive by moving the lever into position ( hole in end lines up with hole in case ). With the tunnel off, you can get at most things yourself BUT BE CAREFUL, as things are spinning! This is a purely mechanical way of determining the state of the overdrive.
Bob
 

Gearhead_Garage

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Latest update:

Ok, then a theory could look like this (please correct me if I'm not thinking clearly); the OD-relay and/or the throttle switch has once become defective. Therefore they did a cheap solution and bypassed them. This caused the OD to sometimes not engage, which has led to burnt OD-switches. That made him install the mechanism that turns on a diode light at the dash board (if diode not is lighting, don't flip the OD-switch to "on"). This might also explain why the center console (with the switches) isn't screwed together with the upper part (dashboard), he had to exchange OD-switch every once in a while.

So if I buy and install a new OD-relay, new throttle switch and a new quality Lucas solenoid, it might solve the problem.

I think you may have drilled down to the correct solution. It sure is tougher to diagnose problems when the previous owner has made it worse!

By "throttle switch" did you mean throttle position relay or dashboard switch? I think you probably need a dashboard switch but your throttle position relay may be working. You can test throttle position relay by applying 12V and ground to the relay (normally this happens when you turn on ignition but your wiring may be changed). Make sure the linkage is connected so that the lever goes up and down with the accelerator pedal movement. Check the output as you press the accelerator pedal down. The output should show 12V at about 30% pedal travel. IMO, bypassing the throttle position relay would be fine since Triumphs were shipped without one.
 

Healey 100

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Danne:

20A sounds way high for a properly wired OD circuit. I think you are on the right track looking for a new solenoid and relay. Wire it like the shop manual says. If the linkage from the solenoid is adjusted correctly, the solenoid will engage on the high current coils for just an instant. Once the OD engages, the holding current needed to keep the OD engaged should be just a few amps. All this can be tested and observed with the tunnel removed -- including manual engagement of the OD with the lever. That is a way to bypass all the electrical systems to see if the OD unit is OK mechanically.

If the system is wired as per the manual, the throttle switch is probably the least important component of the OD control. All it does is prevent disengagement of the OD without first having a little opening of the throttle. This will smooth out the jolt when the system disengages (downshifts). Some think this switch is a kick-down switch, but it really will not kick down the OD unless the panel switch is turned off.

Your extra LED monitor is really not necessary if the unit is set up and wired as per the manual. The factory setup is really quite reliable and should work properly for years.

I don't think Lucas still makes the solenoids, but I believe there are decent repro units available. I have one I bought from Moss but I can't confirm if it is any good -- I just carry it with me as a spare that fortunately I have not yet needed! But it looks like a well made unit.

Bill.
 
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