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100 BN-1 Overdrive malfunction

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HEALEYJAG

HEALEYJAG

Jedi Warrior
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Here are the symptoms: Overdrive functions properly at 45-50 MPH. Goes right into lower gear without hesitation.

At higher speeds the overdrive goes on and off while at speed. If it disengages it will always engage again after flipping the switch off, then on again, then will disengage after 5-10 seconds.

I have always done my own work over the last 20 years, but at this time it is at a reputable sports car shop here in Columbus.

I felt that it was electrical because of the symptoms. They say all relays etc are fine, and feel it is internal.

This is the car that blew its freeze plug on its inaugural drive. The head gasket blew.

I still feel it is electrical and am contemplating pulling the car from the shop.

I would GREATLY appreciate any expertise in this area. This is my first Healey (out of 20) that has had overdrive issues.

Pete
 
Hello Peter,

if you would like to eliminate the electrical circuit, you could wire a simple on\off switch directly to the overdrive solenoid. You need to be very careful not to leave the overdrive selected when you stop as the danger of forgetting and then reversing could destroy it.

The second check if that still gives the same symptom is to check the solenoid pull in setting. I have always used the 3\16" dia hole in the arm on the opposite side of the case to the solenoid. I know others have a more sophisticated check, but I have found this works OK for me.

I'm forgetting to mention simple checks like oil level and that the oil filter is clean?

Alec
 
On my BJ8 the solenoid was the culprit, causing intermitent failures. The replacement was about $80. Wish I had changed it the first time I had the tunnel off.
 
Thankyou:

I will put a new solenoid on (if it is not new already), and check the oil filter of the overdrive. Everything else checks out OK.... Will let you know what the ANSWER IS..


Pete
 
I had the same problem with my BJ8, now fixed and was easy. The fault was the pressure valve on the right hand side of the overdrive unit, I just took out the spring and small shaft also the ball bearing. It was all cleaned thoroughly and replaced, took it out for a test run and all was fine. I think it might have been a a small blockage or the valve had got stuck in the off position. Whatever it was all is now working.
Brian
 
Pete, there are a few things you can do before you drain the fluid and "go inside". You can eliminate the solenoid by disconnecting the driveshaft(remove the bolts from the transmission flange) and run it that way so you don't have to go anywhere or jack the rear wheels. Just don't get your necktie in the spinning flange. Just move the lever by hand to see if you have the same problem. Remember if you are disconnecting the driveshaft, you will keep the RPM constant and see changes in speed read-out. If it still does the intermittant thing at higher revs then: 1. Fluid topped off. 2. I would next put a pressure gage in place of the operating valve cap. A glycerine filled gage 0-600psi (about 20 bucks at Grainger), you need an operating valve cap (so you can put the normal ball,spring, and guide pin in) you can modify by drilling a small hole in the top and welding a pipe coupling to it to accept the gage. I would assume the shop has this set-up if they work on Laycock overdrives. This will rule out some very insidious hydraulic problems like an oil pump that is sticking. You should have 350 to 475 psi out of the unit when OD disengaged. It should maintain that pressure except for momentary fluctuations when going into and out of overdrive. 3. If the pressure is good, or you want to skip item #2, then pull the operating valve piston out, make sure the bleed hole in it is clear and that the ball bearing and seat machined into the case is in good shape. Also check the seat on the tip of the operating valve piston where the ball sits when the solenoid engages.
4. Check for proper lift of the operating valve per the shop manual (or by measuring actual lift with a dial indicator (.020 works for me). Also make sure the solenoid is strong enough to overcome your fingers trying to hold it down when you engage it. It should be that strong. By all means check the archives for the numerous threads complete with diagrams and most possible problems. Let us know how it goes. Last, doesn't the BN-1 style overdrive have a speed sensing deal in it that is in place of the throttle switch? I'm not familiar with what, if any, quirks that part of the OD might have.

Jon
 
Thank you very much for your responses. I have made a copy of the "trouble shooting guidelines" listed earlier in the Forum from the Triumph club. I will be stopping by on wednesday to check on the progress.

Due to the intermittant nature of the problem I am convinced it is a hydraulic pressure issue relating to

1. malfunctioning pull-in coil in the solenoid

2. operating pressure valve sealing problem

3. improper lift of the operating valve

wish me luck!!

Pete
 
THE ANSWER IS>>>>


The points in one of the relays was opening and closing due to (dirt, old, lucas,rust, pick your choice). The intermittant connection cuased the solemoid to kick on and off.

Moral to the story..its USUALLY electric.

Pete
 
I am having similar problems with the O/D on my BN1, however the O/D does not last the ten seconds, it turns right on when the switch is flipped, then pretty much cycles in and out, seems to be dependent on the torque being applied to it, I can still get it to hold under no load, but add load either from a hill or throttle and it pops out.

I have the tunnel off and have observed operation both with the car off in the garage and driving.

Car parked, flip switch, car in top gear, bypass centrifugal switch (BN1 only device prevents low speed accuation of the O/D) and the accuating lever turns it right on. I tried prying it back (the external lever) with my fingers and could not do it.

Went for a drive--the solenoid/lever pops in and out as does the overdrive, voltage test at the solenoid was about 14 volts when on, drops down to 2-6 while cycling out.

I have

1. Checked and cleaned the relays off the car, they seem to be working fine.

2. Checked the operating valve, it was in spot on, changed the settings just a little to see if it ouwld make any difference, didn't help, set back to spec.

3. Checked the little ball thingy, no dirt clogging or interfering with operation there.

4. Bypassed the gear switch, didn't make any difference.

I am thinking bad solenoid, but it am puzzled that it seems to be working fine when the car is not running and also seemed to do what it was supposed to when off the car (attract and holds the plunger.)

Stumped I am, should I just pony up for a new solenoid and see if it works?? Or are there other tests I should try--maybe bypass the relays, haven't checked the throttle switch either, but not sure if that piece could cause the problem.
 
Glemon:

Go back to a previous post on overdrives, there will be a linkage to th Triumph club troubleshooting guide for overdrives. It will go step by step on the issue. Your problem is electric and could be the points in the solenoid.

Pete
 
One way to isolate if the failure is electrical(solenoid) is using an amp draw test. What you are doing is measuring the electrical charge used by the circuit(I recommend measuring as close to the solenoid as possible) You should get an initial amperage reading that peaks, then stabilizes. If the amperage climbs or drops then you know the problem is electrical in nature.

You've already given us the info that you have good voltage to the solenoid, so you are aware of the "mechanics" of electricity.

I frequently run into technicians in the field who want to replace a fuel pump motor, door solenoid, window motor, etc. because the customer states it doesn't work sometimes.


I ask them if they have performed an amp draw test. Mostly I am met with the "deer in the headlights" look until I explain to the tech that if they perform an amp draw test it is a very good indicator of problems occurring before failure. Every tech I have visited after the "amp draw" incident has thanked me for turning them on to a new troubleshooting tool, except one; and he isn't really a tech, just a parts changer.
 
O ROn you probably have given me too much credit for knowledge of electricity, with an amp test the solenoid draws about 1.25 amps then settles down to a steady draw of about one amp. I think this is consistent with what I read somewhere.

Getting back the th simple big hammer electronics troubleshooting methods, I hard-wired the solenoid and overdrive worked fine--so it would seem internal hydraulics and the solenoid are out.

Two tests showed something odd, the throttle switch would only close (on my ohmmeter) with one of the wires to it disconnected--or with relay R@ disconnected.

The book test on relay R2 is to test voltage across c1-c2 with the car in gear, then then short circuit C1-C2 on R1 and solenoid should operate and and voltage drop to zero on R2, I get no voltage drop on R2.

However, testing the thing (Relay R2) off the car it seems to do what is supposed to and has no shorts according to my Ohmmeter.

I had a spare relay that was good that I sold on E-bay a month or two ago for vbery little money, knew I should have kept it.

Anyway, think it it a relay for mine too, but the odd operation of the throttle switch and the fact that I cant find a short in the relay makes me wonder if there is a short in my wiring somewhere. I guess I'll go test that as best I can next.

Thanks for the help so far.

Greg
 
Rather than a short, sounds like a break in the wire, an open. Short would wind up blowing fuses or burning wires.

could be loose or corroded connection.
 
AND THE ANSWER IS (Part Deux):

After Much Head Scratching, Testing, Reading Manuals, Reading Internet Guides, Cleaning contacts and connections:

The Connection from the manual (main off on switch) to ground!

I got so caught up in thinking there might be something wrong with a relay, solenoid, throttle switch, lastly starting focusing on the throttle switch, because it seemed like the kicking in and out of O/D was somewhat dependent on throttle opening.

Cleaned the contacts and adjusted the throttle switch, no improvement.

Decided to read and think. Wiring diagram showed the main switch goes to ground on one side, decided to give that a closer look.

Connection was loose, it worked fine sitting there (each of the many times I did a stationary test) so I thought the switch and connections were fine. But with the car in motion the vibration made the connection intermittent.

Would have been nice if I would have figured it out before I took the tunnel off, oh well, I needed to seal the tunnel up better, which I have done.

Thanks for the advice and help.

Ron you got it right, loose connection
 
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