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melted down my O/D harness on BN6

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bighealeysource

bighealeysource

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Hey all,
Well, solved my overheating problem, toe in problem and leaky
pinion seal problem, now got another new one ! During my
recent 50 mile test drive I went to use the O/D which has
been rebuilt but it didn't work. Figured it was probably
something simple as many electrical issues are with the O/D.
Wrong again, my O/D harness melted down obviously due to
some short somewhere. A friend of mine who knows his stuff
about electrical issues thinks the relay may have gone
bad as appears it melted first as power was attempting to go
from the switch through the relay. Thinks it might be the coil
inside. I think one can rebuild the relay as believe I have seen articles about that in the Healey Club USA magazine. Of
course if that is the problem. Any thoughts, advice, etc
from y'all out there in Healey land ?
Thanks,
Mike
 
Nope, it is the solenoid on the transmission. That requires a high amperage jolt to pull up the actuating lever then lowers to a low amperage draw to remain there. When the solenoid goes bad it sticks in the high amperage mode and burns up the harness. I know because the exact same thing happened to me a few years back. Solenoids are available at a reasonable cost from the English suppliers.
 
same thing's just happened to me on a brand new solenoid - from one of the 'english suppliers' you refer to (I'm in England)! I also had probs getting my freshly rebuilt OD to work (clutch was sticking) - not sure if this had anything to do with causing the solenoid problem. the wire that melted was the one from the inhibitor to the solenoid. filled the whole cockpit with that fabulous smell of frying electrical componentry so beloved of us British! my gearbox rebuilder is trying to find me an 'old' solenoid to try to prevent the problem happening again - I've returned the faulty one and if I don't get a refund and an apology I'll tell you who the supplier was!
 
I had the same thing happen to my overdrive harness in 1975. It was not the solenoid. It was the relay. Repaired the burnt wires and changed the relay and everything worked okay.

Also had a bad solenoid that didn't have enough power to "pull up" and engage the overdrive. It made a good clicking sound when I tried to egage it and that slowed down my troubleshooting process until I finally swapped out the solenoid.
Patrick
 
What timing!!!
I just finally diagnosed a similar problem while working out the inevitable bugs on a complete restoration of a '65 BJ8, and it wasn't the solenoid or the relay. It was the throttle switch. The switch lever had been off for cleaning and replating, etc. When initially replaced, the slotted shaft when viewed from the side was turned all the way clockwise, causing the cam inside to contact the nearest screw contact.....result....straight short to ground. It instantly caused a new relay to chatter and started melting the white/green wire between relay and throttle switch, all in about 3 seconds.
Cure was to carefully set the switch and the shaft correctly, and replace the o/d harness. Everything works perfectly now.
I followed up by bench testing 3 more throttle switches, and sure enough, if the shaft is turned all the way "up" clockwise, it reaches a point where the cam can touch the internal contact for the upper termainal, causing a dead short.
 
All good reasons to add a 10 amp fuse to your overdrive circuit. I installed the fuse and then put in a new solenoid but did not change the plunger. The new solenoid needed a slightly longer plunger and with the old (too short) one, the low amp circuit never engaged. It blew the fuse, but did not harm the wires. I figured out the problem and put in the new plunger. Everything works great now.
 
Thanks everyone for your advice on what to check out. I'll get into the
whole thing in a couple of weeks and then post a follow up on what it
actually turned out to be !
Regards,
Mike
 
Hey again on this subject,
Got my new O/D relay from AH Spares and want to take Tim's advice and put in
a 10 amp fuse on the O/D circuit. Where is the best place to install the fuse ?
BTW, when I took apart the old O/D relay, it was very heavily rusted inside.
I ordered the new one but will check out the old one before installing the
new one. The throttle relay was in good condition and closed it back up
after carefully touching up the points so believe it is good to go. Still
need to check the solenoid.
Thanks,
Mike
 
Want to take Tim's advice and put in
a 10 amp fuse on the O/D circuit. Where is the best place to install the fuse:

Mike. in a spot that you can easily replace it.

However, you do not need a 10 amp fuse a 5 amp will work just fine to prevent harness failure in the event of a short.

Logic:
If the falure blows a 10 amp fuse it certainly will blow a 5 amp faster.--Fwiw-Keoke
 
My Healey OD solenoid draws more than 10 amps when the solenoid is pulling in -- though it only draws it for a very short time. If I recall, the resistance of my pull-in coil is quite a bit less than 1 ohm. The holding coil resistance is much higher. If you use a fuse, get the slow-blow variety.

An improperly adjusted linkage on the OD can prevent the solenoid from moving far enough to open the contacts that switch to the holding coil. Staying connected to the pull-in coil could possibly lead to melted wires.....

Bill S
NM
 
If you use a fuse, get the slow-blow variety.

:iagree: Bill S,
That will add some more margin.However, the 5 amp fuse already has significant margin included for this circuit--Keoke :thumbsup:
 
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