Bob Birdsall Posted January 23 Report Share Posted January 23 My TR3a overdrive keeps jumping in and out of over drive when engaged or not engaged - any ideas? Thanks. Bob Quote Link to post Share on other sites
John Morrison Posted January 23 Report Share Posted January 23 Good Morning Bob. I have altered the title of your post to better 'Point' it at knowledgeable folk on here, jope thats alright? As regards your O/D issue, Oil level might be marginal, and that's your first check, or you could have a fault in the electrics, e.g. broken terminal, on an inhibitor switch, a wire,dashboard switch, need to take a look. John. Quote Link to post Share on other sites
RogerH Posted January 23 Report Share Posted January 23 Hi Bob, can we have more info. When it jumps in/out what gear is selected? Have you been working anywhere near the switch, wires, solenoid recently? When it jumps IN is the switch already in the IN position.? It could be more than one fault !!!! Roger Quote Link to post Share on other sites
ianc Posted January 23 Report Share Posted January 23 The solenoid has 2 coils: pull-in, which has thicker wires and takes greater current; hold-in, which has fine wire and takes a small current - see diagram D8-31 in the Technicalities CD. The hold-in coil can break at the soldered joint on the switch, with the result that the armature will drop down as soon as it lifts the contact. The pull-in coil then gets re-activated and the cycle is repeated. There will be a buzzing and, if left for very long, the solenoid will get cooked and fail. You can check without the engine running by selecting top gear, puitting the overdrive switch to "on", and trurning on the ignition. If all is well with the solenoid, there will just be a cluck, but if the hold-in coil is open circuit, a buzzzing will be heard - in which case, turn off the ignition! Ian Cornish Quote Link to post Share on other sites
RobH Posted January 23 Report Share Posted January 23 I read your post as meaning the OD will turn itself on and off randomly, whether or not you have it switched on. As the others have said, almost certainly it has to be something electrical. A fault in the OD switch is an obvious possibility. I guess this is an A type overdrive, in which case the solenoid is operated through a relay. The on/off switch and interlocks are on the coil side of the relay but the switching side (C1/C2) gets power all the time even though the OD switch is off, so it's possible a fault in the relay contacts might do that too. Quote Link to post Share on other sites
RogerH Posted January 23 Report Share Posted January 23 Does it happen when going over bumpy roads surface. The relay going mechanically soft. Roger Quote Link to post Share on other sites
Bob Birdsall Posted January 23 Author Report Share Posted January 23 13 hours ago, RogerH said: Does it happen when going over bumpy roads surface. The relay going mechanically soft. Roger It happens periodically on normal surfaces and is in/out of overdrive intermittently, I have tried putting a dab of light oil on the switch contact. Quote Link to post Share on other sites
Bob Birdsall Posted January 23 Author Report Share Posted January 23 13 hours ago, RobH said: I read your post as meaning the OD will turn itself on and off randomly, whether or not you have it switched on. As the others have said, almost certainly it has to be something electrical. A fault in the OD switch is an obvious possibility. I guess this is an A type overdrive, in which case the solenoid is operated through a relay. The on/off switch and interlocks are on the coil side of the relay but the switching side (C1/C2) gets power all the time even though the OD switch is off, so it's possible a fault in the relay contacts might do that too. Thanks, it happens when the overdrive is engaged, when for no apparent reason it will disengage then a while later re- engage Quote Link to post Share on other sites
Bob Birdsall Posted January 23 Author Report Share Posted January 23 14 hours ago, RogerH said: Hi Bob, can we have more info. When it jumps in/out what gear is selected? Have you been working anywhere near the switch, wires, solenoid recently? When it jumps IN is the switch already in the IN position.? It could be more than one fault !!!! Roger Thanks Roger, usually it jumps in and out in top gear when the overdrive is engaged, then it will for some reason, disengage overdrive and some time later re-engage it without touching the switch. I did put a dab of light oil on the switch terminal as I thought that may not be moving across properly, apart from that I haven't touched anything. Bob Quote Link to post Share on other sites
Bob Birdsall Posted January 24 Author Report Share Posted January 24 16 hours ago, John Morrison said: Good Morning Bob. I have altered the title of your post to better 'Point' it at knowledgeable folk on here, jope thats alright? As regards your O/D issue, Oil level might be marginal, and that's your first check, or you could have a fault in the electrics, e.g. broken terminal, on an inhibitor switch, a wire, dashboard switch, need to take a look. John. Thanks for the change John. I have checked most things without getting under the car, as the space underneath seems to be getting tighter each year! Quote Link to post Share on other sites
Bob Birdsall Posted January 24 Author Report Share Posted January 24 15 hours ago, ianc said: The solenoid has 2 coils: pull-in, which has thicker wires and takes greater current; hold-in, which has fine wire and takes a small current - see diagram D8-31 in the Technicalities CD. The hold-in coil can break at the soldered joint on the switch, with the result that the armature will drop down as soon as it lifts the contact. The pull-in coil then gets re-activated and the cycle is repeated. There will be a buzzing and, if left for very long, the solenoid will get cooked and fail. You can check without the engine running by selecting top gear, puitting the overdrive switch to "on", and trurning on the ignition. If all is well with the solenoid, there will just be a cluck, but if the hold-in coil is open circuit, a buzzzing will be heard - in which case, turn off the ignition! Ian Cornish Hi Ian, on your suggestion I have gone over it all again, the oil level is correct, wiring connectors OK, I opened up the switch and all moving internally there. When I tried it in top gear without the engine running and turned the ignition for the first time there was a clunk but when I tried it on subsequent time, no clunk, no buzzing -nothing. Quote Link to post Share on other sites
RogerH Posted January 24 Report Share Posted January 24 Hi Bob, it could be the 4rd/4th inhibit switch on the GB top cover. It may be that the fibre sealing washer needs to be thinned slightly to engage the sprung ball better. Failing that the operating shaft attached to the solenoid needs resetting. If the alignment holes is spot on then rotate it a fraction clockwise. Roger Quote Link to post Share on other sites
Lebro Posted January 24 Report Share Posted January 24 (edited) Right, having taken in all above comments, it is most likely electrical. Repeat above test (engine off), ignition on, overdrive selected. Start in neutral, then engage second gear, you should hear a click from the solenoid, repeat changing from neutral to 2nd several times, you should hear a click every time you engage the gear. Then try the same in top gear. if it misbehaves, try moving the gear lever small amounts while in top, does it click randomly. If so then the problem is the 3rd / 4th gear isolator switch, needing adjustment. If it misbehaves in 2nd gear as well, then problem is elswhere, check security of all the wiring passing between the switch, the relay, the solenoid, & the isolation switches. Bob Edited January 24 by Lebro Quote Link to post Share on other sites
Bob Birdsall Posted January 25 Author Report Share Posted January 25 17 hours ago, Lebro said: Right, having taken in all above comments, it is most likely electrical. Repeat above test (engine off), ignition on, overdrive selected. Start in neutral, then engage second gear, you should hear a click from the solenoid, repeat changing from neutral to 2nd several times, you should hear a click every time you engage the gear. Then try the same in top gear. if it misbehaves, try moving the gear lever small amounts while in top, does it click randomly. If so then the problem is the 3rd / 4th gear isolator switch, needing adjustment. If it misbehaves in 2nd gear as well, then problem is elsewhere, check security of all the wiring passing between the switch, the relay, the solenoid, & the isolation switches. Bob Thanks for that, I have been through all the gears in overdrive as you suggested but cannot get a click or sound from the solenoid in any gear when the overdrive is engaged also double checked the connections under the dash, I have opened up the switch and the components move freely. Unfortunately I don't have a hoist and doubt that I could see anything around the Solenoid without taking the bell housing cover off. Bob Quote Link to post Share on other sites
Lebro Posted January 25 Report Share Posted January 25 OK, next step will need a voltmeter, to check that you have volts present on the relay, & that you have continuity from earth (car chassis) through the gearbox switch(s) and through the on off O/D switch.(Follow the diagram above). Also you should be able to measure 12V on the relay output (C2) when all is switched on & in gear. It could be a relay failure. Try shorting C1 & C2 together that should definaely engage the solenoid, & you should here the click. if still nothing them maybe the solenoid is dead, but it would be unusual for it to be only dead sometimes !! Bob Quote Link to post Share on other sites
Bob Birdsall Posted January 26 Author Report Share Posted January 26 16 hours ago, Lebro said: OK, next step will need a voltmeter, to check that you have volts present on the relay, & that you have continuity from earth (car chassis) through the gearbox switch(s) and through the on off O/D switch.(Follow the diagram above). Also you should be able to measure 12V on the relay output (C2) when all is switched on & in gear. It could be a relay failure. Try shorting C1 & C2 together that should defintely engage the solenoid, & you should here the click. if still nothing them maybe the solenoid is dead, but it would be unusual for it to be only dead sometimes !! Bob Unfortunately I don't have a voltmeter but I have a friend coming to stay next week and will get him to bring one down as I'm a bit of a novice on electrics, where is the relay that I should check, do I need to take the bell housing cover off to get to it? When I move the overdrive switch up and down the amp meter does flicker so I sure that the is current from it. Bob Quote Link to post Share on other sites
Lebro Posted January 26 Report Share Posted January 26 Well that's encouraging. The relay should be attached to the bottom of the battery box, under the dash & above the gearbox cover. This assumes you have an "A" type overdrive. (which it should be) if, for some reason you have a "J" type fitted, then there wont be a relay. Relay looks like this, (if original fitting) click on to enlarge Bob Quote Link to post Share on other sites
Bob Birdsall Posted January 27 Author Report Share Posted January 27 20 hours ago, Lebro said: Well that's encouraging. The relay should be attached to the bottom of the battery box, under the dash & above the gearbox cover. This assumes you have an "A" type overdrive. (which it should be) if, for some reason you have a "J" type fitted, then there wont be a relay. Relay looks like this, (if original fitting) click on to enlarge Bob That's weird, I have just been underneath the dash and can't see the relay anywhere under the battery box or any holes where it should have been or anything else that look like it, I have traced the overdrive wires to the amp meter. Under the bonnet there is only the regulator and the fuse box that control's electrics. In your photo it shows it exposed and easily seen so I must be missing something. Yes it is an "A" type overdrive added about 15 years ago. I really appreciate your help on this as there are very few Side Screen TR's in New Zealand and even less people, including mechanics, that know anything about fixing them. The last mechanic forced my handbrake off not knowing it was quick release and it took me ages to work out how to fix it. Bob Quote Link to post Share on other sites
Ian Vincent Posted January 27 Report Share Posted January 27 Have you traced the wires from the switch? Where do they go? If you look at Rob’s post at the top of this thread, the switch connects to the relay. Rgds Ian Quote Link to post Share on other sites
BlueTR3A-5EKT Posted January 27 Report Share Posted January 27 There is the chance that the overdrive was wired in without a relay. Like a J type is. The Atype needs a relay in its circuit to protect the operating and isolating switches from the high current required to operate the operating solenoid. Try this. Ignition off. Disconnect the two two wires from the overdrive switch and keep them from touching anything or each other. Turn on the ignition and engage 2/3 or 4 th gear Engine not started. Now touch the ends of the two switch wires together Is there a click or other noise? In which case your dash switch is failing.. with the two wires connected engage different gears, 2/3/4. Does the noise happen still? Turn off ignition, refit wires to switch. If you cannot find the relay Start from scratch and fit a full relay operated wiring system for the overdrive. Ready made looms are available new as is the relay Given a wiring diagram it is not a big deal to make your own loom from cable and end fittings. Quote Link to post Share on other sites
RogerH Posted January 27 Report Share Posted January 27 Interesting. I never thought it would be difficult to find the relay but a PO could put it anywhere. The J type OD Logic box that I make and sell has this relay fitted into the box as the circuit needs feedback from the relay to work. So my 'A' type Logic boxes are built just the same as of this year. So you wire from switch to Logic box to Solenoid - No 6RA to get lost. Roger Quote Link to post Share on other sites
RobH Posted January 27 Report Share Posted January 27 (edited) It seems to me that the original fault is in danger of becoming a bit lost here. Now we know the symptoms are intermittent dropping-out when OD is switched on, and if it only happens in 4th gear, the obvious suspect is the interlock switch adjustment as Roger and Bob L have already said. Anything else - electrical or mechanical - would surely affect 2nd OD or 3rd OD as well. Even the wiring and the interlock switch itself are shared with 3rd gear, so must be OK if that is unaffected. ( Bob B -the same interlock switch is used for both 3rd and 4th gear and is operated by detents on the 3rd/4th selector rod in the gearbox remote. The depth of insertion of the switch can be adjusted so that both gear positions switch reliably. Wear can mean the switch action becomes unreliable in one or both positions and re-adjustment can cure this.) The transmission tunnel will have to come off for access to that and I don't think you can really trace the wiring properly any other way as well - who knows, the relay may have been put down there too. If there is no relay, that is a separate issue and is obviously something that needs sorting for the longevity of the OD switch, but it doesn't affect just 4th OD so probably isn't pertinent to the fault itself. Edited January 27 by RobH Quote Link to post Share on other sites
Lebro Posted January 27 Report Share Posted January 27 +1 Bob Quote Link to post Share on other sites
Hamish Posted January 27 Report Share Posted January 27 Have we checked the gear lever gator. I think there have been problems reported in the past with the gator just holding the lever enough to affect the switches intermittently Quote Link to post Share on other sites
RobH Posted January 27 Report Share Posted January 27 Well remembered Hamish - though I hope the stick doesn't have a 'gator but rather a gaiter. Gator: https://www.uglyhedgehog.com/t-742245-1.html (sorry - couldn't resist) Quote Link to post Share on other sites
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