-
Hi Guest!
If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
There are some perks with a member upgrade!**Upgrade Now**
(PS: Subscribers don't see this gawd-aweful banner
Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
STOP!! Never post your email address in open forums. Bots can "harvest" your email! If you must share your email use a Private Message or use the 
smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
TR2/3/3A Over drive
- Thread starter TRo8son1
- Start date
Share this page
TR3driver
Great Pumpkin - R.I.P
Offline
Yup, definitely a sign the contacts aren't opening. Could be the solenoid plunger not making it all the way (as in my case); or the pushrod melted/worn; or the contacts welded somehow. Probably lots of other things as well.
One danger that isn't especially well documented: it's important that the solenoid plunger not fall too far out of the solenoid. If it drops too far, even the "pull-in" coil may not be able to lift it against hydraulic pressure (and the coil being hot, etc).
The factory manual talks about a "drop" adjustment; but later ODs did not have that adjustment. Instead, they used a rubber stop, that tends to deteriorate and eventually fall out. For a long time, I didn't even realize there was supposed to be something there.
I modified the bracket, so I could fit a socket head screw for the stop, and used a flat washer under the head to adjust the drop.
One danger that isn't especially well documented: it's important that the solenoid plunger not fall too far out of the solenoid. If it drops too far, even the "pull-in" coil may not be able to lift it against hydraulic pressure (and the coil being hot, etc).
The factory manual talks about a "drop" adjustment; but later ODs did not have that adjustment. Instead, they used a rubber stop, that tends to deteriorate and eventually fall out. For a long time, I didn't even realize there was supposed to be something there.
I modified the bracket, so I could fit a socket head screw for the stop, and used a flat washer under the head to adjust the drop.
What is the black piece just above the narrow band on the plunger?
I will take my solenoid off the car in the morning to do some tests. I am sure the plunger is making it all the ay up because there is a small amount of travel possible left on the operator arm.
Under the rubber cover there is a white plastic cover with 2 tiny nuts I presume the switch is under there?
David
I will take my solenoid off the car in the morning to do some tests. I am sure the plunger is making it all the ay up because there is a small amount of travel possible left on the operator arm.
Under the rubber cover there is a white plastic cover with 2 tiny nuts I presume the switch is under there?
David
TR3driver
Great Pumpkin - R.I.P
Offline
That's a rubber boot, to help keep dirt and water out of the solenoid. Normally supplied with the solenoid, you can see a little better view here
http://trf.zeni.net/TR6-TR250GB/269.php
This is what the contacts look like, on that solenoid. The older one was similar. You can see part of the white cover to the left
http://trf.zeni.net/TR6-TR250GB/269.php
This is what the contacts look like, on that solenoid. The older one was similar. You can see part of the white cover to the left
Took the solenoid off the gearbox and checked the travel of the plunger and it did bottom out.
Removed the rubber cover and could see the whiteish cover was held with 2 nuts (Probable 6BA). Removed the nuts and cover. The plunger was working but not reaching high enough to open the contact. There was a lot of pressure on the contacts and I could see the fixed contact could be adjusted down. I did that and the contacts open now.
Back on the car I get about 1,5 amps when it is operated and a 10 amp fuses is holding so far. May try a 7.5 or 5 amp fuse.
David
Removed the rubber cover and could see the whiteish cover was held with 2 nuts (Probable 6BA). Removed the nuts and cover. The plunger was working but not reaching high enough to open the contact. There was a lot of pressure on the contacts and I could see the fixed contact could be adjusted down. I did that and the contacts open now.
Back on the car I get about 1,5 amps when it is operated and a 10 amp fuses is holding so far. May try a 7.5 or 5 amp fuse.
David
TR3driver
Great Pumpkin - R.I.P
Offline
Almost looks like there used to be a piece under the arm, where the pushrod hits it, that has gone AWOL.
You might want to see if you can get those contacts to meet more squarely. They switch a fair amount of current (with lots of inductive kickback), and a point contact doesn't create a lot of area to conduct the current. Might not matter, but that's what I would do.
You might want to see if you can get those contacts to meet more squarely. They switch a fair amount of current (with lots of inductive kickback), and a point contact doesn't create a lot of area to conduct the current. Might not matter, but that's what I would do.
The round mark on the arm is from what appears to be a rubber stop on the plastic cover.
I hesitate to try bending the contact too much. Would a contact file be better? Looking at the button I may be able to add a bit to that and return the fixed contact to its original position. Getting the button out may do more damage than it helps.
I do have a new one on the way so this one may become a spare.
I hesitate to try bending the contact too much. Would a contact file be better? Looking at the button I may be able to add a bit to that and return the fixed contact to its original position. Getting the button out may do more damage than it helps.
I do have a new one on the way so this one may become a spare.
I am running an alternator through the Ammeter (60 amp) wired up as the generator would have been. The OD solenoid supply comes from the fuse holder terminal "A1" via a separate dedicated fuse. I noticed that before I fixed the solenoid internal switch so the amp draw is reduced the ammeter would show a 20 amp charge when the engine was running and OD engaged.
The Ammeter is wired correctly as it shows a discharge if I turn the head lights on with the engine shut off.
I am presuming that the charge shown was because the high current draw by the OD solenoid before I corrected internal switch.
David
The Ammeter is wired correctly as it shows a discharge if I turn the head lights on with the engine shut off.
I am presuming that the charge shown was because the high current draw by the OD solenoid before I corrected internal switch.
David
TR3driver
Great Pumpkin - R.I.P
Offline
I'm not sure why the factory wired it that way, but they did. Since the solenoid is getting power from the battery side of the ammeter, the solenoid current shows up as a charge on the ammeter. Normal draw is too small to see, but the 20 amps for the pull-in coil certainly isn't.