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Speedo problem BT7 - cable rotates but speedo does not
- Thread starter fishyboy
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Re: Sppedo problem BT7 - cable rotates but speedo does not
My Tach would go to 2700 rpm then fall off to zero and has been now going to 3300 rpm before falling off. Another issue and no solution. Same pertronix as before car dismantle so another issue.
My odometer moves but not the speedo cable. I was able to grab the cable under the dash when driving and move it around a bit about where it starts to curve from the transmission to a straight shot to the back of the speedo housing and I was able to get the needle to read. It was working finw before the frame-up restoration began. I have two speedos and both behave the same. I have a Toyota trans and the cable end sticks out of the cable housing about 3/8" which was originally slightly longer until I trimmed it thinking that that may be the problem. I was thinking that the cable itself could be at a slight angle going into the speedo housing causing the magnets to be off. The knurled nut is supposed to only be handtight. Who knows?
My Tach would go to 2700 rpm then fall off to zero and has been now going to 3300 rpm before falling off. Another issue and no solution. Same pertronix as before car dismantle so another issue.
RAC68
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Isn't wonderful how our Healeys keep our minds active?
Patrick, Check your tachometer connections at the coil. Are you getting any brief ignition firing issues when during the drop-off. It could be signaling an impending coil failure.
Phil, the speedometer needle is not directly connected to the drive cable or odometer. The cable drives a rectangular magnet that spins within the confines of a vertically-mounted metal pan that is connected to the needle and constrained by a very fine return spring. As the magnet is driven to spin, it induces movement of the pan and overcomes the spring. The needle should register (after calibration) as long as the magnet is spinning and inducing a sufficient force on the disk beyond the return springs counter force.
The problem: The drill is spinning the cable with sufficient speed to induce a needle reading and the transmission is not. I had this problem and it was caused by a short cable that, as other have mentioned, is worn at the tips and catches and releases and catches and releases. I also have experienced this in the action from a faulty angle drive. Although everything is new, I have had to returned 2 consecutively-delivered cables with slightly undersized tips that would appear to be turning sufficiently when not connected and not turn or produce needle movement when connected. Although you have viewed the movement of the cable and odometer by taking the back off the speedometer, I would suspect the cable may not have driven the magnet fast enough to induce needle movement. Also, I would suspect if when buttoned up and installed in the dash, the cable would be even slower.
If I remember correctly, I believe in the past a few of our posters indicated having a longer cable made up and bypassing the angle drive entirely with great success.
Again, I am hypothesizing based upon suspicions,
Good luck,
Ray (64BJ8P1)
Patrick, Check your tachometer connections at the coil. Are you getting any brief ignition firing issues when during the drop-off. It could be signaling an impending coil failure.
Phil, the speedometer needle is not directly connected to the drive cable or odometer. The cable drives a rectangular magnet that spins within the confines of a vertically-mounted metal pan that is connected to the needle and constrained by a very fine return spring. As the magnet is driven to spin, it induces movement of the pan and overcomes the spring. The needle should register (after calibration) as long as the magnet is spinning and inducing a sufficient force on the disk beyond the return springs counter force.
The problem: The drill is spinning the cable with sufficient speed to induce a needle reading and the transmission is not. I had this problem and it was caused by a short cable that, as other have mentioned, is worn at the tips and catches and releases and catches and releases. I also have experienced this in the action from a faulty angle drive. Although everything is new, I have had to returned 2 consecutively-delivered cables with slightly undersized tips that would appear to be turning sufficiently when not connected and not turn or produce needle movement when connected. Although you have viewed the movement of the cable and odometer by taking the back off the speedometer, I would suspect the cable may not have driven the magnet fast enough to induce needle movement. Also, I would suspect if when buttoned up and installed in the dash, the cable would be even slower.
If I remember correctly, I believe in the past a few of our posters indicated having a longer cable made up and bypassing the angle drive entirely with great success.
Again, I am hypothesizing based upon suspicions,
Good luck,
Ray (64BJ8P1)
Last edited:
I had a similar problem last week, after changing the speedometer cable, this left work, because it had assumed the angel drive.
As i do not believe in coincidences took the odometer have I tried to put the wire temporarily to move it by hand but it offered too much resistance
.I had not never disassembled an odometer but with the help of this manual, I couldn't do it without too much effort. In my case the problem was that when dismantling the old cable should move the dirt and it had blocked the rotation of the magnetic disk.
To mount it I had a second problem, I put too much grease in the gears and it was a film of oil between the plate and the magnetic flywheel, causing that the rotation of the cable move directly the speedometer needle, so I had to again remove the odometer to clean excess oil.It is a simple entertainment, mood.
Lorenzo
As i do not believe in coincidences took the odometer have I tried to put the wire temporarily to move it by hand but it offered too much resistance
.I had not never disassembled an odometer but with the help of this manual, I couldn't do it without too much effort. In my case the problem was that when dismantling the old cable should move the dirt and it had blocked the rotation of the magnetic disk.
To mount it I had a second problem, I put too much grease in the gears and it was a film of oil between the plate and the magnetic flywheel, causing that the rotation of the cable move directly the speedometer needle, so I had to again remove the odometer to clean excess oil.It is a simple entertainment, mood.
Lorenzo
Hi
Quick update.
I tried a new angle drive and connected the speedo. If you remember the speedo worked fine when connected to a drill, but not when on the car (with the back wheels jacked up). However, when I had the car jacked up I was only using first gear and I realized the speed was probably too low to get the sluggish speedo working. Putting the car in forth produced a slow movement of the speedo needle, but it was at least moving.
With the car on the road the needle worked but was still sluggish (slow to rise and fall), but at least it was working.
After about 10 miles the speedo stopped working. Removing the transmission tunnel revealed that yet another angle drive had broken.
I am now pointing the finger at the sppedo and it is in a box ready to be sent out for repair. A "working" broken speedo.
Phil
Quick update.
I tried a new angle drive and connected the speedo. If you remember the speedo worked fine when connected to a drill, but not when on the car (with the back wheels jacked up). However, when I had the car jacked up I was only using first gear and I realized the speed was probably too low to get the sluggish speedo working. Putting the car in forth produced a slow movement of the speedo needle, but it was at least moving.
With the car on the road the needle worked but was still sluggish (slow to rise and fall), but at least it was working.
After about 10 miles the speedo stopped working. Removing the transmission tunnel revealed that yet another angle drive had broken.
I am now pointing the finger at the sppedo and it is in a box ready to be sent out for repair. A "working" broken speedo.
Phil
Hi all,
Everything is now sorted (hopefully).
Speedo back from repairer (48 hour turn around). I can see the immediate difference as I can rotate the speedo needle by hand and it also move freely as I rotate the unit.
I checked out the speedo pinion which looked in excellent condition. However, I could not fit the pinion oil seal. it is far too big to go into the end of the end of the bearing so I left it off (there was not one on originally). I speak to the supplier tomorrow. Any ideas?
Connected up the new angle drive (with 3 copper washers - too many?) and connected cable to restored speedo.
On a quick test run all looks good with the speedo needle responding instantly.
Am I OK to leave the pinion oil seal off? Is three copper washers too many?
Phil
Everything is now sorted (hopefully).
Speedo back from repairer (48 hour turn around). I can see the immediate difference as I can rotate the speedo needle by hand and it also move freely as I rotate the unit.
I checked out the speedo pinion which looked in excellent condition. However, I could not fit the pinion oil seal. it is far too big to go into the end of the end of the bearing so I left it off (there was not one on originally). I speak to the supplier tomorrow. Any ideas?
Connected up the new angle drive (with 3 copper washers - too many?) and connected cable to restored speedo.
On a quick test run all looks good with the speedo needle responding instantly.
Am I OK to leave the pinion oil seal off? Is three copper washers too many?
Phil