stepper motor change help please
Discussion
Any advice gratefully received!
My Mk 1 Tuscan heater stepper motor has given up and I arrive everywhere shivering and with white fingers. It can open but not close the flap. I've ordered a new one but need advice about how to change it. It looks as though the motor is riveted to a bracket but I can't see how the arm is attached to the motor nor how the arm is attached to the flap. What's the least fiddly way to replace the motor without swearing and boot imprints in the body panels?
Advice for the mechanically challenged please
Thanks
My Mk 1 Tuscan heater stepper motor has given up and I arrive everywhere shivering and with white fingers. It can open but not close the flap. I've ordered a new one but need advice about how to change it. It looks as though the motor is riveted to a bracket but I can't see how the arm is attached to the motor nor how the arm is attached to the flap. What's the least fiddly way to replace the motor without swearing and boot imprints in the body panels?
Advice for the mechanically challenged please
Thanks
Remove windscreen scuttle
Remove Lambda wires and plugs cable ties onto heater water pipes
Unscrew the 4 screws holding the heater box down and a bit of brute force will see it come out. You don't need to remove the hoses as there's enough slack in them.
Once the box is off the stepper motor is in plain sight.
The arm is attached to the stepper motor with a grub screw. This often becomes loose causing the heater not to work and the motor is fine. I wonder how many garages charge for a replacement motor when in fact all they've done is tighten the grub screw up
The linkage is attached to the arm and door with some simple clips.
The motor bracket is attached to the car with some captive nuts and comes out easily.
Refitting is the reverse of the above.
One thing that's obvious is that the full travel of the stepper from full cold to full hot is approx 180deg. When attached to the door, it only allows about 60deg of motion so the motor not only stalls but you have terrible control "resolution" and is alreday on full hot when the 3rd LED on the heater control knob is lit.
I modded my linkage to accomodate the full travel of the stepper and consequently gain far better cabin temperature control. I basically drilled a new linkage position on the arm closer to the output shaft and fabricated my own revised linkage rod to accomodate the new likage geometry.
Sounds tricky but its very simple, works much better and also saves the motor. Baffled as to why TVR designed it this way as its plain to see that its simply crap and doesn't work properly.
Remove Lambda wires and plugs cable ties onto heater water pipes
Unscrew the 4 screws holding the heater box down and a bit of brute force will see it come out. You don't need to remove the hoses as there's enough slack in them.
Once the box is off the stepper motor is in plain sight.
The arm is attached to the stepper motor with a grub screw. This often becomes loose causing the heater not to work and the motor is fine. I wonder how many garages charge for a replacement motor when in fact all they've done is tighten the grub screw up
The linkage is attached to the arm and door with some simple clips.
The motor bracket is attached to the car with some captive nuts and comes out easily.
Refitting is the reverse of the above.
One thing that's obvious is that the full travel of the stepper from full cold to full hot is approx 180deg. When attached to the door, it only allows about 60deg of motion so the motor not only stalls but you have terrible control "resolution" and is alreday on full hot when the 3rd LED on the heater control knob is lit.
I modded my linkage to accomodate the full travel of the stepper and consequently gain far better cabin temperature control. I basically drilled a new linkage position on the arm closer to the output shaft and fabricated my own revised linkage rod to accomodate the new likage geometry.
Sounds tricky but its very simple, works much better and also saves the motor. Baffled as to why TVR designed it this way as its plain to see that its simply crap and doesn't work properly.
dvs_dave said:
The arm is attached to the stepper motor with a grub screw. This often becomes loose causing the heater not to work and the motor is fine. I wonder how many garages charge for a replacement motor when in fact all they've done is tighten the grub screw up
ive had this done to me by a garage, i know this as 6 months later it really did burn out and was changed by a different, much better specialist, and had it been changed as charged for the wires would have been different colours, thanks a bunch fer
t
dvs_dave said:
I modded my linkage to accomodate the full travel of the stepper and consequently gain far better cabin temperature control. I basically drilled a new linkage position on the arm closer to the output shaft and fabricated my own revised linkage rod to accomodate the new likage geometry.
Dave,Any pictures of the new linkage position and modified linkage rod by any chance?
The cover isn't actaully fixed to the bulkhead. It's attached to a rubber elbow under the dash (there's one for hot, and another for cold) with a bit of black silicone. Once the 4 screws are off, just work it loose with a bit of brute force. It will come and it won't damage anything.
The clonk you get is the two non-return air flaps inside the dashboard moulding. The whole dash moulding is hollow and acts as a plenum to mix the hot/cold air and then distribute it around the car. This part is actually well designed! Anyway when you switch the ignition on, the fan gives a little puff which blows these flaps open and they clonk on the inside of the dash and then close under their own weight. I fixed mine by taking the dash out (two bolts at either side that are a bit tricky to get to) and sticking felt pads on the flap "impact" areas inside the dash. No more clonks.
Anyway, couple of pics of my car with the airbox out and some close-ups of the stepper motor/blend door arrangement.
I can't find a pic of the modded stepper motor arm (I'm sure I took one?!?!?) but all I did was drill a new hole in the arm closer to the output shaft, made a longer linkage arm (bit of bent 4mm ally rod) and moved the linkage into to the arm in the newly drilled pivot position.
I had to shorten the arm length to allow it to rotate all the way round without fouling the base. You have to make sure the full cold position of the flap actually stops the stepper arm rotating any further anti-clockwise. Reason being that whenever the ignition is switched on, the stepper motor is commanded to rotate anti-clockwise for 10 seconds or so to find it's "zero point" (stalling in the process). It then rotates to the position as commanded by the heater control knob. If you get the linkage length wrong the stepper can rotate freely all the way round causing the linkage/flap to go out of phase. I determined the best rod length by trial and error.
It's actually a fairly good system apart from this completely wrong linkage geometry, or more likely a wrongly specified stepper motor. In which case the system would be fine if the "steps" were smaller.
The clonk you get is the two non-return air flaps inside the dashboard moulding. The whole dash moulding is hollow and acts as a plenum to mix the hot/cold air and then distribute it around the car. This part is actually well designed! Anyway when you switch the ignition on, the fan gives a little puff which blows these flaps open and they clonk on the inside of the dash and then close under their own weight. I fixed mine by taking the dash out (two bolts at either side that are a bit tricky to get to) and sticking felt pads on the flap "impact" areas inside the dash. No more clonks.
Anyway, couple of pics of my car with the airbox out and some close-ups of the stepper motor/blend door arrangement.
I can't find a pic of the modded stepper motor arm (I'm sure I took one?!?!?) but all I did was drill a new hole in the arm closer to the output shaft, made a longer linkage arm (bit of bent 4mm ally rod) and moved the linkage into to the arm in the newly drilled pivot position.
I had to shorten the arm length to allow it to rotate all the way round without fouling the base. You have to make sure the full cold position of the flap actually stops the stepper arm rotating any further anti-clockwise. Reason being that whenever the ignition is switched on, the stepper motor is commanded to rotate anti-clockwise for 10 seconds or so to find it's "zero point" (stalling in the process). It then rotates to the position as commanded by the heater control knob. If you get the linkage length wrong the stepper can rotate freely all the way round causing the linkage/flap to go out of phase. I determined the best rod length by trial and error.
It's actually a fairly good system apart from this completely wrong linkage geometry, or more likely a wrongly specified stepper motor. In which case the system would be fine if the "steps" were smaller.
Edited by dvs_dave on Monday 14th February 17:33
So does it fix the anoying clonk-clonk-clonk noise. I'd assumed that was where the flap was fully closed and the motor was still trying to push it shut, and hence slipping or stalling or something ? But from your description it sounds like this will still happen because the flap has to close as part of the zeroing procedure that the software uses to know where "closed" is.
Folks,
I've just had to replace/re-core the heater matrix on my Mk.1 's'.
I followed Dave's instructions as above but obviously removed the heater in & out pipes.
I've cured the coolant loss issue, but the airflow out of the vents is not particularly good.
I believe I did a more thorough job on 'masticing in' the matrix into the heater box than the factory did. Could this be a possible cause - with all the air having to go through the matrix?
I did silicon the circular 'duct' into the bulkhead.
Any other thoughts from you guys. Motor is definitely running - - almost sounds louder - could I have disturbed something under the dash?
Thanks in antici0pation.
Nick
I've just had to replace/re-core the heater matrix on my Mk.1 's'.
I followed Dave's instructions as above but obviously removed the heater in & out pipes.
I've cured the coolant loss issue, but the airflow out of the vents is not particularly good.
I believe I did a more thorough job on 'masticing in' the matrix into the heater box than the factory did. Could this be a possible cause - with all the air having to go through the matrix?
I did silicon the circular 'duct' into the bulkhead.
Any other thoughts from you guys. Motor is definitely running - - almost sounds louder - could I have disturbed something under the dash?
Thanks in antici0pation.
Nick
nawarne said:
Folks,
I've just had to replace/re-core the heater matrix on my Mk.1 's'.
I followed Dave's instructions as above but obviously removed the heater in & out pipes.
I've cured the coolant loss issue, but the airflow out of the vents is not particularly good.
I believe I did a more thorough job on 'masticing in' the matrix into the heater box than the factory did. Could this be a possible cause - with all the air having to go through the matrix?
I did silicon the circular 'duct' into the bulkhead.
Any other thoughts from you guys. Motor is definitely running - - almost sounds louder - could I have disturbed something under the dash?
Thanks in antici0pation.
Nick
Where you silconed the duct to the bulkhead that duct also attaches to a hose the other side of the bulkhead. This hose feeds the top dash plenum and then in turn the vents. If this hose isn't connected, all you'll be doing is blowing air into the top of passenger footwell and the back of the lower dash. When you removed the box in the engine bay you would have removed the seal to the hose in the car so worth checking there.I've just had to replace/re-core the heater matrix on my Mk.1 's'.
I followed Dave's instructions as above but obviously removed the heater in & out pipes.
I've cured the coolant loss issue, but the airflow out of the vents is not particularly good.
I believe I did a more thorough job on 'masticing in' the matrix into the heater box than the factory did. Could this be a possible cause - with all the air having to go through the matrix?
I did silicon the circular 'duct' into the bulkhead.
Any other thoughts from you guys. Motor is definitely running - - almost sounds louder - could I have disturbed something under the dash?
Thanks in antici0pation.
Nick
There's a 3" rubber elbow that connects each airbox into the dash plenum. These are a firm push fit onto each airbox outlet and the dash. As said, if these aren't connected up, it'll just blow air into the area above the passenger footwell. Easiest way to tell if they're on properly is to set the fan on high and feel for drafts up behind the passenger side dash on full hot & cold.
Thanks for the replies gents.
The problem was down to a poor seal connection between the 'hard' grp duct from the heater box to the flexible elbow to the flapper/butterfly valve 'thingy' under the dash.
Some careful silicone use has restored a veritable torrent of hot air to windscreen and footwell vents.
Nick
The problem was down to a poor seal connection between the 'hard' grp duct from the heater box to the flexible elbow to the flapper/butterfly valve 'thingy' under the dash.
Some careful silicone use has restored a veritable torrent of hot air to windscreen and footwell vents.
Nick
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