Solution for the noise when turning on the ignition....
Discussion
It comes from the passenger side bulkhead and I understand it's something to do with the heater adjusting itself and happens on a lot of early MK 1s.
I remember seeing a solution for this somewhere but I cant for the life of me find it. It was as simple as adjusting one of the heater knobs after turning off the engine, but whatever I try isn't working!
Does anyone know?
Cheers.
I remember seeing a solution for this somewhere but I cant for the life of me find it. It was as simple as adjusting one of the heater knobs after turning off the engine, but whatever I try isn't working!
Does anyone know?
Cheers.
I think i know what you mean, is it as simple as pushing the heater airflow knob to turn the fans completely off. ie no lights on, then when the engine starts push the knob again and the fans are on with no noise. I know if i leave my ignition on then it makes a strange sound till i do this.
Rich
Rich
Night Rider said:
Very close, it's mounted on the main chassis rail LHS between the rear wheel and diff.
My car has a think that looks like a canister/fuel pump mounted on the roll hoop behind the speaker panel. Does anyone know what it is? Its black, about 7 inches long and 2 inches in diameter (no crude comments please 
) and appears to have tubes or cables going to it.I didnt look closely when I was doing the door locks, but did wonder what it is
I've just taken my heater ECU out and it's stopped the noise happening so I guess it must be the heater making the noise.
Out of curiosity, I took the ECU apart and everything looks nice and shiny, however the heater does work a bit intermitently so guess the ECU isn't as good as it should be.
Going to go fit it back in and see how it behaves now.
Out of curiosity, I took the ECU apart and everything looks nice and shiny, however the heater does work a bit intermitently so guess the ECU isn't as good as it should be.
Going to go fit it back in and see how it behaves now.
The noise you describe sounds like the heater stepper motor trying to through it's start cycle as it opens and closes the heater flaps. The nylon gears on these motors can strip causing this problem. There has been some topics on this in the past including a guide to changing the motor.
When you turn the ignition on, two things happen with the HVAC. The fan turns on with the ignition which gives a puff of air that blows open the non return air flaps inside the dash top. This is the clonk that you hear.
At the same time, the heater blend door stepper motor does a cycle to full cold to zero itself. It then returns to the position as set by the temp knob. This is the whirring that you hear as the gears strip and it becomes noisy as the motor doesn't have any travel limit switches on it. It's a good design made really crap by the heater ECU not having any travel limit control.
At the same time, the heater blend door stepper motor does a cycle to full cold to zero itself. It then returns to the position as set by the temp knob. This is the whirring that you hear as the gears strip and it becomes noisy as the motor doesn't have any travel limit switches on it. It's a good design made really crap by the heater ECU not having any travel limit control.
That's excellent information. Done so much searching and found nothing close to that, thanks
So say I have the temp knob positioned to as cold as possible when I turn on the ignition, should the stepper motor have no need to do its cold cycle seeing how it's on cold already? Because mine seems to want to.
I have also found I get second noise when the knob gets to the first red light which sounds more like grinding.
So say I have the temp knob positioned to as cold as possible when I turn on the ignition, should the stepper motor have no need to do its cold cycle seeing how it's on cold already? Because mine seems to want to.
I have also found I get second noise when the knob gets to the first red light which sounds more like grinding.
From my meddlings, the initialisation process involves the stepper motor being commanded to turn to the full cold position for what seems like 5-7 seconds, regardless of it's starting position. Once it's completed this cycle it then operates under the control of the temp control knob. It does this as there is no stepper motor position feed back loop.
So basically, what happens is that the stepper motor ends up stalling when it reaches the full cold position which over time ends up stripping the gears in it's little gearbox. This is what the grinding noise you're hearing is as it's reached it's limit of travel but the motor is still being commanded to turn. Basically you'll need a new stepper to sort it.
Another thing I found was that with the linkage removed, the travel of the stepper motor from full hot to full cold is about 180 degrees, with each step on the heater control knob corresponding to approximately 10-15deg rotation. The problem is that the heater blend door only allows it to travel a total of about 45 degrees from full hot to full cold, so it ends up stalling at both extremes of travel. This is why the temp control is so woeful and only does cold, hot, very hot.
I went on to modify the crank arm length and connecting rod on mine to stop this happening and to give much finer control of the cabin temp which has worked well. The cycle to full cold and motor stall cannot be stopped though.
Like I say, physically good design, but ruined by an unbelieveably crap and lazily excecuted control system. Anyone know how to modify the control box to rectify this?
So basically, what happens is that the stepper motor ends up stalling when it reaches the full cold position which over time ends up stripping the gears in it's little gearbox. This is what the grinding noise you're hearing is as it's reached it's limit of travel but the motor is still being commanded to turn. Basically you'll need a new stepper to sort it.
Another thing I found was that with the linkage removed, the travel of the stepper motor from full hot to full cold is about 180 degrees, with each step on the heater control knob corresponding to approximately 10-15deg rotation. The problem is that the heater blend door only allows it to travel a total of about 45 degrees from full hot to full cold, so it ends up stalling at both extremes of travel. This is why the temp control is so woeful and only does cold, hot, very hot.
I went on to modify the crank arm length and connecting rod on mine to stop this happening and to give much finer control of the cabin temp which has worked well. The cycle to full cold and motor stall cannot be stopped though.
Like I say, physically good design, but ruined by an unbelieveably crap and lazily excecuted control system. Anyone know how to modify the control box to rectify this?
Edited by dvs_dave on Thursday 6th October 21:02
Like I say, physically good design, but ruined by an unbelieveably crap and lazily excecuted control system. Anyone know how to modify the control box to rectify this?
Would need to build a new one unfortunately, the good news is that it wouldn't be that hard if we had some wiring diagrams! I used to run a company that could have done it at lunchtime (maybe 2)
The wiring diagrams of TVR black boxes never seem to have come to light in the public domain. But surely for those with the knowledge, taking one apart, tracing the circuits and components back and figuring it out wouldn't be hard?
If you were going to do this, then you could also figure out how to incorporate an automatic temperature and fan speed control system like a basic climate control system. All the components are there to make it work (bar the cabin temp sensor) so an upgraded control box that has these features would be a very nice thing to have.
How much would it cost to do this?
If you were going to do this, then you could also figure out how to incorporate an automatic temperature and fan speed control system like a basic climate control system. All the components are there to make it work (bar the cabin temp sensor) so an upgraded control box that has these features would be a very nice thing to have.
How much would it cost to do this?
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