Heater fan circuit diagram
Discussion
Does anyone have a circuit diagram for the heater fan circuit in an MY04 111S (without air-con)?
My fan has stopped working completely. With the knob on "0", the voltage across the fuse is 0, with the knob on "1", "2" or "3", the voltage across the fuse is 12. Is that consistent with a resistor pack failure or is it something more weird?
My fan has stopped working completely. With the knob on "0", the voltage across the fuse is 0, with the knob on "1", "2" or "3", the voltage across the fuse is 12. Is that consistent with a resistor pack failure or is it something more weird?
rfoster said:
Maybe I'm getting my wires crossed but surely those readings are correct? When the knob is on 0 the circuit is cut, hence no meaure, and when it's on 1/2/3 the circuit is complete and current continues.
No current - I'm measuring potential difference across the fuse bay with the fuse NOT in the slot. I agree that they seem correct which doesn't explain why the fan isn't working 
Edited by kambites on Tuesday 2nd October 13:42
If you remove the front panels so that you can see the top of the heater box, you will find a big black 4 pin connector on the drivers side. this is the main plug to the blower resistor pack. One wire is the earth and the other 3 are for speeds 1, 2 and 3.
If you use your volt meter and stick the neg lead into the black wire and the other lead into any of the other 3 wires, They should each have 12v in turn when the knob is turned, If all 3 wires have 12v when the knob is turned then it's going to be the resistor pack at fault,
Its a clam shell off job to get the blower motor out. The resistor sits at the bottom of the blower, normally in a pool of water (poor design) and so causes the connectors to corrode.
Hope this helps.
If you use your volt meter and stick the neg lead into the black wire and the other lead into any of the other 3 wires, They should each have 12v in turn when the knob is turned, If all 3 wires have 12v when the knob is turned then it's going to be the resistor pack at fault,
Its a clam shell off job to get the blower motor out. The resistor sits at the bottom of the blower, normally in a pool of water (poor design) and so causes the connectors to corrode.
Hope this helps.
wezzer-45's said:
If you remove the front panels so that you can see the top of the heater box, you will find a big black 4 pin connector on the drivers side. this is the main plug to the blower resistor pack. One wire is the earth and the other 3 are for speeds 1, 2 and 3.
If you use your volt meter and stick the neg lead into the black wire and the other lead into any of the other 3 wires, They should each have 12v in turn when the knob is turned, If all 3 wires have 12v when the knob is turned then it's going to be the resistor pack at fault,
Its a clam shell off job to get the blower motor out. The resistor sits at the bottom of the blower, normally in a pool of water (poor design) and so causes the connectors to corrode.
Hope this helps.
OK thanks. I'll have a look at that tonight If you use your volt meter and stick the neg lead into the black wire and the other lead into any of the other 3 wires, They should each have 12v in turn when the knob is turned, If all 3 wires have 12v when the knob is turned then it's going to be the resistor pack at fault,
Its a clam shell off job to get the blower motor out. The resistor sits at the bottom of the blower, normally in a pool of water (poor design) and so causes the connectors to corrode.
Hope this helps.
I have no problem with taking the clam off to replace the resistor pack. I just don't want to go out and order a new pack and then find that that wasn't the problem after all.
If it is the resistor pack, what should I do to avoid the problem happening again? The two options I've heard banded around are to smother the new resistor pack in grease to avoid letting the water in, or to drill holes under the resistor pack to let water drain. Should I do either or both of these or have lotus waterproofed the later resistor packs anyway?
The bulletin says to drill 4 6mm drain holes from underneath the car into the planked looking section directly under the heater box. approx 20mm in from each of the corners. make sure tha you don't drill in too far and drill the heater box. I've also covered the resister pack with vasoline to stop the connectors corroding.
happy clam shell removal.
happy clam shell removal.
wezzer-45's said:
The bulletin says to drill 4 6mm drain holes from underneath the car into the planked looking section directly under the heater box. approx 20mm in from each of the corners. make sure tha you don't drill in too far and drill the heater box. I've also covered the resister pack with vasoline to stop the connectors corroding.
happy clam shell removal.
Cool. Thanks happy clam shell removal.
Any advice and/or instructions for getting the clam off? Sounds like you've done it before.
Yeh, I've done a fair few, I'm a Lotus technician in a dealership in Cardiff.
You need to be very gentle when removing the clam as it will crack very easily, the worst place to crack is the narrow section in the centre.
Removal as follows,
Jack up front, remove wheels and arch liners
remove headlamp lenses, 3 fixings on each, remove/disconnect headlamp wiring
remove allen bolt from headlamp apperture
remove 10mm bolt and shims from clam to sill joint
Open doors, slacken 10mm bolt and remove shims from sill to clam joint (leave bolt in, sill is slotted)
remove allen bolt and shims from top rear corner of clam (from door shut)
Remove top clam panels and grills, remove alen bolt
remove 2 10mm nuts from underneath rear centre between the removed panels (a bit difficult)
remove front undertray
remove driving lamps if fitted
remove 10mm bolt from inside front of wheel arch, inside front box section (where oil cooler should be)
The clam should now be loose and will need to be carefully lifted in the centre off the 2 studs and also pulled upwards to clear the radiator housing. They can be a bit tight, just be carefull not to crack it.
It normally takes 3 of us to lift off the clam. One each side and one in the front centre to lift it over the rad housing.
The heater box is also fiddly to get out. once all of the hoses and wires are disconnected the blower must be split from the heater box and the heater box must be removed first. the blower can now be pulled out to reviel the corroded resisror pack and normally burned wiring.
I think lotus mormally allow approx 4.5 hours for the whole job start to finish.
have fun and don't get too stressd out. It's not as bad as it looks.
You need to be very gentle when removing the clam as it will crack very easily, the worst place to crack is the narrow section in the centre.
Removal as follows,
Jack up front, remove wheels and arch liners
remove headlamp lenses, 3 fixings on each, remove/disconnect headlamp wiring
remove allen bolt from headlamp apperture
remove 10mm bolt and shims from clam to sill joint
Open doors, slacken 10mm bolt and remove shims from sill to clam joint (leave bolt in, sill is slotted)
remove allen bolt and shims from top rear corner of clam (from door shut)
Remove top clam panels and grills, remove alen bolt
remove 2 10mm nuts from underneath rear centre between the removed panels (a bit difficult)
remove front undertray
remove driving lamps if fitted
remove 10mm bolt from inside front of wheel arch, inside front box section (where oil cooler should be)
The clam should now be loose and will need to be carefully lifted in the centre off the 2 studs and also pulled upwards to clear the radiator housing. They can be a bit tight, just be carefull not to crack it.
It normally takes 3 of us to lift off the clam. One each side and one in the front centre to lift it over the rad housing.
The heater box is also fiddly to get out. once all of the hoses and wires are disconnected the blower must be split from the heater box and the heater box must be removed first. the blower can now be pulled out to reviel the corroded resisror pack and normally burned wiring.
I think lotus mormally allow approx 4.5 hours for the whole job start to finish.
have fun and don't get too stressd out. It's not as bad as it looks.
wezzer-45's said:
If you remove the front panels so that you can see the top of the heater box, you will find a big black 4 pin connector on the drivers side. this is the main plug to the blower resistor pack. One wire is the earth and the other 3 are for speeds 1, 2 and 3.
If you use your volt meter and stick the neg lead into the black wire and the other lead into any of the other 3 wires, They should each have 12v in turn when the knob is turned, If all 3 wires have 12v when the knob is turned then it's going to be the resistor pack at fault,
Its a clam shell off job to get the blower motor out. The resistor sits at the bottom of the blower, normally in a pool of water (poor design) and so causes the connectors to corrode.
Hope this helps.
Well I found the plug you're talking about (actually my car has two 2-pin connectors).If you use your volt meter and stick the neg lead into the black wire and the other lead into any of the other 3 wires, They should each have 12v in turn when the knob is turned, If all 3 wires have 12v when the knob is turned then it's going to be the resistor pack at fault,
Its a clam shell off job to get the blower motor out. The resistor sits at the bottom of the blower, normally in a pool of water (poor design) and so causes the connectors to corrode.
Hope this helps.
Then, after a bit of hunting around, I found the socket it was meant to be plugged into - it had fallen out.
The connector turned out to be a read herring. I think I must have bashed it loose when removing the plastic bits under the access panel and then plugging it back in remade the dodgy connection on the resistor pack... anyway the fan failed again a few days later. Still trying to find time to take the clam off to look at it.
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