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Heater Control Module for GT3- Supplier ? - Interior/Exterior/Lights/Glass/Alarms/ICE/HVAC - The Lotus Forums #ForTheOwners Jump to content

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I am trying to trace fault on my HVAC (blower diversion to footwell and screen not working + Only Cold Air).

After a bit of research I discovered that a Heater Control Module (located passenger footwell, behind wheelarch on RHD cars) can and does fail and it seems to control blower flaps and temperature. Further that no test procedure other than to replace and trial with 'known operating unit'.

The problem:- Lotus Parts list as not in stock; "a bespoke part which the buyers are unlikley to re-order and will probably to be listed as obsolete" : Lots of help, thanks Lotus !

I don't yet know for sure if this part on my '98 GT3 has failed, but its looking suspiciously likely.

Part number I have is A082 M5075F

Anyone out there know :-

A- Is this a bespoke piece or can it be found on other vehicles ?

B- How best to go about getting a design spec. & original manufacturer from Lotus (I may possibly commission or redbuild)

ian P ('Deep Purple' Esprit GT3)

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Hi Ian,

I would say that chances that this module has gone is slim rather than a vacuum elbow splitting. It's happened to mine a few times. Also the other likely culprit could be the stepper motor. This is located on the right hand side of the heater and controls the flaps. The resistors burn out inside (there are two of them). You could try fixing yourself but I don't recall the resistor values and this is essential to get the stepper motor to work right. Chances of being able to read the stripes is slim as they tend to go black or burnt when they go.

I did have a spare module the one you are looking for but I gave it to PNM. Iam pretty sure they still have it. From memory, it had a broken corner off the unit where you screw it to body of car.

If your stepper motor has gone then the part number is A082P4462F and last time I checked the price was £131.59 + VAT. PNM can also refurb your old unit but you'll have to wait a while. It's about half the new price off top of my head.

A guy called John Rotherham Esprit73 or EspritV8 or V8esprit73 is his user name might also have a spare stepper motor from his race car.

Hope this helps,

David Walters

PS, one way to determine whether your heater module has gone or not is to send it to me and I plug into my V8. Or find a local GT3 or late V8 owner willing to let you plug into their car. It's easy to remove once you can get to it. I've done this for other owners in the past.

the stepper motor is more tricky to remove and test but I would be prepared to do this for you.



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Another vote for the stepper motor, but you are only going to find out by removing the part and looking. Heres my stepper that Jon managed to repair :construction:


Edited by LooseCannon

In the garage no-one can hear you scream 

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Thanks Guys- really useful responses;

My Stepper motor seems to work ok (I think only one of these - located in the drivers footwell ? I ask because i think someone mentioned two in a thread i saw somewhere).

Thinking about the module I rather agree with David that it unlikely to be the unit and more likely a failure /fault on the pneumatics connections etc; I will check those out at the week-end and post results.

Thanks for the offer to swop a known functioning units - I may need to take-up that option.

Watch this space !

ian P ('Deep Purple' Esprit GT3)

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  • 6 months later...

My stepper motor is misbehaving now.....Steve Williams is investigating why my heater controls don't work properly and has found that the motor just cycles round rather than stepping. The shaft that runs through the blue pot on the circuit board was fairly loose, I've tightened this up but don't hold out much hope of that fixing the problem. Anyone know of where I can get a replacement unit or even a replacement blue pot?


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Ok, as far as I can tell the stepper motor itself is absolutely fine: the motor works fine and the pot shows correct resistance across the complete range. In operation, on demist the motor oscilates backwards and forwards, on footwell only it trembles slightly but the middle two positions are fine.

Presumably this could be the HVAC that 64 on the parts list?

How did you get on with yours Ian? and can you give me a hint where in the passenger footwell to find it?


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  • 3 weeks later...


In my case, the problem turned out to be with the vac supply rather than with the control module. As you will find from the various threads on this subject, the most likely source of trouble with the HVAC does appear to be the vac lines which are vulnerable to dislodging and/or cracked rubber seals where the vac line attaches to the various solenoids and to the vac pump.

So fortunately I never had to source a replacement module, but i did try several parts suppliers and got the same story each time : declared 'obsolete' by Lotus.

A couple of experienced Esprit mechanics that I spoke to did report that very occasionally the HVAC can throw up fault which are difficult to trace and that in those cases it is a good idea to replace the control module with 'a known good one' - which is apparently what the lotus servicing manual recommends. This sounds like what you might need to do in order to progress.

The module is in the passenger footwell, behind the carpet at the 'feet' end of the well (nicely positioned so that it is vulnerable to damage from then passenger's feet !).

ian P ('Deep Purple' Esprit GT3)

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