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air conditioning not working

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  • air conditioning not working

    My radiator has a leak and I cant afford to replace it, so to cool the engine I've bin putting the air conditioning on. Problem is it's now stopped working... the fuse had blown so I replaced it but it still wont work can anyone help?
    Last edited by E_T_V; 4th October 2004, 19:58.

  • #2
    heater fan

    This is quite a common-ish fault apparently with maestro's
    and montego's they just pack up.Recently had mine transplanted
    at a cost of 85.You could do it yourself,but it's a dash off job.
    I originally thought my fuse had blown,but after trying 3 new ones
    and trying to find a relay(only to find there isn't one for the heater) i gave up and left it to the experts...


    • #3
      As mentioned, common Maestro/Monty problem. It usually fails in two ways. One, no operation, except only very occasionally,
      And two, operation on only one position on the switch.

      The first is caused by corrosion and a loose connection direct onto the heater fan, the 2nd is failed windings on the rheostat. To fix both, the dash has to come out, and the heater unbolted from the bulkhead. The 1st problem costs nothing to fix, the 2nd depends on your source, as a Metro rheostat can be adapted, and easily obtained from a scrapper, as they sit open in the engine bay.
      Last edited by E_T_V; 4th October 2004, 20:01.


      • #4
        The comman faults with the heater are usually the motor itself, or the "otterstat" thermal overload cut out. When the latter goes, the fan will only work in position III.

        Check the fuse first, if the fan still does not work after replacement, check for voltage at the switch. Only the centre terminal in the multiplug connector (if i remember correclty) should have a voltage on it, all the others are a glorified earth. If the motor has gone it is most likely the carbon brushes have worn out, or the commutator is worn, or both. A lose connection may be the case where the wires join the motor. To access the motor terminals the cover must be prised off the side of the motor where the wires pass through a small grommet. To remove the motor, the entire unit must be stripped down, before the impeller can be removed from the motor, and the motor pulled free. You would be best off removing the entire unit from a scrap car and swopping them over.

        When the heater only works in position III, the fault is caused by corrosion on the thermal overload cut out or "otterstat", this is a small unit, with a bi-metalic strip in, and works like your central heating thermostat would, exept is is preset at a temperature. There are two coils of resistance wire wound into coils and fixed onto a board which sits in the airflow of the fan to keep them cool. If the fan fails, and the coils overheat, the "otterstat" will cut the power before any damage is done. This is a pain when it goes wrong, the "otterstat" corrodes so that the circuit is always open, thefore speeds I and II will no longer work, but III which by passes the setup, and requires no resistance as it works on full 12v will still work.

        Two fixes to this, either, get a new one, but the entire heater unit has to come to bits to replace it, and the whole section of the wiring loom has to be replaced, or simply pull the heater unit forward, and solder over the two terminals on the otterstat. Shown in pic. Not 100% safe if the fan fails and you leave it on I or II as the coils will overheat.

        Metro resistors sit under the heater motor in the engine bay, but these are entirly different and are wond to only create 1 low speed and 1 fast speed, so a 2 speed fan rather than the 3 speed.

        Attached Files


        • #5
          The Maestro/Montego manuals clearly state that you should switch your heater/blower fans off with increased road speed as they work effectively then anyway. I imagine this is because you 'overrun' the fan and with time wear it out if you have it at II/III setting whilst driving along at say 40 mph+. I switch my interior fan off at every opportunity because for one I can't be bothered with getting it repaired if any of the speeds did pack up.:laugh:

          1989 MG Maestro Turbo no.399

          1994 Maestro Clubman Turbo Diesel


          • #6
            Anyone would think this was a common problem..:laugh: (both of mine have gone..although it comes back in the rain..!)