Fan speed operation??

[eddiemc05]

Hi all, is there an easy way of testing the fans correct operation, i just want to be sure that all well on that end! When car is running with ac on the fan runs quite noisy, when ac is off the fan goes off , when engine heats up to about 105 the fan comes on but louder, so i assume thats speed 2 and the latter is speed 1, is speed 1 supposed to engage at all without ac on& is speed 2 suposed to engage when ac is on? I am thinking of upgading the resistor soon but would like to know ruffly how it should oprate first, thanks again

[eddiemc05]

Also it seems to be a 3 speed fan as there is no sign of the silver resistor, i have not yet heard 3 speeds/sounds of the 3,

[T-Cut]

The default test for slow speed fan operation is to start the cold engine and press the Demist button. This should invoke the slowest fan speed as required for the aircon system.

It helps to know which engine we're talking about. I assume it's a 1.8 or maybe a V6 from your hot engine/fan test.

TC

[SD1too]

Hello Eddie,

According to MG Rover's official workshop manual 1.8 litre cars were factory fitted with the 2 speed fan system. On this basis, to answer your questions:

Your air conditioning should trigger the fan to run at slow speed (speed 1). In certain circumstances (which have not yet been fully identified) it will not run. If you press the 'demist' button it should definitely run at slow speed. If the refrigerant pressure rises above a certain level the fan will run at fast speed (speed 2).

When the coolant reaches 104 degrees C the slow speed is triggered, whether the air conditioning is on or not. At 112 degrees C the speed increases to fast. The fan switches off when the temperature has reduced to 98 degrees C.

Hope this is reassuring.

Simon.

[eddiemc05]

Correct t-cut its a n/a 1.8, 03, i have read posts by jules and yourself on the fans and types, going by them im still not sure if its a 2 or 3 ive not yet heard 3 speed pithes from fan, i assume its a 3 as i cant see the resister through the grill, but having said that ive read contradictorys as it may be hidden behind the bumper, i breifly scanned an operaion guide posted by either urself or jules but cant find it again?? Also ive seen some posts breifly explain how to test other speeds of the fan i.e by crossing ac pressure or binary switch, is there a complete guide on here on how to test all speeds and even temp sensors, ac pressure sensor, etc

[eddiemc05]

Yes simon very, uve answer some qs as i was thanking tcut, havent had it to 112 yet i think, but only had a quick fiddle with the obd, its looking like a 2 speed then, if so then i know its running at both, is the only service/ pevent, on then 2 speed, a brush change? Id like to prolong reliablity, as us all and so far this is the best forum for any specific car, so good job, ive got a hour or2 tomo to have abetter look,

[chrissyboy]

if the fan is really noisy that would suggest the resistor has gone and it would sound like a hover craft . mine was like that till i boght a upgraded resistor from jules .does the fan run on after you have parked and left the car ?

[SD1too]

Originally Posted by eddiemc05

... is the only service/ pevent, on then 2 speed, a brush change?

You don't need to worry about the brushes on the 2 speed system, only the rectangular resistor. When it fails you'll lose your slow speed. You can buy an upgraded resistor from club member Jules and fit it at any time, but it does require removal of the front bumper.
Edit: Thank you Chrissyboy and Jules for enlightening me on this. Apparently it is possible to access the resistor by removing only the grille (pre-facelift).

Simon.

[eddiemc05]

I fell asleep in a haze of confusion, thanks for all ur help everyone, il get a look today and see what the crack is,

[Jules]

Hi Eddie
Just to contradict Simon (for once ) if there's enough slack on the cables, you can change the resistor just by removing the Grill on a MK1

(if you have a resistor fitted already)