2 Speed Fan Poser will my woes end!

[Union Wheels]

Hi followers of this thread,

looking at the centre picture in post 118 it seems that the middle relay, which normally runs the second speed in a three speed set up, is being used for the higher speed on the two speed system.

Is it possible that left hand relay is being switched by the engine temperature sensor/ECU, and this has no wires connected to it hence no second speed.

This would account for the 2 clicks, one from each relay, when " French Mikes" test is applied.

I mention this, as information on components being omitted on the control PCB in certain instances has been stated in previous posts. This would seem to suggest that the PCB went through a process of evolution when three speeders were discontinued.
"Jules" also says that some boards seem to work and others don't.

Am I just clutching at straws? Pete.

[RayH]

Originally Posted by Union Wheels

Hi followers of this thread,

looking at the centre picture in post 118 it seems that the middle relay, which normally runs the second speed in a three speed set up, is being used for the higher speed on the two speed system.

Is it possible that left hand relay is being switched by the engine temperature sensor/ECU, and this has no wires connected to it hence no second speed.

This would account for the 2 clicks, one from each relay, when " French Mikes" test is applied.

I mention this, as information on components being omitted on the control PCB in certain instances has been stated in previous posts. This would seem to suggest that the PCB went through a process of evolution when three speeders were discontinued.
"Jules" also says that some boards seem to work and others don't.

Am I just clutching at straws? Pete.

I think you may be clutching at straws Pete
If that were the case then Tony would have no high speed under any condition but he does have it with the trinary test.

[Union Wheels]

Hi RayH, I think you are right.

It needs a scope connecting to the input tag on the control panel and the pulse width monitoring, if pulse is present then voltage checks at potential divider and follow circuit with checks until the fault is discovered.

If pulse is low or missing then check wiring at connectors for corrosion or damaged wires (sometimes insulation breaks down and verdigris eats into wires turning then into resistors).

Can't think of anything else.

Pete.

[rovertone]

I think Phil was also thinking along similar lines to Pete and he did carry out various tests across relays etc. If he picks up on the thread he may expand.

[RayH]

Originally Posted by Union Wheels

Hi RayH, I think you are right.

It needs a scope connecting to the input tag on the control panel and the pulse width monitoring, if pulse is present then voltage checks at potential divider and follow circuit with checks until the fault is discovered.

If pulse is low or missing then check wiring at connectors for corrosion or damaged wires (sometimes insulation breaks down and verdigris eats into wires turning then into resistors).

Can't of anything else.

Pete.

That was my earlier thinking, which is why I asked Tony to check the resistance between the ECU and fan control, but from what Phil has said that appears to be irrelevant anyway as T4 switches it on.

[Jules]

In due course I will duplicate the tests I did in the link mentioned in post 179 using a variable resistor.

But as far I remember my tests "simulating" the various coolant temp fan cut in speeds did in fact trigger all the different fan speeds.

I would have thought many hot country owners would have complained about overheating before now if diesels didn't use high speed for extra engine cooling !!

[rovertone]

Jules,
I will listen out for when you have carried out your tests, if you find the solution I'll no doubt be taking a trip to North Wales. I am due to head off to Portugal again in a couple of weeks and haven't made my mind up yet whether to take the van, either way I hope to put a temporary switch in.
Good point re owners in hot climes.
Tony

[Union Wheels]

Hi rovertone,
you said previously that you had a good rover parts specialist near you with lots of parts. Why not get a working 3 speed fan from him (after all that was the original configuration) and see if that works. He may let you have it on the basis that if it does not work you can take it back.

If it does work and you are then concerned about the longevity of the motor, do my modification (link in my signature) you already have the resistor and bracket on your 2 speed set up.

Cheers, Pete.

[Phil-T4]

The strange thing with that is I tried a 4 wire 3 speed control box and rewired the car back to how the original configuration was. Even then only 2 relays in the control box were energised via the pwm.
At idle we had 3.34v, low speed was at 2.75, medium was 1.75(?) and high was 0.40v.

[FrenchMike]

Originally Posted by Phil-T4

The strange thing with that is I tried a 4 wire 3 speed control box and rewired the car back to how the original configuration was. Even then only 2 relays in the control box were energised via the pwm.
At idle we had 3.34v, low speed was at 2.75, medium was 1.75(?) and high was 0.40v.

Hi Phil,the most significant voltage is across C9.

See what i got on the 3 speed PCB i have tested.(just when the relay energise)

Low=1.6 volt
Med=5 volts
High=8 volts

3 speed.jpg

Mike