Air vent fan not working

[whynot]

No air comming out of the vents when fan is turned on. Checked the fuses and they are ok. Lights on controls are on but no air movment. Any suggestions on what else to look at?

[old Jack]

So I am presuming there is no fan noise so the fan motor is not working rather than air ducts are blocked?

OJ.

[whynot]

Correct, no fan noise.

[Kingbrown]

Apart from the vent fan fuse, there's a relay and a power transistor that complete the fan motor circuit. Relay would be easy to check, firstly by listening for it clicking when fan switch is turned to on (fuse compartment near driver's right knee).
Challenger Airconditioner Schematic HBM12X04AC00ENG.pdf

[old Jack]

There are 7 fuses in the AC system that need to be checked first.

In the Junction box below the steering wheel, fuse #7, #16 #23, and #12.

In the engine bay fuse box, fuses #4 & #5.

Is AC system front manual, front auto controlled or front and rear auto?

OJ.

[whynot]

There are 7 fuses in the AC system that need to be checked first.

In the Junction box below the steering wheel, fuse #7, #16 #23, and #12.

In the engine bay fuse box, fuses #4 & #5.

Is AC system front manual, front auto controlled or front and rear auto?

OJ.

Hi OJ,
The six fuse numbers you gave all checked ok. Wich is the seventh fuse number?
Have tried all dial settings.

[whynot]

Apart from the vent fan fuse, there's a relay and a power transistor that complete the fan motor circuit. Relay would be easy to check, firstly by listening for it clicking when fan switch is turned to on (fuse compartment near driver's right knee).
[ATTACH]34491[/ATTACH]

Hi Kingbrown,

I'm not great at the electrickery stuff but I hear no relay in the fuse compartment when turning on the air vents.

Rear demister activates the bottom left relay, could hear/feel that relay working.
Which relay position is the air fan, can I swap them around to see if that works?
TIA

Cheers
Tim

[Kingbrown]

The defogger relay is on a 30A circuit (same ad the vent fan) so you should be ok to give it a try.

See attached for relay locations.

Challenger Relays Internal Locations AC807315AC00ENG.pdf

[old Jack]

Only 6 fuses in system not 7 my mistake, sorry.

KB has given you relay location, these are micro-relays and it is difficult to hear/feel them operate. If you are going to swap relays agree with KB use the Rear window fogger relay as it is likely to have higher current rating contacts. I am not sure if all relays are the same current rating. If this does not work the the fault finding will get more involved and include dash disassembly.

Is the car still under warranty?

OJ.

[whynot]

Swapped relays and still no go. Front blower relay worked in rear window defogger location so not the reay....bugger.

Vehicle is out of warranty.
Any suggestions on the next step?

Cheers
Tim

[Kingbrown]

The defogger relay and the vent fan relay both share the same supply for their coils. This is from fuse #16.
Since you've confirmed that the defogger relay operates ok, this now points to the coil circuit for the vent fan relay missing its earth connection. (the vent fan relay should operate whenever the ignition key is turned to the IG2 position = engine run).

I would check for earth continuity at the relay coil's 'earthy' side.
Remove the vent fan relay and test the relay earth pin position in the relay socket.

If you aren't confident in identifying the correct pins or in using a multimeter then testing should be left to someone who does know.

Another simple check that could be done is to put a temporarily bridge in place of the relay contacts (NOT the coil !) and see if the fan fires up when the ignition is on.

[whynot]

Thanks Kingbrown, I will get it checked tomorrow by one much wiser than me.

[900canoes]

I gather there is a motor speed resistor in the air plenum situated next to the inboard side of the glove box. I've had this resistor fail in other vehicles but usually only on one speed.
Is the connector still attached? If so it may be worth checking the resistances by removing the glovebox for access.

[Kingbrown]

Schematic shows that speed control is via a power transistor that's controlled by the a/c ecu.
Power transistor location appears to be somewhere to the left & above the driver's left knee.

[old Jack]

Mitsubishi normally place the resistor block in the air chamber of the blower as it provides airflow for cooling the resistors. Common was for the the resistor for the lowest speed to fail on 1980's Mitsubishi's.

OJ.