Member Since: 24 Nov 2017
Location: Pontypool
Posts: 193
Yet another Heater Blower Fault - Now Fixed
Have read through loads of posts relating to the heater blower fault on the D3 and still struggling to fix mine
I have done all of the usual tests and it is not the relay, fuse or the blower speed controller
So far I have confirmed that in the fuse box under the bonnet
12V to relay pin 1 - this is the live feed to energise the relay coil
12V to relay pin 3 - this is the high current feed to the relay that powers the heater fan.
I have continuity from pin 5 to the motor and on to the heater speed controller
If I bridge terminals 3 to 5 in the relay socket then the motor spins up and I have full speed control from the dial on the ATC unit on the dash
If I put a meter from relay socket pin 2 to earth I get a reading of 5V. This is where I believe my problem lies, the relay is earthed switched through the ATC so I wouldn't have expected to see 5v between this and earth
Pin 2 goes to connector C1629-7 on the ATC unit
Diagram with the voltages seen at the various pins
I am going to pick up some male terminals with a suitable current rating tomorrow and bypass the relay so effectively the fan is always on as this is going to be better than freezing my nuts off, will still have automatic speed control just won't be able to turn it off while I investigate further.
I think the next step will be to pull the plug off the ATC unit and check the relay socket again to see if there is still 5V there which might help narrow down where the problem lies.
I am a little concerned about the fues box under the bonnet, there is signs of muddy water having got in there and no I don't water wade with the car but that doesn't mean a previous owner hasn't
Has anyone come across this before or have any sugestions where to go on this?
Last edited by indy4x on 17th Mar 2019 4:31 pm. Edited 1 time in total
11th Mar 2019 10:00 pm
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10359
I have heard about this once before on here.
The fix was to run a new wire in from the cab to the relay.
If you bridge the relay I think it runs slow and flattens the battery.
I recall my temp fix was to use a wire from the heated mirror relay to drive the fan relay coil Iirc.
11th Mar 2019 10:32 pm
indy4x
Member Since: 24 Nov 2017
Location: Pontypool
Posts: 193
Thanks for the info, good point re the heater motor working as it has a permanent live, could possibly switch the LGW wire to earth so I could shut off the fan when not required as a work around
12th Mar 2019 10:07 pm
indy4x
Member Since: 24 Nov 2017
Location: Pontypool
Posts: 193
So I have the ATC unit out of the dash and removed the plugs from the rear of it.
Checked voltages at the relay socket and the 5v I was seeing on pin 2 is now 0V. This is a bit of a as I was hoping to see 5V still which would discount the ATC unit and point to a fault on that wire but this does not appear to be the case.
I want to remove this wire from the ATC plug, from the diagram it suggests it is pin 7 on connector C1629 and looking on the car this does match up as I have a Light Green/White wire to pin 7 on the ATC plug.
Does anyone have any suggestions as to how to remove this wire? I could cut it but would rather do it properly
12th Mar 2019 10:15 pm
indy4x
Member Since: 24 Nov 2017
Location: Pontypool
Posts: 193
I gave up trying ot open the plug so cut the wire instead, no not the blue one
So Light Green/White wire has been cut, soldered in some extra cable and then ran this to earth through a switch. This means I now have a work around so can have a working heater motor and switch off the power to it when the engine is not running.
It does point to an issue with the Heater Control Panel but can it really be that simple?
Looking on eBay they aren't too expensice S/H so will order one and see if this solves the problem
13th Mar 2019 12:02 am
Mossy
Member Since: 01 Jul 2005
Location: Hollyoaks, UK
Posts: 2682
Member Since: 24 Nov 2017
Location: Pontypool
Posts: 193
Hi
Thanks for the link and yes it is one of the threads I have looked at, more the once
I have a working heater, have cut into the green/white wire and ran this to earth via a switch so I now know all of the wiring, relay, fuse and speed controller is working. The switch is there to shut off the fan when the car is parked up as the heater blower will carry on with the ignition off.
For some reason I have 5v coming out of the heater control unit where I believe it should be 0V as its a switch to earth, replacement on route, should be here tomorrow and hopefully problem solved
13th Mar 2019 8:12 pm
indy4x
Member Since: 24 Nov 2017
Location: Pontypool
Posts: 193
This is now fixed
Replacement heater control panel arrived yesterday, fitted it today, tested with a multimeter and don't have 5V from the switch wire for the fan and it switches to earth as required
Now have a fully operational heater
Last edited by indy4x on 17th Mar 2019 11:46 pm. Edited 1 time in total
17th Mar 2019 3:03 pm
Mossy
Member Since: 01 Jul 2005
Location: Hollyoaks, UK
Posts: 2682
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum
as I was hoping to see 5V still which would discount the ATC unit and point to a fault on that wire but this does not appear to be the case.
