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MG MGF Technical - Heater fan control

Heater fan control only working in 3-4 speeds have replaced switch same problem! can you help
M V Turner

Replace the Heater Speed resistor Pack. Item 2. http://www.lame-delegation.de/mgfcar.de/epc/1230.htm
Geoff F.
Geoff Farthing

Me too - my speed 1 is no good. Other speeds OK.

It's not the switch, I believe it's the resistor wire coil(s) that break over time and need replacing.
See http://www.mgfcar.de/heater/heater.htm for removal etc.

Resistor wire is available from Maplins if you can use a soldering iron.

Good luck

Jeff
J Lennon

Thanks guys! off to the scrappy again!!
M V Turner

Tried Ebay and discovered this seller


http://cgi.ebay.co.uk/ROVER-HEATER-FAN-RESISTOR-REPAIR-KIT-200-400-25-45-MG-F_W0QQitemZ250601911728QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item3a5909b5b0
M V Turner

Hey try this site


www.rezpax.com


Sorted!
M V Turner

I had the glove box out today to get at the resistor pack. The usual howto's fail at this stage - I have air con fitted! There's no way I want to remove the a/c box to fix the resistors and then have to get the system regassed - so what's to be done?

Logically the power feed to these resistors is via each of the 4 positions on the fan switch. I've dismissed the idea of relocating some wire wound or ceramic resistors behind the switch as they need moving air or a heat sink to dissipate the heat of the wasted voltage. Maybe an electronics expert could devise a circuit to deliver variable voltage (or appropriately timed 12v pulses) to the fan motor according to switch position?

During research of the above I've seen references to a guy in Jersey called Bill Nixson aka willyphixitt - it seems he's already been there done that. Does anyone know how to contact him?

Jeff
J Lennon

I have sent him your message!
Charless

Thank you Charless

Jeff
J Lennon

Removed resistor pack and sure enough two resistors burnt out, will be sending to


www.rexpax.com


Postal repair service turn around within a week for around £12.00inc

M V Turner

Should of been



www.rezpax.com


M V Turner

Hi MVT, did you sort your earlier windows problem?
Charless

Hi Jeff,

I've just picked up my e-ails. As Charles has said I can sort your heater fan problem without resorting to tears. I am currently still away from home on holiday in Germany. I will be back for Easter. I will be in touch when I get back.

willyphixitt
Charless

Hi Charless

Windows sorted have serviced the window mechanism, Fuses seem to be holding out


Cheers


M V Turner

Hi Jeff,

I'm back home if you wish to contact me with regards to sorting out your heater fan speeds.

willyphixitt
Charless

How did I do the above - posted as Charless. Sorry Charles.

I repeat, Hi Jeff, I'm back home, so if you wish to contact me with regards to sorting your heater fan speeds, you can e-mail me at willyphixitt@madasafish.com

willyphixitt
W A Nixson

Absolutely no cause to apologise Bill, I am as bamboozled and relaxed as you, both times!
At least there are no moderators on this great original site to ask.
Charless

Thanks Charless

Will make contact with himself direct.
Will post details here, as and when Bill is OK about this.

Jeff
J Lennon

Resistor pack sent rezpax.com and returned fitted and working on all 1-4speeds within 3 days

Thanks for all comments

M V Turner

Mmm so easy without aircon.
Charless

With aircon it'd be a bit of a nightmare - but for those of us without, a relative doddle!

Can anyone confirm the resistor values for each fan speed? There is some confusion on other web resources - and where to purchase the resistors from. But I can't see any reason not to get some ceramic resistors from your local branch of Maplins!

That said, an exchange service for 12 quid is probably worth it for the convenience alone!

Is this replacement with resistor wire (as original) or ceramic solid resistors?
Rob Bell

Am eagerly awaiting delivery of Bill Nixson's electronics solution to the blown resistor(s) in my aircon vehicle. Bill's circuit bypasses the traditional resistors - they become redundant.

At £40 Bill's solution is more expensive than replacing resistors, but arguably has a longer life. It will fit all MGF's with or without aircon.
In aircon vehicles fitting his circuit avoids having to dismantle, reassemble and regas the aircon plant. A regas will cost £50 or so -it is not something you can DIY.

Jeff
J Lennon

How does that work then Jeff? Need pictures! :o) Variable resistor?
Rob Bell

Hi Rob,

My solution is to use the original selector switch to tap into a resistor chain that varies the output pulse of the timer driving a high power switching transistor (.009 ohms "on" resistance). As the switch also supplies ground to the aircon circuit, I have to add another bit of electronics to supply this ground as the switch is not any more in the ground circuit. The unit bolts just forward of the speed selector switch, mounted on the metal plate that's exposed when you remove the cover in the left footwell containing the footwell light.

The non-aircon version obviously does not require this additional circuitry. However it takes almost as much time to build. The existing wiring to the resistor pack is now redundant. The wires (from the switch) that go to the motor and ground now go to the electronics unit, as does the aircon lead where necessary. One additional wire is all that's required and this supplies 12 volts to the electronics. I will post a photo later. I've got to go out shortly to an important meeting.

Jeff, your unit will be started tomorrow. Run out of some bits that RS could not supply. Also been interrupted by a few house problems that needed dealing with.

Regards.

willphixitt
W A Nixson

Bill, just send the unit when you can, there is no need to rush it. I'll do a photo shoot for the group to show the installation when I get my paws on the circuitry.

Regards

Jeff
J Lennon

Very nice solution :o) Gets rid of those antique wire coils too!
Rob Bell

Hi Rob,

A much better option than replacing the resistor coils. Electronic switching is far more efficient. I can remember when a kid playing with my train set. As you rotated the speed controller, nothing happened apart from a hum then suddenly the loco would take off at too fast a speed, and you would have to immediately reduce the speed. When electronic control came in, what a difference. You could easily make the loco creep as slowly as you like and also maintain a consistent speed. This is because the motor is getting full voltage and hence maximum torque.

I can understand folks changing the resistors only as it's a cheap option if you do it all yourself, however, choosing the right value resistors are crucial not to shorten the motor's life as you can inadvertantly cause the motor to draw too much current.

Having a complete fan assembly to use as a test bed, I can see that there's no way of stripping the motor down even just to lube the bearings. The heater fan motor in my F draws around 9 amps max. The one I use for testing draws a whopping 15amps - ouch! I've had to make sure my units can handle such a currents with ease, especially as the units are not in any airflow to cool them down. To this end I use transistors capable of handling 100amps. The diodes to protect the electronics from back emf are 15amp ones.

willyphixitt

W A Nixson

That's quite a beast! Most of my home electronics projects use fraction of an amp: automotive circuits are on an entirely different level aren't they!

Actually, I really need to inspect the resistor coils in my car. Usually I run the motor on speeds 3 and 4 (more often than not I drive roof down, so having a bit of extra warmth is welcome) - but when it comes to replacing them, I'll either DIY it, or come calling on you!

How much does your widget go for Bill?
Rob Bell

Hi Rob,

I do the standard unit for £35-00 and the aircon version for £40-00, which includes "recorded delivery" to the UK. This may change from the 8th May as Jersey Post are introducing size as well as weight when it comes to postage prices. RS also keep putting up their prices - a lot more than than rpi. I may have to do another material costing in the future. Some items I've not added as I've been using old new stock when it comes to fasteners etc. However I'm trying to keep within the cost of buying an oem resistor pack because for the aircon version it's very good value for money, especially when you consider that you do not need access to the oem resistor pack. Attached is photo of a standard version. However it does not come with the moulded plug. This has to come from the owner's car. Getting the plug out and then the old leads out can be a fiddly job, but after that it's very straight forward. I can send you fitting instructions for you to peruse should you so wish. Just need your e-mail address.

Regards.

willyphixitt

W A Nixson

This thread was discussed between 24/03/2010 and 19/04/2010

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