A/C Fan won't turn off...ever

LXL15 · 12-01-2011, 01:47 PM

Hey guys,

Today my internal A/C fan (the one behind the glovebox) just wouldn't turn off. I tried turning it off using the climate control (it's a Fairmont), turning the car off and removing the key. Nothing. It just kept spinning, blowing out warm air. The only way I managed to turn it off was by removing the A/C fuse from the engine fuse box. It just turns back on if I replace the fuse. It seems to be stuck on a minimum speed, as I can turn the car on and turn the fan up on the climate control, but it won't go below a speed of around 3 or 4.

Can anyone help?! It also makes a noise as if the blades are rubbing on something, so if I have to remove the unit to fix it, I guess that's okay, as long as someone tells me how to do it, if it's possible to do yourself.

Cheers,
Alex

T3man · 12-01-2011, 04:15 PM

It is most likely a fault in the CC unit in the dash - if there is a reset procedure you could try that (doesn't work on AUs or at least not for me!) or else substitute another known good working unit to see what happens. There is also a way of getting fault codes out of the CC unit I believe so refer to your handbook or try your local friendly Ford dealer.

LXL15 · 12-01-2011, 04:31 PM

Thanks T3man. Where should I try looking for the reset procedure? Or what was the reset procedure you tried?

Dezza · 12-01-2011, 05:34 PM

I had this issue on my EA, and it turned out it was the fan speed controller behind the glovebox. Unfortunately I'm unsure how similar the system is in AU, whether it's still at the same spot.

T3man · 12-01-2011, 07:30 PM

Here's some excerpts from the workshop manual that may help you.

FAULT WARNING MODE - if the temp display flashes for approx 6 secs when IGN is first switched ON, a system fault is indicated.

So if that happens (or even if it doesn't and you want to check anyway) you can then enter the SELF TEST MODE -

Warm engine coolant to at least 45 degrees C
Turn IGN switch ON
Press MODE and OFF buttons simultaneously and release
The control does a self test (shows all segments of the display for a few secs) - when the self test is completed and if the system checks out OK the display will read OFF. If the system has a fault the display will read E and a number from 1 to 8. In case there is more than one fault code you can cycle through all codes by using the AUTO button.

Now if you can get it to work for you and any E Codes show up let me know what they are and I can refer to the list for you. However there is no code for a faulty blower - go figure. The whole exercise may just be a waste of time for you but for future reference it's probably handy to know.

BTW Pressing the AUTO button is also the way to exit the Self Test Mode so if no codes are thrown just press it to reset the system to normal operation. Furthermore, you then need to do the IGN OFF/ON cycle two more times before starting the engine to ensure the system is reset.

**aussiblue** · 12-01-2011, 10:28 PM

The main transistor in the fan speed controller that sits in the a/c air intake duct to keep cool will have corroded and shorted. Leaves and moisture get caught in the duct sit on the transistor casing and rust it away. Replacement transistor can be had from Worldwide Electronics http://members.iinet.net.au/~worcom/ for less than $15. The symptom of the transistor's failure is a fan that stays on high speed or stays on all the time.

The transistor is Motorola 2N5686 (Ford used to own Motorola). The fan speed controller box (silver metallic held by two screws behind glove box) opens easily by bending the tabs and its not too hard to unsolder the transistor and replace it - just ensure the orientation is correct so you don't reverse wire it (very easy to do as it seems to fit better the wrong way around).

To prevent the transistor failing again I suggest you add a TO-3 plastic cover (Cat ZM-0004 at Jaycar, Cat H7290 at Altronics, Dick Smith have them but I can't find it in the catalogue) and /or an additional TO-3 heatsink (part number H3400 at Disk Smith, Cat number H0610 at Altronics, and HH8510 at Jaycar). These will keep the leaves away. You can also spray the transistor's outer case with circuit board lacquer or something similar for added protection.

See also page 6 & 7 of this thread http://www.fordforums.com.au/showth...05&page=6&pp=25
__________________

LXL15 · 13-01-2011, 07:00 PM

Awesome thanks guys. I might give that reset thing a miss T3man, sounds a bit too easy for me to stuff up haha.

Blue, can you tell me how to remove the fan speed controller? I just tried, but all the wires in front of it stop me from being able to pull it out enough to drop it into the footwell. You're right though, it's chockers with leaves.

**aussiblue** · 13-01-2011, 08:29 PM

Quote:

Blue, can you tell me how to remove the fan speed controller?

Make sure all the retaining screws are out - ones hard to see and unplug the wiring hraness from it. Then it's a matter of some twisting and turning and some gentle persuasion. It's a tight fit and you have to have it twisted at a ceratin angle with some firm pulling force appled.

McPants · 13-07-2011, 04:24 PM

Big thanks to this forum for the wisdom, to give this a go myself,

My scenario was very similar. 1999 Fairmont, Came home last week and turned key off, Fan kept going. Pulled fuse from under bonnet to stop it.

Great advice from Blue to get the fan speed controller out and also getting a new Transistor from World Wide Electronics. Mike posted out a new one right away. TO-3 Cover from Jaycar and ready to go.

Unsoldered the corroded Transistor and in with the new. Cover on top, back in car and works great.

Very thankful for this Forum

LXL15 · 13-07-2011, 07:14 PM

Yeah thanks again Blue, it worked perfectly for me too. And the extremely specific information was all the help I needed, entirely accurate.

**aussiblue** · 13-07-2011, 08:23 PM

Glad it worked out and I was able to help.

Mr Hardware · 13-07-2011, 09:58 PM

awesome writeup mcpants
i'd say that'd be the most helpful first post EVER.

McPants · 16-07-2011, 01:57 PM

Thanks, Im just thrilled to save several hundred dollars and have the satisfaction of fixing it myself. All up took around 2 or 3 hours....Bit of cursing getting it out....$19.50 for transistor and postage and another $1.00 for cover.

I'd recommend anyone else doing this to take photos before taking it apart as i needed them to put things back in correct place / orientation.

Otherwise quite an easy job.

(As the first one lasted 11 years, i'd assume the car will be dead before the next one corrodes)

**aussiblue** · 18-07-2011, 08:21 PM

I just had to replace the one in the NB I replaced about 15 years ago. The resin coating and cover worked - no corrosion and looked as good as new but dead as a dodo; so it seems they have a limited life even without corrosion.

Bad new was that while cleaning the new leaves out of the vent behind the fan speed controller I noticed the heater core appears to have coolant seepage and replacing that I think is a full dash out job.

dnk · 26-07-2011, 06:21 PM

I had the same problem, but couldn't source the transistor. A 2N3055 from Dick Smith or Jaycar works just as well. You might want to replace the transistor's insulator washer and bushes as well.

McPants · 22-01-2012, 08:48 PM

Just a warning, That plastic cover i put on the Transister caused it to overheat and blow again. This time the aircon would either turn off or work at full speed, but nothing in between.

I ordered 2 new Transiters from hong kong for about $7 on ebay.
Second time around it was a quick job to replace and back up and running again. Didnt bother with cover this time. Our summer is too harsh.

**aussiblue** · 22-01-2012, 11:01 PM

Quote:

Just a warning, That plastic cover i put on the Transister caused it to overheat and blow again. This time the aircon would either turn off or work at full speed, but nothing in between

Shouldn't I had on on for more than 10 years in the hot WA climate - more likely a the case or leg was shorted somehow.

rowan194 · 23-01-2012, 02:23 PM

Quote:

Originally Posted by McPants

Just a warning, That plastic cover i put on the Transister caused it to overheat and blow again. This time the aircon would either turn off or work at full speed, but nothing in between.

I don't think the cover would make much difference, the majority of the heat would still transfer via the bottom of the transistor to the metal underneath it (at least it looks like metal)

**aussiblue** · 23-01-2012, 10:20 PM

There are also some counterfeit chips around that aren't up to spec.

McPants · 27-01-2012, 11:30 PM

Yeah maybe just a dudd

ClunkyMunky · 21-05-2012, 04:46 PM

Well.
I have had this thread bookmarked for about 3 months and no air conditioner after the dreaded "fan on high even with no key in the car" symptom.
Pulled the fuse and was happy for a while.
Now that the weather is getting cold - I decided a heater would be nice in the AU Failane (not a typo) and thought I'd give this a try.
After not realising there was a third screw in the back of the unit I managed to get the unit out after a bit of swearing.
Ordered the new transistor from worldwide electronics and exchanged the transistors - paying careful attention to the orientation of the unit and which probes were soldered to which bits on the PCB.
Put it all back together and popped the fuse back in.

Well as you can probably guess by now - nothing changed. Fan still stuck on high.

I'm not really sure where to troubleshoot from here?

nassi · 21-05-2012, 08:21 PM

Quote:

Originally Posted by rowan194

I don't think the cover would make much difference, the majority of the heat would still transfer via the bottom of the transistor to the metal underneath it (at least it looks like metal)

It could be a lack of heat sink compound ( that white stuff under the transisitor when you removed it). The picture shows the transistor mounted to a heatsink so it would need the compound to work efficiently. If all this werte in place, the plastic cover should be fine. JMHO.
cheers

ClunkyMunky · 24-05-2012, 05:59 PM

Auto sparky solved it - fan speed relay or something. Meh - anyway at least my wired up transistor works :P

terence moy · 23-09-2012, 03:37 PM

Hi all, I;m experiencing simmilar problems with my 1992 EBII Tickford Ghia,
I have replaced the transister 2N5686G,Now it runs for a few minutes on cool with air coming out the dash vents and then it changes to the floor and cooks inside for a while then changes back to the dash vents and cools and keeps repeating this. I am at a loss as it seems to have a mind of it's own,
Any suggestions here are most welcom.
Thanks
Ted.

**aussiblue** · 23-09-2012, 06:04 PM

Do the self test as this may reset it. Also check the vacuum hose hasn't come of the end of the inlet manifold near the firewall .

terence moy · 30-09-2012, 07:49 AM

Thanks Blue.
Tried all that with out success, I'm told I should look into the Cabin Sensor Sniffer as this can lead to the fluctuations of the fan as well.
Does anyone have any clues as to how this works or symtoms that could show this to be faulty.

Thanks
Ted.

terence moy · 14-10-2012, 05:42 PM

Hi Guys
After puting a new transistor in the fan control unit I have re attached the sniffer which had broken free.Now for the last 3 weeks it has worked a treat.
I drove it to Newcastle yesterday and back probably 5 hours and found it to work perfectly only to get home to find it went to the floor for a while on full heat then back to the dash outlets. Then I experienced that the fan was hunting up and down with out the fan speed on the screen changing.
When I turned the car off I found the fan still running on a low setting.
So I had to disconnect the fan.
Today I reconnected the fan which was still running with the ignition off.
I drove it for a while then the fan went to high with the fan speed on 1.
I turned the engine off with the fan still running then it went to the screen full bore even with the ignition off. So I have disconnected the fan yet again.

Has any one any idear as to why it would do this and what is the fix.
Surely I'm not the only one to experience problems like this.
Thanks
Ted

**aussiblue** · 15-10-2012, 10:08 PM

Sniffer come adrift again? Short to case from lack of or incorrectly fitted insulating washers on transistor?

I see here http://au.mouser.com/Search/Refine.aspx?Keyword=2n5686 the 2N5686G has a higher temp rating than the old 2N5686 so it should be a slightly better replacement too.

**aussiblue** · 15-10-2012, 10:12 PM

see http://www.fordforums.com.au/showthr...5&page=6&pp=25

terence moy · 11-11-2012, 01:23 PM

Thanks for the info Blue.
I have sent my spare fan controller to Injectronics for rebuild as they are listed in their catalogue under P/N 9140066009C0.
PHone 03 8792 6999 Fax 03 8795 7205
www.injectronics.com.au. Melbourne.
See how it goes when it returns.
Thanks
Ted.