RRRRRRRRRRRRRRRRRRRRRRRRRRRRRR ...................!!! A very bad noise came from the airco / heater and stayed ... We had to take off all dashboard, heater and examine the problem... One (or even both) bearings of the OEM fanblowermotor was completely worn..... Replaced it with a SPAL type 011 A40-22 12 volt motor, using the original fans. Hell of a job but there was no way out ! In the same time, we replaced the transistor 2N5886 which is used for airspeed and which was also faulty .... (only full or no wind). Also then noticed some drops of cooling liquid which was (?) leaking and may have caused trouble in the connectors .... Just some pics to explain...... Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Yeah, indeed, as said "quite some work" aka "a hell of a job" ... And of couse .... unexpected ... and costly ....; hope this will never happen to you all .... But I wonder, was there never one car having the same trouble ... ???
Please look at picture # 4; you can see were it was located: inside the cooling duct. This has to be because the transistor gets very hot and needs cooling. If the transistor is defective, you will find only a full or not working airco fan. A very common fault; many older F types have the same system and also the same problem. Not easy to cure but you could also make the transistor outside the airco unit by tapping the wires... (not a good option IMO) But then you need to cool the transistor somewhere else in a place that gives fresh air (f.i. near the air horns ?) Do you have this problem ?
Yes. It comes on full. This seems to be a very common problem, and I think replacing the transistor with the same will only cause the same problem down the track. Maybe we need to get something abit more robust. I will see what I can find.
Anthony from recollection, there are many threads that have covered this topic before. I think solutions have been suggested including a bigger heat sink and heat conducting paste, e.g. Its worth having a look around first IMO. P
Ok, will do some searches. I mean that transistor is a 25A 80V NPN, and yet it still cant cope. Will check as you suggested. I started looking for a 50A NPN
Done some searches here. I cant believe that a 2n3055 is being used, whilst the higher spec'ed original still blows up. I will be searching for something more robust, and definitely with something at least twice the current rating of the original. Although I cant phathom why the blower motor would suck more than 25A, or 50A peak, which is what the original transistor is rated at. Cooling def has something to do with it: the max heat the transistor wants to dissipate is when the blower motor is at its slowest. less air flow......
Just looking through this thread. In photo 1, do you think there is any way of tracing those wires back and sending 12v just to check if the blower motor is working? Im getting no fan at all except I do get a relay click when setting at full speed, implying it might be the motor. I don't want to go to this trouble to find its not!
As you see on photo#3, the wires get out of the AC bos at one place. try to follow them or find two wires going to switches in (for instance) the middle console ... KEEP us informed too please and place your photos her for all followers. They may get the same problem one day ...
Just managed to get back on this after an issue with my fuse board (replacement due very soon!) Ive managed to find the two wires directly out of the blower motor. I have 12v supply to it, but no signs of life with the fan, so Im guessing its at fault. I'm getting a relay activate under the dash at full speed but no activity! However, before I start stripping out the dash, is it worth looking at the transistor first? I note yours was in the unit but I believe the TR is within the dash?
Not really as the power transistor has nothing to do with full speed operation when the relay clicks. If you're applying +12V directly to the two terminals of the blower motor and it doesn't run full speed = it definitely needs repair/help.
Thanks Steve - I just wanted to make sure I'd covered every base before I dive in! I'll update results when I get around to it.