Heater Blower Transistor

[sideshowbob]

Car is an '88 635Csi Highline. A/C has not worked in the 13 years that I have owned the car, but this weekend a friend who owns a refridgeration business checked my system out.
To our surprise there was still a small amount of gas in the system and so we regassed the system with the correct gas and lo and behold the system worked.

After this little victory I decided to clean out the heater blower system which involved removing the fan etc. Cleaned out various leaves and other bits and oiled the motor shaft bearings. Reinstalled everything and disappointingly now find the heater blower only works on full setting.

If I switch to the aircon the system blows cool air and the variable speed rotary switch works as it should.

Research leads me to believe that there is a fault with the little circuit board situated in the air duct behind the heater blower, and is probably a failed transistor.

I have now removed mine and intend to replace the transistor.

Previous posts suggest using a transistor 2N3055. But on removing my unit the transistor is a 2N3771.

Both are available but my question is which one should I fit, and if a 2N3055 why is this suggested over the standard 2N3771

Thanks in advance

[Jlc]

I am not an EE, but IIRC the 2N3771 has a higher heat dissipation capacity so in theory be more durable. Maybe someone did a swap way back when? If the 2N3771 worked before I'd stick with that. If it worked before you cleaned it and now doesn't I'd check connections first.

[635sharknose]

I used this one, works perfectly. Don't forget the cooling paste.

https://www.ebay.com/itm/271200130979

MJ11028 BIPOLAR POWER DARLINGTON TRANSISTOR

[TimU]

The original transistors are 2N3055 (10A).
Suitable replacements are:
2N3773 (15A)
2N3771G (30A)

viewtopic.php?p=233826&hilit=2N3055+transistor#p233826

[sideshowbob]

Have now unsoldered all the components in anticipation of replacing the transistor. To be fair the little resistor took a bit of a bashing heat wise to get it released from other components. As I am not as electrical expert can the heat from a soldering iron affect the resistors performance and secondly if so and I have to replace does anyone on here know what the rating is of this resistor. Thanks

[anchored]

I replaced mine a couple times before I ended up with the beefier version. 2N5302

https://www.ebay.com/itm/BSC-2N5302-TO- ... 1654649185

[sideshowbob]

Success....just finished fitting and soldering new transistor in place and it worked perfectly.

Have now after 13 years of ownership got both the heater blower and after re-gassing, got the A/C to work perfectly.

Now off to Lemans Classic............