After several hours of work , my mech extracted the fans.
I managed to replace the Darlingtons yesterday night. They where both open in one junction. Could not test the other components as I did not managed to remove the heat sink . Tomorrow the mech will put the fans again on board. I hope the repair succeeded and I will have again the mid and low speed as in the garage had already put 4 hours of work on the bill…
You might want to replace the ‘crappy-BLUE-Hella relays’ if they are fitted.
86-178A Inoperative Blue Relay.pdf (79.8 KB)
I think there are TWO relays in the fan assys.
One for the fan power and one to ‘short’ across the Darlington Emitter/Collector on HIGH.
If they are Blue Hella, you might at least take them apart and check the contacts?
Andreal …
With the symptoms you described and the success rate of replacing the Darlington transistors I’d be shocked if your repair doesn’t work … shocked I say !
Over the years I had the same problem with both my fans and simply replacing the Darlington repaired them. Actually I had ALL the other electronic bits on hand but decided in the end to only replace the Darlingtons (sometimes it’s better to leave well enough alone). That was many years ago and the fans are still going strong.
1 Like
AFAIK the relays inside the blower housings are Hella brand but aren’t the same relays as on the firewall, they are a type with the internal diode. When I replaced mine, (possibly unnecessarily) I used a standard aftermarket (sealed) diode and soldered an external diode to the pins.
1 Like
The first blower have been remounted and it work at medium and low speed… i hope the other will work too !
the next phase is trying to make the AC working again. Now the situation is that the car have still R12 valves but there isn’t’ enought gas to even start the compressor.
How can i test if the compressor is still working before even attempting to convert the system to another gas?
Place a ‘jumper-wire’ in place of the relay 30/87 (or 3/5) terminals and the compressor clutch should become energized.
3 Likes
Finally i reassembled the XJ-40 dashboard !! the fans are working again at low and medium speed 
now i have to try to have AIRCON again. My mech is sceptical about removing what remains of the R12 (i think is completely empy) and refilling with R134A . What do you think about this? should i try ? here in Italy the Summer is hot and the black leather seats will transform the XJ in an oven without aircon.
Info for you.
82-39am R-134a Retrofits Kits.pdf (25.9 KB)
82-43 PAG Oil for R134a Systems.pdf (48.2 KB)
82-45 Climate Control System – Revised Pipe.pdf (24.1 KB)
82-50 ReceiverDrier AC System Servicing.pdf (29.6 KB)
82-51 Compressor Refrigerant Leaks.pdf (51.3 KB)
I wouldn’t bother with converting to R134A these days as it has been deprecated and will soon no longer be available. No new cars use that refrigerant.
Personally my choice would be R152A (computer duster) but I have a factory R134A system - I run R152A in several of my other R134A vehicles…I believe R152A is also usable in an R12 systems (check yourself) but most R12 systems today use a hydrocarbon substitute refrigerant such as the propane based “R12A” “Duracool” or other proprietary branded substitutes.