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1970-1995 Range Rover Classic
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91 Posts
Jos Geuze said:
If the blower is running at full speed it indicates a short to earth that bypasses the speed regulation electronics.
the high speed relay does exactly this. it will "short" to ground the leg of the transistor that will allow full current to flow through the transistor. this gives you the highest speed.

rtkraken: the high speed relay is on the circuit board next to the two transistors.
there is a thread around here somewhere that someone posted the pn and method to replace these transistors with parts from an electronics store. a little searching should bring it up.
 

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1970-1995 Range Rover Classic
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91 Posts
ahh here it is.
viewtopic.php?f=3&t=32538&hilit=blower+motor+transistor

i had this same constant high fan setting on mine. i pulled it out and cleaned it up but to no availl. the high speed relay was working when bench tested and had good coil resistance and good contact. so I suspect the transistor(s) were just blown and allowing full current flow all the time. a replacement blower fan assembly cured my problem. and like shupack said that plastic conduit for the wiring had a few tabs broken off of it during the process. a little more time and patience and i probably could have done it but i had run out of finesse.

one item of note, don't let it go to long like this. the constant pulling of maximum amp draw through the underhood relay box will add lots of heat to this already problematic area. i am sure thats what caused my relay box #7 relay problems.
 

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Premium Member
1995-2002 Range Rover P38A
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1,113 Posts
FANTASTIC! :thumb: Thanks. Looks like I'll be doing the transistor replacement in a few weeks. I'll try to get a few photos and post them with the original posted procedure. Always up for a challenge if it means saving a few bucks!
 
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