After reading several posts on remedies for low speed blower
problems, I have the blower out of the vehicle and have checked the
relays (good) and motor (also good). My question is, What is the
darlington transistor and where is it found? I can see a black
aluminum rectangle sandwiching a simple circuit board, that is
riveted to the side of the blower housing. Is this it? How do you
check it? I’ve checked the rotary switch on the center console and
it looks and feels fine. Can anyone help?
Thanks.–
1989 XJ40, 79,000 miles
Rancho Cucamonga CA, United States
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I would suggest replacing the relays. One sees heavy current and by now the
contacts must be about to give in on your car.
If you have lost medium and low blower speeds, the Darlington is bad,
otherwise it’s OK and you can leave it alone.
You should also service the blower motor and brushes as outlined in the
online book, otherwise you could be back in there sooner than you want.
David Hurlston
ViaData LP
Sugar Land, Texas-----Original Message-----
After reading several posts on remedies for low speed blower
problems, I have the blower out of the vehicle and have checked the
relays (good) and motor (also good). My question is, What is the
darlington transistor and where is it found? I can see a black
aluminum rectangle sandwiching a simple circuit board, that is
riveted to the side of the blower housing. Is this it? How do you
check it? I’ve checked the rotary switch on the center console and
it looks and feels fine. Can anyone help?
Thanks.
1989 XJ40, 79,000 miles
Rancho Cucamonga CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting
services and resources including Photo Albums, Event Diary / Calendar, On
Line Books and more !
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In reply to a message from Bryan N sent Sun 13 Aug 2006:
Thanks to Bryan N and David Hurlston for their information.
Truly
Hot August
Dean Colley–
1989 XJ40, 79,000 miles
Rancho Cucamonga CA, United States
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In reply to a message from David Hurlston sent Sun 13 Aug 2006:
I’ve replaced the darlington transistor and associated resistors.
I’ve replaced a bad relay with diode in the same blower housing
(other was like new). I plug the thing in for a test (large round
plug, 2-prong, and the small multi-wire connector and nothing. The
fan blows fine when I hook it to 12V on the bench. Do these units
have to grounded somewhere to run hooked to the 2 harnesses? Is the
large 2-prong plug the voltage source to run the blower? Please
help. I’m sweating in the heat. Thanks–
The original message included these comments:
After reading several posts on remedies for low speed blower
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The two pin connector is power to the blower assy. Black is ground, brown is
hot all the time. My problem was a bad solder joint on the circuit board behind
the fuse block, as I wrote the other day. It’s not easy, but you have to check
the voltage into the blower when it’s engaged to run. I made up a couple of
short jumpers with spade terminals to bypass the relays. I merely removed the
relays, and plugged the jumpers into the relay sockets where the heavy wires
connect. Plug it into the car, and the blower should run on high. If not,
check the voltage at the relay bypass jumpers. The brown wire relay jumper
should have 12v, and the other relay jumper should measure 0 volts to ground.
Spade terminals can be had at Ace or other local hardware. Take a relay for
sample if you’re not sure.
The 7 pin connector has wires that control the relays and the low and med speeds
through the transistor.
rdr
Dean lamented: I’ve replaced the darlington transistor and associated
resistors.
I’ve replaced a bad relay with diode in the same blower housing
(other was like new). I plug the thing in for a test (large round
plug, 2-prong, and the small multi-wire connector and nothing. The
fan blows fine when I hook it to 12V on the bench. Do these units
have to grounded somewhere to run hooked to the 2 harnesses? Is the
large 2-prong plug the voltage source to run the blower? Please
help. I’m sweating in the heat. Thanks
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In reply to a message from HotAugust sent Tue 5 Sep 2006:
I was swearing after doing the same, putting it back in and then
having little success.
I did it again and found the darlington mounting screws (and nuts)
had a film of corrosion that prevented a good connection to the
case. Sanded them down and I was off to the races.
Tom–
The original message included these comments:
I’ve replaced the darlington transistor and associated resistors.
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In reply to a message from Ralph Ricks sent Wed 6 Sep 2006:
Gentlemen,
After re-soldering the fuse boxes, re-soldering in all new
components of the the fan speed control, including the Darlington
resistor, buying 3 other fan units from junk yards, and countless
hours…I am pleased to announce I found the problem. The center
console fan control had loose screws and prevented the contacts
from sending a signal to the blower at low speeds. This repair took
only 20 minutes and was very easy. Please…Check this out before
you start the tedious work of removing and repairing an air
conditioning blower fan. 11 hours later, in some of the hotest
temps of the summer, I got it fixed. Start with the simple
stuff…And never…ever…give up! Thanks to all who had the balls
to reply to my post. You are what make this site happen.
Dean Colley–
The original message included these comments:
Dean lamented: I’ve replaced the darlington transistor and associated
help. I’m sweating in the heat. Thanks
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