1997 Pontiac Grand Prix Blower motor works on high only som

Tiny
GARBE
  • MEMBER
  • 1997 PONTIAC GRAND PRIX
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 130,000 MILES
The motor only runs on High (5) but even then it takes 20-15 seconds or more to start. It will not run on other speeds at all however earlier on, it would run on slower speeds but only after driving for quite a while.
I've tried a new motor with same strange results. The resistor module seems OK because I find around 12 volts at blower wires on High as well as the lower speeds ! The relay clicks when turning the blower switch on but when in High, the relay returns to "off" or at least to same condition as when switch is off.
I'm an electronics tech but have no diagram for the involvement of the relay side. I see two other relays and a couple of IC's on the same printed circuit board.
What may be the cause of this situation? Thanks!
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Sunday, October 26th, 2008 AT 3:15 PM

3 Replies

Tiny
RASMATAZ
  • MEMBER
Hi Garbe and welcome to 2carpros

Below is your blower motor circuit


http://www.2carpros.com/forum/automotive_pictures/12900_hvac1_2.jpg



http://www.2carpros.com/forum/automotive_pictures/12900_hvac2_2.jpg



http://www.2carpros.com/forum/automotive_pictures/12900_hvac3_1.jpg



http://www.2carpros.com/forum/automotive_pictures/12900_hvac4_1.jpg

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Sunday, October 26th, 2008 AT 3:38 PM
Tiny
GARBE
  • MEMBER
Thanks very much. I already have that wiring diagram. Further troubleshooting has confirmed the motor, resistor block and high speed relay plus the fan switch are all in perfect working order.
I found that the voltage at the input to the blower switch reads low. Around only 5 volts! I tracked down the fuse (top left on on diagram) and found the voltage was low right at the
supply side of the fuse. I bridged across from the adjacent fuse (from another supply lead) to the blower motor circuit and all works perfectly!
If you pull the blower motor fuse, you may read the full battery voltage at the supply side but as soon as you install the fuse and turn the fan switch on, the voltage drops to a very low level or practically zero.
There are two small gauge pink wires supplying this fuse. I haven't tried to track them back since they are so buried in a cable bundle behind the dash. Would you know or have a diagram of where they come from?
Apparently there is a break/corrosion or high resistance buildup in the feed wire or a partial short to ground. Also wondering if this path would lead back to the ignition switch and if the problem could originate in the switch. Burned or oxidized connections.
Seems like only about a 18-22 gauge wire is used and same with the brown wire from the fuse to the motor switch. Doesn't appear to be very heavy for a rather high current draw from a motor.
Anyway if I knew where this questionable pair of pink wires goes. Physically. So as to know what to check next would help. Right now I am not sure how this pair of wires ties into the battery positive side.
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Wednesday, October 29th, 2008 AT 10:18 PM
Tiny
RASMATAZ
  • MEMBER
Try below EWD


http://www.2carpros.com/forum/automotive_pictures/12900_hl_fuse_60_1.jpg




http://www.2carpros.com/forum/automotive_pictures/12900_hl_fuse2_1.jpg




http://www.2carpros.com/forum/automotive_pictures/12900_hl_fuse3_1.jpg

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Thursday, October 30th, 2008 AT 12:27 PM

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