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01-06-2006, 07:34 PM | #1 |
Car Knocker
Join Date: May 2001
Location: jefferson,arkansas
Posts: 664
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Blower motor quit
My heater blower motor just quit. Thought I blew a fuse. Checked it out everything ok. Unplugged the wire going to the blower and showing 14.7 volts with engine running and blower switch on high. Thought the motor finally burnt up. Just to be sure I hooked a temp wire from + side of battery to motor and the thing works. Now if I hook up the real wire to the fan and put a multimeter on it the reading is 0, if I unhook the wire and test again 14.7. I'm lost, any ideas.
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68 c-10,91 sportside bed,350 .030 over,4 bolt,10-1 comp,2.05 intake/1.94 exhaust,1.6 Harland Sharp roller rockers,edelbrock rpm cam and intake w/750 carb, 700r4, 3.73 gears,Jacabbs Electronic Igntion w/Accel HEI distributer and super coil. ZR-1 roll pan, filled tailights. Blazer tank. Hidden hitch. 2 1/2" Flowmaster 40's. Parts bought but not installed>> ford 9" posi with disc. CCP front and rear lowering kit 4/5. Cab corners,foor boards,rockers, cab braces, Phatom grill, Painless wiring kit. |
01-06-2006, 07:41 PM | #2 |
Registered User
Join Date: Dec 2000
Location: Gresham, OR, USA
Posts: 106
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Re: Blower motor quit
Look to see if your resistor pack is bad. I don't remember if the motor is switched on the ground side or the power side.
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72 GMC K20, 454, TH350 00 GMC Yukon 66 Ford Bronco |
01-06-2006, 08:45 PM | #3 |
Car Knocker
Join Date: May 2001
Location: jefferson,arkansas
Posts: 664
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Re: Blower motor quit
I checked the resister (sp), voltage goes up as I come up on fan speeds. I'm pretty sure it is + switched. Will probably go get a fan motor but trying to figure out why it works when wired direct and wipes out all my voltage when plugged up through the factory harness.
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68 c-10,91 sportside bed,350 .030 over,4 bolt,10-1 comp,2.05 intake/1.94 exhaust,1.6 Harland Sharp roller rockers,edelbrock rpm cam and intake w/750 carb, 700r4, 3.73 gears,Jacabbs Electronic Igntion w/Accel HEI distributer and super coil. ZR-1 roll pan, filled tailights. Blazer tank. Hidden hitch. 2 1/2" Flowmaster 40's. Parts bought but not installed>> ford 9" posi with disc. CCP front and rear lowering kit 4/5. Cab corners,foor boards,rockers, cab braces, Phatom grill, Painless wiring kit. |
01-06-2006, 09:27 PM | #4 |
yeeha
Join Date: Sep 2005
Location: Sherwood Park & Fort McMurray, Alberta
Posts: 72
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Re: Blower motor quit
yepper, sounds like the resistor pack .... just a *note* i do believe that there is a fuse in that resistor pack for low and for Medium, high speed is just straight supply power and has a NO resistor and therefore connected after fuse in the resistor pack. i'd suggest to replace the pack and all should be good .... but if she craps out again well then you need to look at the blower motor. It's got too much fricton to turn freely and is therefore drawing too many amps and blowing the small fuse in the pack.
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1969 GMC 910 97% rust free 2002 olds Alero 1986 New Yorker 4dr ... the new DD...My POS car... dude its got a turbo!!! Don't drink and drive, you might spill something!!! Daryl Kuchmak |
01-07-2006, 06:59 AM | #5 |
Senior Member
Join Date: Dec 2002
Location: Portland, Oregon
Posts: 901
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Re: Blower motor quit
according to the wiring diagram I have; the 'high' speed blower motor switch setting goes thru a relay. This relay is located on the inside of cab, right side, up alongside the glove compartment box............ Jim
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'71 GMC;fleetside;PB/PS/AC/CC/402 Eng./Custom Paint/110,000act miles/3 fuel tanks(52gal). |
01-07-2006, 09:55 AM | #6 |
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Join Date: Sep 2005
Location: Monroe, WA
Posts: 3,815
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Re: Blower motor quit
I have a blower that runs, but on low only. I was planning on replacing the switch just as a "let's replace this and see what happens" thing...should I be looking at the resistor pack and/or relay instead?
I'm definitely not an auto electric whiz |
01-07-2006, 12:44 PM | #7 |
Registered User
Join Date: Dec 2000
Location: Gresham, OR, USA
Posts: 106
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Re: Blower motor quit
Jay6891 - it's definitely not the motor if you can get it to run direct wired.
Billa - if you have low speed, you're resistor pack is OK. I'd check the switch/switch wiring. GMCJim - are you sure you have the right year diagram? I have a 72GMC with no relay on the firewall. It's direct wired thru the switch on mine.
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72 GMC K20, 454, TH350 00 GMC Yukon 66 Ford Bronco |
01-07-2006, 07:16 PM | #8 |
Senior Member
Join Date: Dec 2002
Location: Portland, Oregon
Posts: 901
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Re: Blower motor quit
Craig S.... My '71 GMC with factory air does have the relay ( I have replaced it!) Looks like trucks without air did not use the relay.... Also the standard fan used with heater only trucks draws 6.25 amps max ( 2550 - 2950 RPM).
The standard blower motor used with factory air draws 16.5 amps max ( 3700 RPM ) . Recalling previous messages regarding heater/air blower switch malfunctions; it appears that if the heavy duty ( air-cond) blower is used with the heater only installations, the amperage could damage the blower switch unless a relay was installed for the 'high' blower function. ( just my 2 cents ! ).............. Jim
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'71 GMC;fleetside;PB/PS/AC/CC/402 Eng./Custom Paint/110,000act miles/3 fuel tanks(52gal). |
01-07-2006, 07:29 PM | #9 |
Watch out for your cornhole !
Join Date: Jun 2003
Location: Azle, Texas
Posts: 14,162
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Re: Blower motor quit
I've seen before, where a switch will pass enough current to light a test light or show full voltage, but not enough amperage to work the fan.
Jumper the switch itself and I bet you'l find the motor runs.
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01-07-2006, 08:38 PM | #10 |
Car Knocker
Join Date: May 2001
Location: jefferson,arkansas
Posts: 664
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Re: Blower motor quit
I was thinking of that today at work today Tx Firefighter. Took the switch apart and cleaned it and polished up the copper contacts. Not much to the switch though gotta love 1968 tech. Still same result. Anybody know which fuse it is in the fuse box. Can't read the writing anymore. Maybe losing the amperage in the fuse box contacts.
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68 c-10,91 sportside bed,350 .030 over,4 bolt,10-1 comp,2.05 intake/1.94 exhaust,1.6 Harland Sharp roller rockers,edelbrock rpm cam and intake w/750 carb, 700r4, 3.73 gears,Jacabbs Electronic Igntion w/Accel HEI distributer and super coil. ZR-1 roll pan, filled tailights. Blazer tank. Hidden hitch. 2 1/2" Flowmaster 40's. Parts bought but not installed>> ford 9" posi with disc. CCP front and rear lowering kit 4/5. Cab corners,foor boards,rockers, cab braces, Phatom grill, Painless wiring kit. |
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