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Author Topic: Heater Blower Failure...resistor?  (Read 7990 times)

Offline DirtyLittleSecret

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Heater Blower Failure...resistor?
« on: January 03, 2009, 10:25:36 pm »
Hey gang, just had my heater blower fail.  Did a search, and did not find anything. 
Replaced the fuse (looked iffy it was so old), and replaced the fan motor to no avail...is there a resistor or something somewhere?  I note what looks like one in line from the fan, but am uncertain.  What else should I check?  Oh, its getting cold again, and I've got a 78 K20 w/ 350.
Much appreciated!
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78 K20: fresh 350, SM465, NP205, 4" Pro Comp, & working hard!
65 Jeep J300: 13.5:1 383, TH400, NP205, mostly NOS. 
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Offline VileZambonie

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Re: Heater Blower Failure...resistor?
« Reply #1 on: January 04, 2009, 08:00:19 am »
78 K20 with or without AC?

Get a test light and go directly to the connection at the fan and see if your test light (alligator clip to a good ground) lights up in any speed with the key on.
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Offline DirtyLittleSecret

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Re: Heater Blower Failure...resistor?
« Reply #2 on: January 04, 2009, 05:43:45 pm »
Sorry about that! W/O AC.  Tested, and found nothing.  Also tested the fan, and it works.  Any other ideas?
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78 K20: fresh 350, SM465, NP205, 4" Pro Comp, & working hard!
65 Jeep J300: 13.5:1 383, TH400, NP205, mostly NOS. 
88 Toylet LandCruiser FJ62: LT1, 4L60e, 3" OME, Aussies.
06 VW TDi: DD@72mpg.

Offline VileZambonie

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Re: Heater Blower Failure...resistor?
« Reply #3 on: January 04, 2009, 07:15:46 pm »
key on engine off do you have B+ at any of the terminals on the resistor at any speeds?
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline DirtyLittleSecret

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Re: Heater Blower Failure...resistor?
« Reply #4 on: January 18, 2009, 11:55:58 pm »
Sorry it took so long, but been gone for work.  Replaced the resistor, and still found nothing.  No power to the resistor.  Any other ideas?  Switch?
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78 K20: fresh 350, SM465, NP205, 4" Pro Comp, & working hard!
65 Jeep J300: 13.5:1 383, TH400, NP205, mostly NOS. 
88 Toylet LandCruiser FJ62: LT1, 4L60e, 3" OME, Aussies.
06 VW TDi: DD@72mpg.

Offline Irish_Alley

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Re: Heater Blower Failure...resistor?
« Reply #5 on: January 19, 2009, 12:29:04 am »
i guess my truck had the same problem due to its always on once you turn the key and always stays on low took the dash off to see what the problem was and saw the resistor switch wasn't even connected was to busy with the keyless entry to even look at how its rigged up
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Offline ccz145a

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Re: Heater Blower Failure...resistor?
« Reply #6 on: January 19, 2009, 08:17:40 am »
Quote
always stays on low
They are supposed to always stay on low, that is not a problem.
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Offline DnStClr

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Re: Heater Blower Failure...resistor?
« Reply #7 on: January 19, 2009, 11:13:17 am »
With the key on you should be getting B+ power at  one of the switch terminals and at one of the resistor terminals like Vile said. If not, recheck the fuse with the test light. If the light comes on at the fuse and not the resistor or switch then the wiring is bad from the fuse. 
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Offline Irish_Alley

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Re: Heater Blower Failure...resistor?
« Reply #8 on: January 19, 2009, 11:11:49 pm »
Quote from: ccz145a on January 19, 2009, 08:17:40 am
Quote
always stays on low
They are supposed to always stay on low, that is not a problem.
even when you switch it to hi?
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Offline ccz145a

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Re: Heater Blower Failure...resistor?
« Reply #9 on: January 20, 2009, 07:56:11 am »
Quote from: Irish_Alley on January 19, 2009, 11:11:49 pm
Quote from: ccz145a on January 19, 2009, 08:17:40 am
Quote
always stays on low
They are supposed to always stay on low, that is not a problem.
even when you switch it to hi?
No, but my point was there is no off.
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1975 C10 Silverado LWB, 454CID, TH400, 10bolt 3.42
11MPG Downhill w/tailwind (but there ain't no hills here)

Offline Irish_Alley

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Re: Heater Blower Failure...resistor?
« Reply #10 on: January 21, 2009, 04:39:22 am »
lol OK i gotcha
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Offline Bubba13

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Re: Heater Blower Failure...resistor?
« Reply #11 on: January 24, 2009, 12:51:21 pm »
did you check the ground wire going to the fan motor. remember it just mounts to fiberglass. if not that , it might be the fan switch on the dash.
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Offline 78 Chevyrado

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Re: Heater Blower Failure...resistor?
« Reply #12 on: January 24, 2009, 06:59:03 pm »
does the fan work when it's set to high?  If yes, it's the resistor or the switch, if no then there's no power or it's the switch.   When on high, the resistor is bypassed and runs direct power.
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Offline DirtyLittleSecret

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Re: Heater Blower Failure...resistor?
« Reply #13 on: January 24, 2009, 07:18:50 pm »
Spent a little time with the tester today, and nothing seemed right.  Finally figured it out though.  Seems I installed two (2) faulty (but new) fuses.  Must have gotten a defective batch of Buss fuses (FYI).  Either way, everything's new and working like a champ!
Thanks for all the help guys!
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78 K20: fresh 350, SM465, NP205, 4" Pro Comp, & working hard!
65 Jeep J300: 13.5:1 383, TH400, NP205, mostly NOS. 
88 Toylet LandCruiser FJ62: LT1, 4L60e, 3" OME, Aussies.
06 VW TDi: DD@72mpg.

Offline DnStClr

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Re: Heater Blower Failure...resistor?
« Reply #14 on: January 26, 2009, 07:43:02 pm »
Good deal. There's nothing like a little heat in January :D
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Don
87 Chevy Silverado
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