All or Nothing Fan? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Russell · 03-11-2005, 01:39 AM

Hey guys!

My 74 just developed an interesting problem this morning. The fan does not come on at all when you just turn on the key, and setting it to medium does nothing as well, but if you set it to high it goes like crazy. Anyone know what I should be looking into as far as fixing it goes?

MylilBowTie · 03-11-2005, 01:50 AM

Blower motor fan? Clutch fan?

badone07 · 03-11-2005, 02:32 AM

if it's the heater/ac blower switch pull the switch and check the positions with an ohm meter.

Mike76251 · 03-11-2005, 07:42 AM

Yeah......what John said,
The high setting is a different circuit than the lower-speed settings so they don't usually go out at the same time.

TrainD5115 · 03-11-2005, 10:15 AM

My old 76 did the same thing Russell and it was the switch. There's only a few more days until Spring so who needs heat anyhow?

ozrulzk5 · 03-11-2005, 10:35 AM

check the blower motor resistor

Russell · 03-11-2005, 10:51 AM

Alright, thanks guys. I'll check the switch this afternoon. I gotta fix it cause today is the last day that I own the 74

As of 4:00 this evening, it will officially be registered and insured by the guy I am selling it to.

cliffsta · 03-11-2005, 12:13 PM

yeah mine is opposite, all positions work except all the way up

**N2TRUX** · 03-11-2005, 12:40 PM

My guess is the switch as well. In the lower settings you normally have resistance to control the speed. On high speed you have direct voltage...

jermasaurus · 03-12-2005, 07:10 PM

Blower Relay? It does make seperate contacts for low/med and high.

**Palf70Step** · 03-12-2005, 10:11 PM

I've never had a switch go on my heater-A/C switches, but also the little springie resistor thingie. It's cheap and normally easy to get to.

Never mind I just remembered your thread in new section and looked at date. Bye Bye 74....

Justins76 · 03-13-2005, 02:01 AM

Mine did the opposite and it was the relay on the blowerbox. $10 at autozone.

Russell · 03-13-2005, 02:10 AM

It wound up that the connection to the resistors was bad, cleaned the contacts up and I had a full range of fan speeds again

03-11-2005, 01:39 AM	#1
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	All or Nothing Fan? Hey guys! My 74 just developed an interesting problem this morning. The fan does not come on at all when you just turn on the key, and setting it to medium does nothing as well, but if you set it to high it goes like crazy. Anyone know what I should be looking into as far as fixing it goes? __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

03-11-2005, 01:50 AM	#2
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	Blower motor fan? Clutch fan? __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI

03-11-2005, 02:32 AM	#3
badone07 Project 2 Resume Join Date: May 2004 Location: Jim Thorpe, PA Posts: 884	if it's the heater/ac blower switch pull the switch and check the positions with an ohm meter. __________________ John 1984 C30 Chevy Crew Cab Dually 1998 Jeep Cherokee 4x4 2004 Chevy Trailblazer 4x4 (wife's) 1970 Mustang FB fully tubed (getting 521 BBF & powerglide) 1978 Nova 2dr (going BBCaddy & S.P. th400) 1984 Monte SS (circle track car)

03-11-2005, 10:15 AM	#5
TrainD5115 North Coast, baby! Join Date: Jun 2004 Location: Toledo, OH Posts: 437	My old 76 did the same thing Russell and it was the switch. There's only a few more days until Spring so who needs heat anyhow? __________________ Brad 79 Scottsdale C20 350/350 3.73's Still running full CA smog gear!

03-11-2005, 10:51 AM	#7
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Alright, thanks guys. I'll check the switch this afternoon. I gotta fix it cause today is the last day that I own the 74 As of 4:00 this evening, it will officially be registered and insured by the guy I am selling it to. __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

03-11-2005, 07:42 AM	#4
Mike76251 Senior Member Join Date: Mar 2003 Posts: 2,500	Yeah......what John said, The high setting is a different circuit than the lower-speed settings so they don't usually go out at the same time.

03-11-2005, 10:35 AM	#6
ozrulzk5 What can I do next ???? Join Date: Jan 2005 Location: Birmingham, Alabama 35126 Posts: 59	check the blower motor resistor

03-11-2005, 12:13 PM	#8
cliffsta Stepsides RULE Join Date: Jul 2004 Location: Pineville, LA Posts: 1,921	yeah mine is opposite, all positions work except all the way up __________________ 1981 Chevy C10 Custom Deluxe Stepside 350 V8, headers, side exhausts, 3-speed auto SOLD 1980 Chevy C10 Custum Deluxe Stepside 305 V8, Edelbrock Performer Intake, Edelbrock 1406 600CFM 4-barrel, TH350C. Bent rod. SOLD 1984 GMC Sierra Classic Longbed 6.2L Diesel SOLD 2009 Kawasaki KLX-250S too many mods for this signature 1999 Honda Accord EX 4-cylinder, 17" Motegi Wheels 215/45/17 Sumitomo tires, Tein S-Tech lowering springs, KYB GR2 shocks, Acura TL 20mm rear swaybar, debadged, blackhoused headlights, Short-Ram Intake Cardomain of the Accord

03-11-2005, 12:40 PM	#9
N2TRUX Happy to be here Join Date: Mar 2000 Location: Cypress, TX Posts: 39,023	My guess is the switch as well. In the lower settings you normally have resistance to control the speed. On high speed you have direct voltage... __________________ Follow me on Facebook and Instagram @N2trux.com Articles- "Jake" the 84 to 74 crewcab "Elwood" the77_Remix 85 GMC Sierra "Scarlett" "Refining Sierra"

03-12-2005, 07:10 PM	#10
jermasaurus Registered User Join Date: Dec 2004 Location: New Lenox, IL Posts: 442	Blower Relay? It does make seperate contacts for low/med and high.

03-12-2005, 10:11 PM	#11
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 46,761	I've never had a switch go on my heater-A/C switches, but also the little springie resistor thingie. It's cheap and normally easy to get to. Never mind I just remembered your thread in new section and looked at date. Bye Bye 74.... __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God! Last edited by Palf70Step; 03-12-2005 at 10:13 PM. Reason: I'm an idiot...

03-13-2005, 02:01 AM	#12
Justins76 OutOfMyMind & I'llNeverKnowWhy Join Date: Apr 2004 Location: Another world, some other time Posts: 672	Mine did the opposite and it was the relay on the blowerbox. $10 at autozone. __________________ -Justin-Out of my mind and I'll never know why 1976 Chevrolet Silverado C10 350 4bbl / TH350 Big10 longbed 1986 Pontiac Firebird T-Top 5.0L TPI 700R4 WS6 1992 Pontiac Firebird T-Top 5.0L TBI 700R4 My cardomain page I don't like to save, it's more fun to spend!!

03-13-2005, 02:10 AM	#13
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	It wound up that the connection to the resistors was bad, cleaned the contacts up and I had a full range of fan speeds again __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)



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