fan switch on HI setting -not working - The 1947 - Present Chevrolet & GMC Truck Message Board Network

into69z · 02-02-2011, 01:32 PM

This has happened before but I can't remember what caused it-my fan switch works on all speeds except hi-I have a 69 with a/c - I think I replaced the switch last time but that was not the problem-I know someone has the answer-

BLACK AND BLUE 67-72 · 02-02-2011, 02:25 PM

It's probably your blower resistor.

jbclassix · 02-02-2011, 02:30 PM

Don't they have a relay for high? I just fixed that problem on my 91 (I know, different truck...)My fan relay was bad. But I thought they had a resistor mounted inside the duct and a relay on the outside

mikemileski · 02-02-2011, 02:33 PM

It is most likely the blower fan relay. When I bought my '72 GMC with factory air, it only worked on low and medium. I was going to replace the switch and somebody told me that it was most likely the relay. I bought a new one for $15, installed it and now it blows on high. I think I read somewhere that low and medium just go through the switch but they route the high speed (read high amps) wiring through the relay. It's located behind the right side of glovebox, high up near the firewall.

Mike Mileski
Tucson, AZ

crm318 · 02-02-2011, 02:38 PM

Where might you find on of these relays?

**LockDoc** · 02-02-2011, 02:41 PM

With A/C has a relay, heater only doesn't...

First pic is heater only, second is w/air.

LockDoc

mikemileski · 02-02-2011, 02:44 PM

The relays can be found at any auto parts store.

Mike Mileski
Tucson, AZ

Wrenchbender Ret · 02-02-2011, 04:40 PM

Some of them have an inline fuse. It might be on the engine side of the fire wall at the junction block. It caries a lot of current & often the fuse holder its self gets burnt.

into69z · 02-02-2011, 04:51 PM

thanks guys-I knew you would know the answer-I'll get to fixing it. Steve

02-02-2011, 01:32 PM	#1
into69z "brand new second-hand" Join Date: Feb 2007 Location: White House, Tennessee Posts: 526	fan switch on HI setting -not working This has happened before but I can't remember what caused it-my fan switch works on all speeds except hi-I have a 69 with a/c - I think I replaced the switch last time but that was not the problem-I know someone has the answer- __________________ Steve 69 3/4t custom camper tilt,am/fm,speed warning,air gauge,buddy buckets,aux battery, big block,p/s,p/b,a/c 67 Camaro 96 Impala ss-sold 04 hybrid Honda-saving gas for the blue truck!:b69:

02-02-2011, 02:25 PM	#2
BLACK AND BLUE 67-72 Firefighter Join Date: Feb 2001 Location: Yellville, Ar, USA Posts: 1,943	Re: fan switch on HI setting -not working It's probably your blower resistor. __________________ '72 Chevy SWB 350 Auto '67 GMC LWB 350 4 speed '70 Chevy 4x4 Stepside 350 Auto Yellville, Ar. USA

02-02-2011, 02:30 PM	#3
jbclassix Junk Yartist Join Date: Jul 2009 Location: Greeley, CO Posts: 2,203	Re: fan switch on HI setting -not working Don't they have a relay for high? I just fixed that problem on my 91 (I know, different truck...)My fan relay was bad. But I thought they had a resistor mounted inside the duct and a relay on the outside __________________ -Jeremy YOU ONLY FAIL IF YOU STOP TRYING 70 Crew Cab Build Link 70 GMC Suburban 4X4 build thread 95 Yukon Daily Driver Rebuilding an NP205

02-02-2011, 02:33 PM	#4
mikemileski Registered User Join Date: Jul 2009 Location: Tucson, AZ Posts: 66	Re: fan switch on HI setting -not working It is most likely the blower fan relay. When I bought my '72 GMC with factory air, it only worked on low and medium. I was going to replace the switch and somebody told me that it was most likely the relay. I bought a new one for $15, installed it and now it blows on high. I think I read somewhere that low and medium just go through the switch but they route the high speed (read high amps) wiring through the relay. It's located behind the right side of glovebox, high up near the firewall. Mike Mileski Tucson, AZ

02-02-2011, 02:38 PM	#5
crm318 Alright Alright Alright Join Date: Mar 2004 Location: Midland, Texas Posts: 1,672	Re: fan switch on HI setting -not working Where might you find on of these relays? __________________ 1972 Cheyenne Chevrolet red and white 357ci, Vortec heads, GM Performance high rise intake, Comp 268H .454/.454 218/218 110 LSA Quadrajet carb, Flowtech headers, 2.25 40 series HEI, Curve kit, TH 350, 3.07 gears 275/60/15s on 15x8 rallies

02-02-2011, 02:41 PM	#6
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,648	Re: fan switch on HI setting -not working With A/C has a relay, heater only doesn't... First pic is heater only, second is w/air. LockDoc Attached Images __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 -

02-02-2011, 02:44 PM	#7
mikemileski Registered User Join Date: Jul 2009 Location: Tucson, AZ Posts: 66	Re: fan switch on HI setting -not working The relays can be found at any auto parts store. Mike Mileski Tucson, AZ

02-02-2011, 04:40 PM	#8
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,228	Re: fan switch on HI setting -not working Some of them have an inline fuse. It might be on the engine side of the fire wall at the junction block. It caries a lot of current & often the fuse holder its self gets burnt.

02-02-2011, 04:51 PM	#9
into69z "brand new second-hand" Join Date: Feb 2007 Location: White House, Tennessee Posts: 526	Re: fan switch on HI setting -not working thanks guys-I knew you would know the answer-I'll get to fixing it. Steve __________________ Steve 69 3/4t custom camper tilt,am/fm,speed warning,air gauge,buddy buckets,aux battery, big block,p/s,p/b,a/c 67 Camaro 96 Impala ss-sold 04 hybrid Honda-saving gas for the blue truck!:b69:



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