blower motor: no high speed - The 1947 - Present Chevrolet & GMC Truck Message Board Network

4x4Bowhunter · 01-13-2005, 09:13 PM

have a 68 chevy w/ air. high speed on the fan will not work. i have replaced the switch w/out any luck. i konw the motor obviously works b/c it works fine on all the other settings.

anyone encounter this before?

**72CHEVYBLAZER** · 01-13-2005, 09:28 PM

check the resistor

mblackburnjr · 01-13-2005, 09:34 PM

I know this is dumb,but sometimes its something simple...Did you check to make sure the cable was adjusted to work all speeds when you replaced the switch?....ask me how i know!

4x4Bowhunter · 01-13-2005, 09:56 PM

im pretty sure all the cables are working correctly. all the doors move correctly.
which cable needs adjusting?
i unhooked the wiring harness from the switch and plugged in a new switch...same results...no high speed. there werent any cables to fuss with so i may require some 'splaining...

and where is the resistor located?

Thanks!!

teamharvey · 01-13-2005, 09:57 PM

Quote:

Originally Posted by 72CHEVYBLAZER

check the resistor

Yep !.....I went through this same problem and it was the resistor.

4x4Bowhunter · 01-13-2005, 09:57 PM

where would the resistor be located?

Longhorn Man · 01-13-2005, 10:29 PM

Most likely it'll be the relay.

Huck · 01-13-2005, 10:42 PM

There is a relay located screwed to the outside of the heater box. It is located under/behind the glove box between the heater and the pass side firewall. Believe there are like 3-4 wires attached to this relay via a plug connection. This realy can go bad and when it does, you loose high speed on the fan motor. You also need to make sure this relay has a good ground. This is not a unusual problem on to A/C trucks.

4x4Bowhunter · 01-13-2005, 10:52 PM

Are the relay and the resistor the same thing y'all are talking about?

I found the relay, located behind the glovebox (tore it up pretty good...brittle as candy) between the plenum and the kickpanel.

But havent found any resistor...or are they the same thing?

Longhorn Man · 01-13-2005, 10:57 PM

no, not the same. look for a plug that goes into the heater box...it is somewhere under the dash, i think in the same area as the relay.

jhow66 · 01-13-2005, 11:27 PM

Also check at fuse panel where orange wire from relay connects to the large red. This connection is prone to heating up (from being loose) and causing a bad joint. One way to check is to turn switch on and take a test light and touch to the orange wire at relay.

GMC Jim · 01-14-2005, 03:27 AM

The high speed is controlled by the relay ( mentioned by others in the above messages). The resistor pack is for the lower speeds..

400ex · 01-14-2005, 09:28 AM

I agree with Huck. I had this exact problem on my '71 w/ac. I replaced the switch; no high speed. Then I replaced the relay on the side of the glove box; still no high speed. Out of frustration I regrounded the relay on the glove box to the frame and bingo... High speed works.

Moral.. Check the simple things.. In my case I had a bad ground on the relay. Didn't need a new switch or relay.

James

chickenwing · 01-14-2005, 10:04 AM

The relay uses a bonding strap for the ground. The bonding strap is connected to the relay with a screw to the relay mount. The screw tends to back out because it is screwed into the plastic a/c case. Simple fix is to just get a bigger screw. Probably run another 30 years. I switched to a differant relay that has a regular ground connection and installed the ground to the firewall. This is the relay I used. http://www.partsamerica.com/PartDeta...artNumber=AC12

flip66 · 01-14-2005, 07:24 PM

had the same problew it was the relay 12.00 at auto zone.

dwaite72lnghrn · 01-14-2005, 08:06 PM

It's the relay on the inside passenger side of the heater/AC box. 2 screws 5/16 I think. The resistor comes in the left side top through a gromet and the relay is right side across from the vacuum hose on the server for the kick panel.

4x4Bowhunter · 01-14-2005, 11:19 PM

Thanks folks!!

i pulled the relay out and actually took it apart. it appears that about 30 years worth of water had settled into the part. since it actually mounts upside down, it "collected" that water and rusted everything!! taking it apart, i actually jumped the relay arm with the non-rusted-together terminal, and low and behold, HIGH SPEED!
i was going to bend the rusted parts together, but then you dont have any other speed, only high.
CMC Jim was correct: the relay is for high speed, while the resistor is for low.
just for grins, i did check the resistor and it was fine.

i want to thank everyone who contributed and helped me out! THANK YOU!!

01-13-2005, 09:13 PM	#1
4x4Bowhunter Registered User Join Date: Jan 2005 Location: Denver, CO Posts: 110	blower motor: no high speed have a 68 chevy w/ air. high speed on the fan will not work. i have replaced the switch w/out any luck. i konw the motor obviously works b/c it works fine on all the other settings. anyone encounter this before?

01-13-2005, 11:27 PM	#11
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	Also check at fuse panel where orange wire from relay connects to the large red. This connection is prone to heating up (from being loose) and causing a bad joint. One way to check is to turn switch on and take a test light and touch to the orange wire at relay. __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

01-14-2005, 03:27 AM	#12
GMC Jim Senior Member Join Date: Dec 2002 Location: Portland, Oregon Posts: 901	The high speed is controlled by the relay ( mentioned by others in the above messages). The resistor pack is for the lower speeds.. __________________ '71 GMC;fleetside;PB/PS/AC/CC/402 Eng./Custom Paint/110,000act miles/3 fuel tanks(52gal).

01-14-2005, 09:28 AM	#13
400ex Registered User Join Date: Jan 2003 Location: Damon, Tx Posts: 56	No high speed I agree with Huck. I had this exact problem on my '71 w/ac. I replaced the switch; no high speed. Then I replaced the relay on the side of the glove box; still no high speed. Out of frustration I regrounded the relay on the glove box to the frame and bingo... High speed works. Moral.. Check the simple things.. In my case I had a bad ground on the relay. Didn't need a new switch or relay. James

01-14-2005, 10:04 AM	#14
chickenwing Lovin' Life in Miss.! Join Date: Mar 2004 Location: Puckett, Mississippi Posts: 1,937	The relay uses a bonding strap for the ground. The bonding strap is connected to the relay with a screw to the relay mount. The screw tends to back out because it is screwed into the plastic a/c case. Simple fix is to just get a bigger screw. Probably run another 30 years. I switched to a differant relay that has a regular ground connection and installed the ground to the firewall. This is the relay I used. http://www.partsamerica.com/PartDeta...artNumber=AC12 __________________ The truck... you hear that? No really, you did hear that?!!! Last edited by chickenwing; 01-14-2005 at 10:06 AM.

01-13-2005, 09:28 PM	#2
72CHEVYBLAZER Junior Member Join Date: Oct 2004 Location: IDAHO Posts: 46	check the resistor

01-13-2005, 09:34 PM	#3
mblackburnjr collector of vintage rust Join Date: Apr 2004 Location: southern ohio Posts: 421	I know this is dumb,but sometimes its something simple...Did you check to make sure the cable was adjusted to work all speeds when you replaced the switch?....ask me how i know!

01-13-2005, 09:56 PM	#4
4x4Bowhunter Registered User Join Date: Jan 2005 Location: Denver, CO Posts: 110	im pretty sure all the cables are working correctly. all the doors move correctly. which cable needs adjusting? i unhooked the wiring harness from the switch and plugged in a new switch...same results...no high speed. there werent any cables to fuss with so i may require some 'splaining... and where is the resistor located? Thanks!!

01-13-2005, 09:57 PM	#6
4x4Bowhunter Registered User Join Date: Jan 2005 Location: Denver, CO Posts: 110	where would the resistor be located?

01-13-2005, 10:29 PM	#7
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Most likely it'll be the relay.

01-13-2005, 10:42 PM	#8
Huck Senior Member Join Date: Jun 2001 Location: Shelbyville, KY Posts: 3,261	There is a relay located screwed to the outside of the heater box. It is located under/behind the glove box between the heater and the pass side firewall. Believe there are like 3-4 wires attached to this relay via a plug connection. This realy can go bad and when it does, you loose high speed on the fan motor. You also need to make sure this relay has a good ground. This is not a unusual problem on to A/C trucks.

01-13-2005, 10:52 PM	#9
4x4Bowhunter Registered User Join Date: Jan 2005 Location: Denver, CO Posts: 110	Are the relay and the resistor the same thing y'all are talking about? I found the relay, located behind the glovebox (tore it up pretty good...brittle as candy) between the plenum and the kickpanel. But havent found any resistor...or are they the same thing?

01-13-2005, 10:57 PM	#10
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	no, not the same. look for a plug that goes into the heater box...it is somewhere under the dash, i think in the same area as the relay.

01-14-2005, 07:24 PM	#15
flip66 Registered User Join Date: Jan 2004 Location: Garland TX Dallas area Posts: 658	had the same problew it was the relay 12.00 at auto zone. __________________ 1998 Pontiac Grad Prix GTP 1969 C10 396 TH400 3.08 posi

01-14-2005, 08:06 PM	#16
dwaite72lnghrn Registered User Join Date: Jun 2002 Location: central pa Posts: 1,525	It's the relay on the inside passenger side of the heater/AC box. 2 screws 5/16 I think. The resistor comes in the left side top through a gromet and the relay is right side across from the vacuum hose on the server for the kick panel. __________________ 72 longhorn c30 502BB/th400/fact air/4.11rear/ custom camper 72 bug(the better half's) under reconstruction 2009 HHR aqua blue 71 GMC k20 350/sm465 2009 Chevy hd3500 6.6 Victory Red crew cab dually Dave & Jeanne



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01-14-2005, 11:19 PM	#17
4x4Bowhunter Registered User Join Date: Jan 2005 Location: Denver, CO Posts: 110	Thanks folks!! i pulled the relay out and actually took it apart. it appears that about 30 years worth of water had settled into the part. since it actually mounts upside down, it "collected" that water and rusted everything!! taking it apart, i actually jumped the relay arm with the non-rusted-together terminal, and low and behold, HIGH SPEED! i was going to bend the rusted parts together, but then you dont have any other speed, only high. CMC Jim was correct: the relay is for high speed, while the resistor is for low. just for grins, i did check the resistor and it was fine. i want to thank everyone who contributed and helped me out! THANK YOU!!

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