Heater blower need help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

BCOWANWHEELS · 09-14-2018, 01:01 AM

My 72 c10 with a/c only has low speed on the blower. Just replaced the blower motor, same results. What should i do next. Never worked on a/c equiped truck before. All help is appreciated a bunch............
Thanks
bob

Hutch · 09-14-2018, 01:25 AM

BCOWANWHEELS
Check the ground wire from the relay inside the cab on the firewall.
It is very short
It is located up high between the glove box and passenger side wall.

There is a short ground wire that is supposed to go one of the shroud bolts that come through the firewall
Easy test is to attach a short piece of wire while it is on high from the relay to ground.

A lot of folks do not get the ground re-attached correctly while working on the heater coil.

The symptoms are
Low= Low
Medium= Medium
High = Very SLow

BCOWANWHEELS · 09-14-2018, 01:51 AM

I havent got nothing but low speed. Even with oem blower motor

rockyrivermark · 09-14-2018, 10:53 AM

I'm not sure but do our trucks some a blower motor resistor? we know thats a very common problem on later models when one or more of the variable speeds go out.

isn't there something like a resistor that by the fan switch?

edit:
just looked it up.
this is what you need. it's mounted to the back of the fan control area i believe
https://www.classicparts.com/1960-72...iABEgLjq_D_BwE

BCOWANWHEELS · 09-14-2018, 01:30 PM

I bet thats it, could somebody tell me exactly where its located. I,am crippled and movement is real tough for me.
Bob

**clay68c10** · 09-14-2018, 03:31 PM

Maybe the resistor, but I'd suspect a bad switch first. Hi doesn't go thru the resistor, but low does. The switch is easy to get to and test. No sense spending money without a quick continuity test of the switch.

BCOWANWHEELS · 09-14-2018, 03:38 PM

Resistor is 10.00 at oreillys, i,ll check switch also. Thanks.

Andy4639 · 09-14-2018, 04:09 PM

Here are some good info pages.
Most times on a AC truck it's the switch. It's a easy fix. I have fixed many of them by taking them a part and cleaning the contacts and regreasing them. A lot of times it's the plastic connector gets hot and melts and the terminals want make contact also.

This shows you where everything is.

BCOWANWHEELS · 09-14-2018, 07:09 PM

perfect............ you blessed me tremendously.......... thanks bunches

Andy4639 · 09-14-2018, 07:11 PM

Quote:

Originally Posted by BCOWANWHEELS

perfect............ you blessed me tremendously.......... thanks bunches

Your welcome.

09-14-2018, 01:01 AM	#1
BCOWANWHEELS Registered User Join Date: Nov 2006 Location: KINGSPORT,TN. Posts: 3,035	Heater blower need help My 72 c10 with a/c only has low speed on the blower. Just replaced the blower motor, same results. What should i do next. Never worked on a/c equiped truck before. All help is appreciated a bunch............ Thanks bob __________________ I BELIEVE IN JOHN 3:16

09-14-2018, 01:25 AM	#2
Hutch Registered User Join Date: Oct 2001 Location: Grapevine, Tx. Posts: 2,142	Re: Heater blower need help BCOWANWHEELS Check the ground wire from the relay inside the cab on the firewall. It is very short It is located up high between the glove box and passenger side wall. There is a short ground wire that is supposed to go one of the shroud bolts that come through the firewall Easy test is to attach a short piece of wire while it is on high from the relay to ground. A lot of folks do not get the ground re-attached correctly while working on the heater coil. The symptoms are Low= Low Medium= Medium High = Very SLow __________________ John Hutchison Grapevine,Texas 68 1/2 t swb 68 Mustang 69 Jaguar 71 1/2 t swb 88 Supra CompTs6m 93 Escort GT 2005 Corolla XRS

09-14-2018, 01:51 AM	#3
BCOWANWHEELS Registered User Join Date: Nov 2006 Location: KINGSPORT,TN. Posts: 3,035	Re: Heater blower need help I havent got nothing but low speed. Even with oem blower motor __________________ I BELIEVE IN JOHN 3:16

09-14-2018, 10:53 AM	#4
rockyrivermark Registered User Join Date: Apr 2011 Location: Fairview Park, Ohio Posts: 1,031	Re: Heater blower need help I'm not sure but do our trucks some a blower motor resistor? we know thats a very common problem on later models when one or more of the variable speeds go out. isn't there something like a resistor that by the fan switch? edit: just looked it up. this is what you need. it's mounted to the back of the fan control area i believe https://www.classicparts.com/1960-72...iABEgLjq_D_BwE __________________ My build page http://67-72chevytrucks.com/vboard/s...d.php?t=764662 My cabinet building site http://www.cbcabinets.com

09-14-2018, 01:30 PM	#5
BCOWANWHEELS Registered User Join Date: Nov 2006 Location: KINGSPORT,TN. Posts: 3,035	Re: Heater blower need help I bet thats it, could somebody tell me exactly where its located. I,am crippled and movement is real tough for me. Bob __________________ I BELIEVE IN JOHN 3:16

09-14-2018, 03:31 PM	#6
clay68c10 Senior Member Join Date: Aug 2004 Location: Centennial, CO Posts: 2,987	Re: Heater blower need help Maybe the resistor, but I'd suspect a bad switch first. Hi doesn't go thru the resistor, but low does. The switch is easy to get to and test. No sense spending money without a quick continuity test of the switch. __________________ ClusterTruck: 68 C10 Bought in 89, wrecked in 03. Slow low $ rebuild started '17. 6.0 & TKO http://67-72chevytrucks.com/vboard/s...d.php?t=788602 93 K1500 Short Step, 350, NV4500, EBL flash ECU. Vortec heads & roller cam someday... 05 Jeep Wrangler Unlimited. 3” lift & 6-speed 02 E320 the insurance total “free car” 13 Tahoe LTZ

09-14-2018, 03:38 PM	#7
BCOWANWHEELS Registered User Join Date: Nov 2006 Location: KINGSPORT,TN. Posts: 3,035	Re: Heater blower need help Resistor is 10.00 at oreillys, i,ll check switch also. Thanks. __________________ I BELIEVE IN JOHN 3:16

09-14-2018, 04:09 PM	#8
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: Heater blower need help Here are some good info pages. Most times on a AC truck it's the switch. It's a easy fix. I have fixed many of them by taking them a part and cleaning the contacts and regreasing them. A lot of times it's the plastic connector gets hot and melts and the terminals want make contact also. This shows you where everything is. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

09-14-2018, 07:09 PM	#9
BCOWANWHEELS Registered User Join Date: Nov 2006 Location: KINGSPORT,TN. Posts: 3,035	Re: Heater blower need help perfect............ you blessed me tremendously.......... thanks bunches __________________ I BELIEVE IN JOHN 3:16



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