Help! How can I get my heater fan to stop running???? - Page 3 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

kna4977 · 09-19-2006, 08:01 PM

Quote:

Originally Posted by jhow66

Here is how mine is wired:

Hey, thanks for taking the time to do that for me. It seems to have helped a lot, although I'm still not quite there. So I took the relay wires out of the harness and tried a lot of different scenarios as listed above. I then put the wires back into the positions shown in the picture, and although it doesn't look any different than what I started with, it must be.

Now high fan is high fan, and the fan doesn't blow immediately when I connect the battery like before, but every other position (off,low, medium) is off. Any suggestions?

I'm taking it in tomorrow to have it charged, and will most likely let them fix it, but I would still like to know what is wrong.

Thanks again for your help!

mrein3 · 09-19-2006, 10:02 PM

Check the voltage before and after the resistor block with the fan on medium and low. You may have fried those resistors.

jhow66 · 09-19-2006, 10:21 PM

Did you check the resistor when you were installing the AC-was it plugged up? Sounds like what Mrein' says.

kna4977 · 09-20-2006, 06:52 PM

Quote:

Originally Posted by jhow66

Did you check the resistor when you were installing the AC-was it plugged up? Sounds like what Mrein' says.

Yes I checked it. It seemed to work just fine during the different relay wiring scenarios. I was able to get low and medium speeds out of it. I took it to get charged today, but they have not been able to figure it out either.

He did ask me if there were 2 different A/C harnesses available, and I told him there was one with the anti-diesel relay and one without.

Are replacement resistors available for these vehicles?

Could the fact that I have the harness for the system with the anti-diesel relay hooked to a system that doesn't have it be causing the problem, or does that matter?

thanks

jhow66 · 09-20-2006, 10:11 PM

Yes you can buy resistors. After studying the diagram there should be no differance in either harness as you have nothing pluged into it. Try this:
1--Ignition switch on-fan switch on low- there should be power out of fan switch on yellow only.
2--with above still in the same position go to relay and check for power on dark blue wire-if so fan should run slowly-if no power on dark blue wire the resistor is bad.
3--same as #1 with fan on medium-power out on yellow and light blue both-check as in #2
4--same as #1 with fan on high-power out on yellow,light blue and small orange-if you have it this way, fan switch is ok.
(either your resistor is bad or not plugged up if the above checks out.

kna4977 · 09-21-2006, 07:40 PM

Quote:

Originally Posted by jhow66

Yes you can buy resistors. After studying the diagram there should be no differance in either harness as you have nothing pluged into it. Try this:
1--Ignition switch on-fan switch on low- there should be power out of fan switch on yellow only.
2--with above still in the same position go to relay and check for power on dark blue wire-if so fan should run slowly-if no power on dark blue wire the resistor is bad.
3--same as #1 with fan on medium-power out on yellow and light blue both-check as in #2
4--same as #1 with fan on high-power out on yellow,light blue and small orange-if you have it this way, fan switch is ok.
(either your resistor is bad or not plugged up if the above checks out.

I went by the place that is recharging the A/C and troubleshooting the wiring today to bring them the old harness so that they could compare that harness to the harness I have that has the anti-diesel relay. So far they are stumped as well and kept saying that everything appears to be wired correctly, and they bought another relay, that didn't fix the problem, and that there was voltage where there shouldn't be.

Huck · 09-21-2006, 08:46 PM

Using the OHM on your meter with power off---see if your ground from the relay is good to the body. I know you mounted it correctly etc. butttt check that gound using a meter. Just humor me on this~~. I can't tell you how many times I've see A/C trucks with only high speed due to a loose or poor ground at that relay!!

BLACK AND BLUE 67-72 · 09-21-2006, 10:13 PM

check your resistor, and the ground on your blower motor.

kna4977 · 09-29-2006, 07:41 PM

After a lot of time, money, and hardwork, I finally have the system working correctly. Turns out the wiring harness itself was wired wrong. I had the fan working correctly, off, low, med and high, until today. I had the fan set at low, and all the sudden low went to medium eventhough it was still set at low. medium is medium and high is high. off is off. any ideas??

67chevy2wd · 09-29-2006, 08:15 PM

Now that sounds like a switch problem, like on of the resistors shorted in the low setting and now low and medium have the same amout of resistance in the circuits. If it was me I would swap in a different control, that is if you have one lying around.

kna4977 · 09-29-2006, 08:59 PM

The control is new. Do you think it might be the resistor?

67chevy2wd · 09-29-2006, 09:06 PM

I am not very familiar with the contols as I have not played with them, Where are the resistors located in the circuit. I would guess a resistor problem but I am not alway right. If you had it working correctly and you didn't play with it again and this problem happened then I would say there is a good chance that is what it is.

kna4977 · 09-29-2006, 09:48 PM

Quote:

Originally Posted by 67chevy2wd

I am not very familiar with the contols as I have not played with them, Where are the resistors located in the circuit. I would guess a resistor problem but I am not alway right. If you had it working correctly and you didn't play with it again and this problem happened then I would say there is a good chance that is what it is.

There is a wiring diagram posted earlier in this thread that will show you where it is within the system

jhow66 · 09-29-2006, 09:52 PM

Resistor.

kna4977 · 10-02-2006, 08:02 PM

I am still having some problems. First, the air doesn't blow as cold as I think it should. The compressor runs all the time when the control is set for A/C, not sure if it is supposed to or not. The POA valve and hoses are frosty/icy with the system engaged with a lot of condensation due to engine heat when the system is turned off. The center outlet has colder air than the side vents. The water valve seems to always let water through, except on the rare occasion that I can increase vacuum to it by placing the truck in park and ideling at about 2000 rpm. In drive, under load, it has virtually no vacuum until I let off and coast which allows the air to be somewhat cooler, but not cool enough. The lack of vacuum at the water valve I believe is most likely causing heat to mix with the cool air, but like I said before as vacuum increases, the air does get colder, but still not as cold as it should be. Also, is there a way to increase vacuum on a consistent basis so that there is always enough to close the water valve? I did try to bypass the water valve to see if it the A/C was colder that way, but the truck wants to overheat. Any tips you can give me would be great!

09-19-2006, 10:02 PM	#52
mrein3 Registered User Join Date: Feb 2000 Location: Center City, MN, USA Posts: 3,253	Re: Help! How can I get my heater fan to stop running???? Check the voltage before and after the resistor block with the fan on medium and low. You may have fried those resistors. __________________ '70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN

09-19-2006, 10:21 PM	#53
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	Re: Help! How can I get my heater fan to stop running???? Did you check the resistor when you were installing the AC-was it plugged up? Sounds like what Mrein' says. __________________ 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 Last edited by jhow66; 09-19-2006 at 10:22 PM.

09-20-2006, 10:11 PM	#55
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	Re: Help! How can I get my heater fan to stop running???? Yes you can buy resistors. After studying the diagram there should be no differance in either harness as you have nothing pluged into it. Try this: 1--Ignition switch on-fan switch on low- there should be power out of fan switch on yellow only. 2--with above still in the same position go to relay and check for power on dark blue wire-if so fan should run slowly-if no power on dark blue wire the resistor is bad. 3--same as #1 with fan on medium-power out on yellow and light blue both-check as in #2 4--same as #1 with fan on high-power out on yellow,light blue and small orange-if you have it this way, fan switch is ok. (either your resistor is bad or not plugged up if the above checks out. __________________ 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

09-21-2006, 08:46 PM	#57
Huck Senior Member Join Date: Jun 2001 Location: Shelbyville, KY Posts: 3,269	Re: Help! How can I get my heater fan to stop running???? Using the OHM on your meter with power off---see if your ground from the relay is good to the body. I know you mounted it correctly etc. butttt check that gound using a meter. Just humor me on this~~. I can't tell you how many times I've see A/C trucks with only high speed due to a loose or poor ground at that relay!!

09-21-2006, 10:13 PM	#58
BLACK AND BLUE 67-72 Firefighter Join Date: Feb 2001 Location: Yellville, Ar, USA Posts: 1,943	Re: Help! How can I get my heater fan to stop running???? check your resistor, and the ground on your blower motor. __________________ '72 Chevy SWB 350 Auto '67 GMC LWB 350 4 speed '70 Chevy 4x4 Stepside 350 Auto Yellville, Ar. USA

09-29-2006, 07:41 PM	#59
kna4977 Senior Member Join Date: Jul 2006 Location: Midlothian TX Posts: 306	Re: Help! How can I get my heater fan to stop running???? After a lot of time, money, and hardwork, I finally have the system working correctly. Turns out the wiring harness itself was wired wrong. I had the fan working correctly, off, low, med and high, until today. I had the fan set at low, and all the sudden low went to medium eventhough it was still set at low. medium is medium and high is high. off is off. any ideas??

09-29-2006, 08:15 PM	#60
67chevy2wd Registered User Join Date: Sep 2003 Location: New Salem, ND Posts: 1,558	Re: Help! How can I get my heater fan to stop running???? Now that sounds like a switch problem, like on of the resistors shorted in the low setting and now low and medium have the same amout of resistance in the circuits. If it was me I would swap in a different control, that is if you have one lying around. __________________ 07 Chevy classic LBZ Duramax (a few mods) '67 Chevy 1/2 ton 2wd (in pieces) '69 Chevy 1/2 ton 2wd (on hold) '71 GMC 3/4 ton 4x4 ‘71 GMC 1/2 ton 2wd suburban

09-29-2006, 08:59 PM	#61
kna4977 Senior Member Join Date: Jul 2006 Location: Midlothian TX Posts: 306	Re: Help! How can I get my heater fan to stop running???? The control is new. Do you think it might be the resistor?

09-29-2006, 09:06 PM	#62
67chevy2wd Registered User Join Date: Sep 2003 Location: New Salem, ND Posts: 1,558	Re: Help! How can I get my heater fan to stop running???? I am not very familiar with the contols as I have not played with them, Where are the resistors located in the circuit. I would guess a resistor problem but I am not alway right. If you had it working correctly and you didn't play with it again and this problem happened then I would say there is a good chance that is what it is. __________________ 07 Chevy classic LBZ Duramax (a few mods) '67 Chevy 1/2 ton 2wd (in pieces) '69 Chevy 1/2 ton 2wd (on hold) '71 GMC 3/4 ton 4x4 ‘71 GMC 1/2 ton 2wd suburban

09-29-2006, 09:52 PM	#64
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	Re: Help! How can I get my heater fan to stop running???? Resistor. __________________ 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

10-02-2006, 08:02 PM	#65
kna4977 Senior Member Join Date: Jul 2006 Location: Midlothian TX Posts: 306	Re: Help! How can I get my heater fan to stop running???? I am still having some problems. First, the air doesn't blow as cold as I think it should. The compressor runs all the time when the control is set for A/C, not sure if it is supposed to or not. The POA valve and hoses are frosty/icy with the system engaged with a lot of condensation due to engine heat when the system is turned off. The center outlet has colder air than the side vents. The water valve seems to always let water through, except on the rare occasion that I can increase vacuum to it by placing the truck in park and ideling at about 2000 rpm. In drive, under load, it has virtually no vacuum until I let off and coast which allows the air to be somewhat cooler, but not cool enough. The lack of vacuum at the water valve I believe is most likely causing heat to mix with the cool air, but like I said before as vacuum increases, the air does get colder, but still not as cold as it should be. Also, is there a way to increase vacuum on a consistent basis so that there is always enough to close the water valve? I did try to bypass the water valve to see if it the A/C was colder that way, but the truck wants to overheat. Any tips you can give me would be great!



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