A/C high speed blower relay bypass? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Aarons72s · 11-29-2006, 01:25 PM

Has anyone ever bypassed the high speed blower motor relay? I am sick of blowing them every 12 months. ANd only having low and medium speed. Why did gm even use this anyway? The heat trucks dont use one and from what I can tell they use the same blower motor, except the a/c one has a larger case and a hole for a vent tube. So why shouldnt it be hooked up like the heat blower? If someone has done this could you please describe what you did. And if no one has I will try it myself and post the results. Thanks again.

mrein3 · 11-29-2006, 01:38 PM

I converted my truck from non-AC to AC.
They factory relay was on the behind the glove box stuff box I bought but I still rigged up my own. Here is what I did.

I took the wire from the fan switch that is hot when you want high-speed. I made this a control wire to a bosch style relay. Right from the positive junction block on the RF fender I ran a 10 or 12 gauge wire to the relay. I put a 20 amp fuse in this wire, under the hood, on top of the RF inner fender for easy access. Then from the hot when energized prong on the relay I ran 10 or 12 gauge wire to the fan.

I use the same relay for hi beams, low beams, hi-speed fan, and driving lights. I keep a spare in the glove box. I had one fail a while ago but that was because my truck was parked outside that winter and water was dripping on the relay around the hood. I moved the relay to a dry location and no longer have a problem. (That was a headlight relay. The fan relay is screwed on to the heater ducts).

Aarons72s · 11-29-2006, 01:45 PM

Cool thanks mrein3. Yah the stock relay leaves much to be desired. I might try that. Try to see what my options are. Before wasting time and money on another one of those stock relays. Thanks again.

neonlarry · 11-29-2006, 03:15 PM

I would run some kind of relay, the stock switch can barely handle the slower speeds.

jacobs · 11-29-2006, 07:36 PM

Don't bypass the relay. Years ago, I installed an AC fan from the junkyard after my old fan motor quit. Shortly afterward my heater switch burned out due to the increased load. I then installed a relay and a new heater switch and it's worked great ever since.

mrein3 · 11-29-2006, 08:28 PM

Quote:

Originally Posted by jacobs

Don't bypass the relay. Years ago, I installed an AC fan from the junkyard after my old fan motor quit. Shortly afterward my heater switch burned out due to the increased load. I then installed a relay and a new heater switch and it's worked great ever since.

What I did is replace the factory relay with a newer style one.
If you try to run the fan on high with just current through the switch and not a relay you'll burn it up for sure.

One thing I noticed when I was collecting parts is that the fan switch on the heater control I bought and EVERY switch in the junk yard I looked at showed some signs of melting. I bought a new switch, a new connector, and used factory style contacts in the connector. I'm pretty sure my system will outlast factory wiring.

Aarons72s · 11-29-2006, 08:34 PM

Ok so how about another option, run a heater blower motor? they will bolt right up, I got a a/c blower on an heater box. How about that as an option?

Edit, i have seen alot of melting when those motors start going out, when they start going out they start eating some serious voltage.

11-29-2006, 01:25 PM	#1
Aarons72s Registered User Join Date: Apr 2006 Location: oklahoma Posts: 10,669	A/C high speed blower relay bypass? Has anyone ever bypassed the high speed blower motor relay? I am sick of blowing them every 12 months. ANd only having low and medium speed. Why did gm even use this anyway? The heat trucks dont use one and from what I can tell they use the same blower motor, except the a/c one has a larger case and a hole for a vent tube. So why shouldnt it be hooked up like the heat blower? If someone has done this could you please describe what you did. And if no one has I will try it myself and post the results. Thanks again.

11-29-2006, 01:38 PM	#2
mrein3 Registered User Join Date: Feb 2000 Location: Center City, MN, USA Posts: 3,254	Re: A/C high speed blower relay bypass? I converted my truck from non-AC to AC. They factory relay was on the behind the glove box stuff box I bought but I still rigged up my own. Here is what I did. I took the wire from the fan switch that is hot when you want high-speed. I made this a control wire to a bosch style relay. Right from the positive junction block on the RF fender I ran a 10 or 12 gauge wire to the relay. I put a 20 amp fuse in this wire, under the hood, on top of the RF inner fender for easy access. Then from the hot when energized prong on the relay I ran 10 or 12 gauge wire to the fan. I use the same relay for hi beams, low beams, hi-speed fan, and driving lights. I keep a spare in the glove box. I had one fail a while ago but that was because my truck was parked outside that winter and water was dripping on the relay around the hood. I moved the relay to a dry location and no longer have a problem. (That was a headlight relay. The fan relay is screwed on to the heater ducts). __________________ '70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN

11-29-2006, 01:45 PM	#3
Aarons72s Registered User Join Date: Apr 2006 Location: oklahoma Posts: 10,669	Re: A/C high speed blower relay bypass? Cool thanks mrein3. Yah the stock relay leaves much to be desired. I might try that. Try to see what my options are. Before wasting time and money on another one of those stock relays. Thanks again.

11-29-2006, 03:15 PM	#4
neonlarry Registered User Join Date: Feb 2002 Location: Vacaville, CA Posts: 2,745	Re: A/C high speed blower relay bypass? I would run some kind of relay, the stock switch can barely handle the slower speeds. __________________ 70 C/10 Light Red 350/TH350, HEI, Duals w/40 series Flows, 91 seat, LED taillights 99 Pontiac S/C GTP, SLP Ram Air hood, GMPP Konis & springs 95 Neon ACR, MP PCM, AFX UDP, 3.0 CAI

11-29-2006, 07:36 PM	#5
jacobs Registered User Join Date: Sep 2005 Location: 9000' Mountain Man Posts: 326	Re: A/C high speed blower relay bypass? Don't bypass the relay. Years ago, I installed an AC fan from the junkyard after my old fan motor quit. Shortly afterward my heater switch burned out due to the increased load. I then installed a relay and a new heater switch and it's worked great ever since.

11-29-2006, 08:34 PM	#7
Aarons72s Registered User Join Date: Apr 2006 Location: oklahoma Posts: 10,669	Re: A/C high speed blower relay bypass? Ok so how about another option, run a heater blower motor? they will bolt right up, I got a a/c blower on an heater box. How about that as an option? Edit, i have seen alot of melting when those motors start going out, when they start going out they start eating some serious voltage. Last edited by Aarons72s; 11-29-2006 at 08:36 PM.



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