heater fan - always on?

[byproxy]

heater on my 73 works great. have both high and low speeds and heat and defrost.

problem is that the fan always runs. the "off" position doesn't actually turn the fan all the way off.

i'm assuming this isn't normal? presumably i'd need a new switch? just checking before i dig into the control unit. the guy i bought it from said it's always been that way and was assuming the fan just stayed on all the time in these trucks.

 

[HotRodPC]

IIRC, this will be an AC model truck right? It's more than likley the blower relay box under the hood on the AC Evaporator box not far from the fan motor. The Relay contacts are probably stuck and won't release. Sometimes using a screwdriver, tap on the little metal box and you'll hear the blower shut off.

Or, you can disconnect the battery for a minute. That shuts it's off, then you reconnect the battery and it stays off. Give that a try first. That is the most common reason for this problem.

You must be registered for see images attach

 

[Driver4r]

My 76 non-AC truck's fan is always on. Its an air circulation feature. Pretty sure the roundeyes always run, just mabey really slowly.

 

[HotRodPC]

My 76 non-AC truck's fan is always on. Its an air circulation feature. Pretty sure the roundeyes always run, just mabey really slowly.

And I have heard of something similar too and maybe that's the heat only units, or the older model?

Also, some think cuz the fan switch is all the way down, that it's off. That IS NOT the off position for the fan. That is LOW. Off is the top slide switch all the way to the left where it says OFF. That also is the OFF position for the fan.

If his is doing what mine did, it's not running slow. It was running on high with the key off and me out of the truck. If I'm understanding that's what he's talking about.

 

[HotRodPC]

My 76 non-AC truck's fan is always on. Its an air circulation feature. Pretty sure the roundeyes always run, just mabey really slowly.

And now that you mention this, and I go back and reread what he's got here, I jumped to conclusions, and yep, it's probably normal. My bad !!! But for anyone who has a fan stay on high after you've shut the key off and get out, your problem is the relay I've made a photo of.

I'll be tagging this thread for future users.

 

[Driver4r]

And now that you mention this, and I go back and reread what he's got here, I jumped to conclusions, and yep, it's probably normal. My bad !!! But for anyone who has a fan stay on high after you've shut the key off and get out, your problem is the relay I've made a photo of.

I'll be tagging this thread for future users.

 

[HotRodPC]

Careful. Had a spammer really early this morning. I found the ban hammer, stretched the muscles a bit and warmed it up already today.

 

[1low4x4]

Easy fix for that is to push the upper tab down then plug the connector back in. This keeps the damn the damn blower from running all the time and burning up. Still works when you want it to and only then.

You must be registered for see images attach

You must be registered for see images attach

 

[Driver4r]

Careful. Had a spammer really early this morning. I found the ban hammer, stretched the muscles a bit and warmed it up already today.

We are all just here to have fun,

 

[HotRodPC]

Easy fix for that is to push the upper tab down then plug the connector back in. This keeps the damn the damn blower from running all the time and burning up. Still works when you want it to and only then.

You must be registered for see images attach

You must be registered for see images attach

Now this here is the fan resistor for High Med Low. Not the relay. The relay is a small Tin covered rectangular box.

That part there is what's gone bad if all you have is Fan on High Speed and no low and/or medium speeds.

 

[bucket]

I don't mind the low speed fan...

 

[Stroked]

Easy fix for that is to push the upper tab down then plug the connector back in. This keeps the damn the damn blower from running all the time and burning up. Still works when you want it to and only then.

You must be registered for see images attach

You must be registered for see images attach

Wait, so what are we bypassing here?

 

[1low4x4]

Basically turning the constant blower off. That way it lasts longer and you dont have unwanted air coming out of yo ur vents until you turn it on

 

[Stroked]

Ohh, ok. I guess I never noticed mine doing that.

My dang fan has Low and Medium, but no High.

 

[MrMarty51]

The early years of the square body had the blower running to "Pressurize" the cabin to keep unwanted dust from leaqking in like it does with the pre 73 models.
I remember a guy I worked for many many years ago bought a brand spanking new 73 GMC and He complained about that and the dealer did a tech check and that is what was passed down.
SO,if You want unwanted dust settling into Your nice Chevy/GMC square bodies then shut offt the blower completely.
After I found out about this I now roll up all the windows and run the blower on high when traveling dirt roads.thats all.