Blower Motor Question

[76sierraclassic]

I was just wondering if someone can tell me if it's normal for the fan blower motor to run on high all the time when MAX A/C is on, regardless of what the fan speed switch is set to.

Thanks in advance...

Mike

[apstguy]

No it is not normal. You should have independent control of the fan.

[76sierraclassic]

That's what I thought, but it works like it should on any setting other than MAX A/C. But regardless of where the fan speed switch is set, when I change it to MAX, the fan goes on high.

Anyone have any suggestions on what to look at?

Thanks,
Mike

[Jonboy]

check the resistor on the heater box, beside teh blower motor. There should be 4 wires going to it, I believe. It's either that, or the fan switch itself, on the A/C control panel.

[plumbcut]

dont listen to these guys. Max AC = full speed fan, no matter what the speed switch is set to.

pc

[76sierraclassic]

Originally Posted by plumbcut

dont listen to these guys. Max AC = full speed fan, no matter what the speed switch is set to.

pc

Thanks for the info.

[N2TRUX]

Originally Posted by plumbcut

dont listen to these guys. Max AC = full speed fan, no matter what the speed switch is set to.pc

And so nicely stated too.

Ok I have one for ya. My fan only runs one speed no matter what. It doesn't seem to be high or low. It doesn't matter if it's on Max or not. I'm thinking a/c control. What's your opinion?

[plumbcut]

what year is the truck? right off the bat Im thinking blower motor resistor.. but give more info


pc

[N2TRUX]

Well I was wrong. I guess it helps if you can hear, and I can't. I normally keep my a/c on Max so that's why it was only one speed. I didn't think the fan was blowing high speed though. I turned the a/c to normal and all the fan speeds work.

I guess I need to compare the blower motor to a later truck and see if they are faster. I'm used to my late model trucks that will blow your hat off your head....

[Grim Reaper]

Originally Posted by plumbcut

dont listen to these guys. Max AC = full speed fan, no matter what the speed switch is set to.

pc

My 75, my 79, and my 88 do not do that. Still have full control over speed. MAX A/C is the same as regular A/C except it is in recirculate mode. Withthe cappy 134 it's always set on max except when my wife over comes my nasty start and smokes in the truck. Then I roll down her window and put it on regular A/C so it draws from the outside and doesn't circulate the smoke into the blower box.

[76sierraclassic]

Originally Posted by Grim Reaper

My 75, my 79, and my 88 do not do that. Still have full control over speed. MAX A/C is the same as regular A/C except it is in recirculate mode. Withthe cappy 134 it's always set on max except when my wife over comes my nasty start and smokes in the truck. Then I roll down her window and put it on regular A/C so it draws from the outside and doesn't circulate the smoke into the blower box.

OK...so now I'm confused. There are several folks saying that mine is functioning right, and others saying that their's function differently. How do we find out who's right? Was it some funky option, or do a bunch of us just have the same problem with our A/C blower or switch? If it's a problem that all of us have, then can anyone tell us what to do to fix it?

Mike

[Grim Reaper]

I didn't drive any of my trucks but I know on my 88 Burb with Dual air it does not work like that. It sounds like it's in Jet engine mode when the flap closes but still can control the fan speed.
HIGH is controled by that relay under the hood on the blower box. Actually it's all controlled there but the High setting is on a different circuit then the rest.
Wishe these were like my Toy with a A/C button and seperate inside out side control. I really hate that GM control. I can't make it work the way I want. I want Def blowing without A/C in the winter.

[NeCrOmAnCeR]

My 74 blows only on high when put into max AC, move it to normal and I get full control of fan speed. I agree with grim reaper, high is through the relay, the other three speeds go through the resistor block.

[Greenlee]

My 76' does the same thing, on max you cannot control the fan speed. I had an 81, 83, 85, and 88, and I don't remember them operating that way, although its been along time since I owned those trucks.

[Grim Reaper]

Hmmm All my trucks were K5's or Subs. I wonder if the SUVs are wired different then the trucks.

I'll double check the burb tonight when I get home and report back.

[plumbcut]

every AC truck Ive ever driven from 73-87 (there have been quite a few) have worked this way stock. If you goto the dealer to get a replacement switch, its an updated design (vs. the mid 70's anyway) and you have to change a little bit of wiring slightly.. its a no brainer (the installation/mod) but after the mod- it works to where max AC is not always on HIGH.... So if the switch has ever been replaced, it will work like you say. But if the system is the same as what rolled off the assembly line, max AC will be high fan only.

Dont think any of the blazer/burbs ive driven had a working AC so I never tried.. I have a 91 burb, Ill check it out next time I drive it.. Im 95% sure that max AC =high fan only in the '91...

pc

[N2TRUX]

All I want to know is do the later blower motors push more air? If I can get more air flowing from a later blower motor I'm all for it.

If not, what would you guys say is the better compressor? Is the early still long compressor beest, or is the later radial style better? It's freaking hot here and I need more cold air somehow.....

[plumbcut]

later style, definately and they use noticeably less power from the the engine, to run. Not to mention they look better... if I ever get around to doing my AC system right in my old truck, Im going to have an electric fan in front of the ac condensor, pushing air thru when the AC is on.. airflow across the condensor is KEY in keeping the air temp low. Also our systems were designed for R12 and thats what works best Id use propane before I chose 134a as a longterm setup.

as for the blower motor, im not sure.. id be interested in your findings though.. the older style works pretty good if all the vacuum doors and stuff are working and seal..

pc

[Greenlee]

I recently replaced just about my entire A/C system. I'm still using the old style long compressor, which I believe is the A6. The radial is called A4. I may have them backwards, but I think that is right. I asked around alot before doing the job and the one piece of advice I got over and over again was to buy a new compressor rather than a rebuild. The rebuilds can be found for less than $100 and a new one is about $400. I bought a new compressor and it is making noise anyway, so I am a little pissed. I was also told to buy A/C Delco, but I got conflicting reports regarding whether or not A/C Delco still makes the A6. I don't think mine is made by A/C Delco although it was represented as A/C Delco when I ordered it.

With respect to freon, I used something called "Freeze 12" which is supposed to be sort of a blend between 12 and 134a. At least that is how it was explained to me. I was told that it is colder than 134a. It seems to blow pretty cold to me, but I haven't had a truck with 134a to compare it with.

[NeCrOmAnCeR]

I personally have a Sanden compressor on my truck. I put it on when I converted my truck to R134 in 1995. Works like a champ, although the A/C on the truck didn't work before then so I cannot compare its performance verses a stock unit. But it is alot smaller.

[N2TRUX]

Originally Posted by plumbcut

......as for the blower motor, im not sure.. id be interested in your findings though.. the older style works pretty good if all the vacuum doors and stuff are working and seal..pc

Yeah that's the first thing I need to do is reseal all my ducts and vacuum doors. Every time I mess around under the dash I find another chunk of foam insulation has fallen out.

I figure I will seal everything up then so how it blows. If it isn't any better I want to try a later model fan to see if it has a faster speed.....

[SanitysBane]

i would never use 134A, heres y, R12 is chemical inert, meaning it doesn't react with anything at all. 134A is flamable, and it just a mixture of 2 gases, so if you have a leak the heaver gas will leak out and the lighter one will stay behind. also 134A will automatically cause you to lose 10% of your cooling capacity. freeze 12 acts just like freon 12 except its a mixture of gases as well. but you also don't loose your 10% capaticaty like 134A.