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Topic: AC fan problem

in Forum: C3 Cooling and Heating Systems


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AC fan problem (1/20)
 7/9/06 8:22pm
warbird
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Roseland, NJ - USA

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I went over my AC yesterday, held 230 PSI for 20 min. System was cooling great, but my problem is my fan speed won't go into high speed. I have a new control switch, and AC/heater control panel. I had the motor & fan tested (just in case I had to replace them) and  everything worked great. Could my switch gone bad so quick ? Has anyone have any suggestion.

Without the high speed there isn't enough air blowing out to cool the cabin.    

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AC fan problem (2/20)
 7/9/06 8:31pm
cthulhuLifetime Member
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Hot Springs, AR - USA

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[QUOTE=warbird]

I went over my AC yesterday, held 230 PSI for 20 min. System was cooling great, but my problem is my fan speed won't go into high speed. I have a new control switch, and AC/heater control panel. I had the motor & fan tested (just in case I had to replace them) and  everything worked great. Could my switch gone bad so quick ? Has anyone have any suggestion.

Without the high speed there isn't enough air blowing out to cool the cabin.    

[/QUOTE]

did you check the wire itself for a break.  test it for continuity end to end.

also.. to help the cabin cooling..  have you put a shut off vavle on the heater core?



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AC fan problem (3/20)
 7/9/06 8:37pm
warbird
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Roseland, NJ - USA

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Yup, did all that. The fan doesn't change speeds no matter were I put the switch.
AC fan problem (4/20)
 7/9/06 9:09pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


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You probably need to replace the fan speed resistor. On the top of the A/C box.

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AC fan problem (5/20)
 7/9/06 11:34pm
warbird
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Roseland, NJ - USA

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Joel, the fan speed resistor was tested to see if it got current. However are you suggesting that even if it's receiving current it may still be defective ?
AC fan problem (6/20)
 7/10/06 12:07am
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Duncanville, TX - USA

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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


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It can be getting juice, but is it sending that juice out(back thru the switch)?
Also, you may need to test/check the high-speed relay. It is only used for the high speed of the fan, but could cause other problems, too.
Did you replace the fan speed switch recently, and do you still have the old one? If so, swap them and see if there is any change. That will tell you if the switch is the problem.
My switch(on the '74) doesn't work all the time. Sometimes I have to "jiggle" it to get it to switch speeds. I have a new one, but....I'm jest too darn lazy to change it! Adams' Apple38907.8811805556

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AC fan problem (7/20)
 7/10/06 10:04pm
warbird
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Roseland, NJ - USA

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Joel, I was in Reading PA today and Stopped at Stoudts Corvette and PU the relay and a new resistor. Hopefully, I'll get a chance this weekend to swap out the parts.

Thanks 

AC fan problem (8/20)
 7/11/06 3:35pm
annicorvetteLifetime Member
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BILOXI, MS - USA

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Do you have a rear defrost ? if you do check this--in my 78 the fan is wired so the high speed fan is disabled if the rear defrost is on. Don't ask why i just know it is.

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AC fan problem (9/20)
 7/12/06 11:01am
warbird
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Roseland, NJ - USA

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No defroster
AC fan problem (10/20)
 7/12/06 11:21am
gs77vet
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Hey Warbird, I had the same problem with my 77 vette, check your fuses, high speed runs off of a different fuse. Mine is a 25 amp. I installed a bus breaker, (part number CBF 25 at NAPA). My fuse is located in the fuse box at the very top, it's a mother to get to for me because I am 6'4" so I find a smaller person or a very limber person to get to it. good luck, Gene

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AC fan problem (11/20)
 7/12/06 11:27am
warbird
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Roseland, NJ - USA

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Thanks Gene, I'm not as tall as you but, my eating habits make it hard to reach certain places.
AC fan problem (12/20)
 7/22/06 10:54pm
kstyerLifetime Member
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CUYAHOGA FALLS, OH - USA

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Some of our cars have a hot lead directly from a fusiable link to the high position on the blower relay.  Some are fused or use a circit breaker.  If you have a high speed blower relay, the relay uses the switch to control the lower speeds through the resistor block, and uses a separate power supply to the relay to supply direct power through the relay to the blower motor for high speed.   In this case the high speed switch on the dash supplies power to trigger the relay when you select high blower.kstyer38920.8302430556
AC fan problem (13/20)
 8/22/06 4:56pm
2 cruznLifetime Member
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Poquoson, VA - USA

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[QUOTE=annicorvette]Do you have a rear defrost ? if you do check this--in my 78 the fan is wired so the high speed fan is disabled if the rear defrost is on. Don't ask why i just know it is.[/QUOTE]

Is it possible they use the same circuit and if both are on high the AMP draw would be too high?



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AC fan problem (14/20)
 8/22/06 8:05pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


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More than likely.

It should be noted tho, that on the '74(and earlier cars, up to '77), the rear defrogger was simply an extra blower fan that blew on the rear winder. The later cars('78-82) wid da large rear winder had imbedded defrogger circuits in the glass.
The 'lectric defroggers take quite a bit-o-'lectristity, which is why they are almost always on a timer. Adams' Apple38951.7151273148

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AC fan problem (15/20)
 9/1/06 5:22pm
LeeW78
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LAKE KATRINE, NY - USA

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I have just the reverse problem.  The high speed works but the lower setting do nothing.  Any suggestions?
AC fan problem (16/20)
 9/1/06 11:01pm
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That could be the blower switch, or the resistor bad. It could also simply be a fuse.
On most cars, the high speed blower is on a completely different circuit. This is why most of the time, it is the high speed that doesn't work, but the low speeds do. But, the other way happens also. I would start by checking fuses, and then the switch.

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AC fan problem (17/20)
 9/12/06 11:59am
gs77vet
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Hey Lee, AA is right, different fan speed, different fuse. Just one of the small things that makes owning one of these beauty's fun, Huh. Gene

AC fan problem (18/20)
 1/2/07 12:01am
warbird
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Roseland, NJ - USA

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It works !
I had the car out for a ride the other day, started to play around with the A/C Heater controllers and everything works Confused. I've gone crazy trying to figure this problem out, and low and behold, it's working Wits%20End.
Hey, at least it's working, now if it will work in the summer is another question.
AC fan problem (19/20)
 1/2/07 11:39pm
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Now...you know the first time you need that high speed blower with the A/C on, it ain't gonna work!!

Sounds like you may just have a bad connection somewhere, or one of the micro-switches in the control unit(thumbwheels). Hey, as long as it works, eh?

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AC fan problem (20/20)
 1/3/07 12:03am
warbird
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Roseland, NJ - USA

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I have no idea how it got fixed. Confused
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