C3 Blower

[John H.]

I have 72 base 350 4-speed with AC. When I turn the blower switch to a higher
speed it hardly increases. Each higher setting does increase air speed however
air speed FEELS only marginal. Also when switch is moved to highest setting
the air flow drops to hardly nothing.
What fix's do you recommend. This low air flow has been like this for many years. Just last year a/c duct work was totally replaced but it still blows
weak.... Big John

[Jim T.]

Re: C3 Blower

John the high speed function of the blower switch has its own fuse. This is a inline fuse locted in the engine compartment. This fuse on my 70 is located between the master cylinder and power relay mounted on the fenderwell. If this fuse is blown the high speed will not work although all the other speeds work.

[Lee S.]

Re: C3 Blower

There are a whole lot of issues here. Most are covered at the site referenced below.

Bob Chadwick is moderator of the C3 Forum at Corvette Action Center. I contributed my experiences on the blower fan so he may share it across the hobby. While I know this aspect of my car is not judging compliant, I feel a whole lot better about it riding around in cool AC treated air.




C3 Corvette Heating, Ventilation, & AC

[Harmon C.]

Re: C3 Blower

John The first few speeds are weak so they are probably OK. The highest speed has it's own fuse and it the is in line type. It is located on the drivers side fenderwell on a red wire that is hooked to the horn relay area. This was a seperate wire for A/C cars only and is used at the highest speed only. It can be high or low on the fenderwell and may be under the brake booster. I will bet you find it to be your problem as it is far removed from the blower area. Lyle

[Patrick H.]

Re: C3 Blower

If my memory serves correctly, the high speed blower relay, mounted on the heat exchanger box on the passenger's side, also controls high speed fan function. I have restored high speed to my 71 (back in 1994 or so) by replacing this relay when I found the fuse was A-OK.

You may find that you can take apart the relay and test and clean it to make it work, too. I was able to so that on my Cutlass.

Patrick

[John H.]

Re: C3 Blower

Make sure the terminals on the ground wire for the heater blower are clean and shiny at both ends (at the blower connection and at the starter attaching bolt); that ground also serves the wiper motor and the A/C blower relay.

[Jeffrey S.]

Re: C3 Blower

John:
Patrick is correct- the high speed fan relay could very well be the culprit. Check the plastic terminals to see if any are burned off. On my '69 they have a habit of melting since they are so close to the exhaust manifold. Over the years I have replace a half a dozen or so. Hope this helps.
Jeff

[John H.]

Re: C3 Blower

Guys, thanks for all your comments. I have been away from my computer and car
for several days, however I will try all these good suggestions.
This NCRS discussion site is very, very helpful.
I plan on getting car rejudged at Waco Regional in November.
A little additional information about my heater blower bug-a-booh: my
relay terminals were melted due to exhaust heat, relay wiring connector was replaced a few months ago.
I am in the process in checking out the relay itself, I'll respond with a update. The in line fuse was also replaced a few months ago. Still low air flow.

I might add that this blower relay/horn relay wire WAS PINCHED about a year
ago while in a repair shop, for a heater core replacement. The attaching nut
that holds the heater box assembly,was tightened down onto this wire.
The bolt/nut goes thru the firewall. Bolt attaches to heater bracket and
TEMP.CONTROL CABLE. This cable housing was completely melted to the bare wire.
Everywhere that cable laid against wires and insulation was burned.
Car's interior caught on fire. Most of duct asemblies were all melted.
Shop refused any wrong doing. Said radio shorted out. Radio fuse is fine.
Radio plays fine. My insurance settled. I am going to court October 19th, for
law suit regarding deminished value and smoke damage etc...Will keep you posted.

[Tony Roussos]

Re: C3 Blower

Hello. My 1971 had no Hi blower operation. The connector was melted by heat, but wires were not shorted. The relay was bad. Once replaced, the Blower HI worked properly. Make sure wires are correct per diagrams found in assembly manual or Hayes/Chilton style manuals. Test terminals with an Ohmmeter.

Tony

[John H.]

Re: C3 Blower

Tony thanks for your comments.
How do you test the relay, removal etc. Thanks Big John.

[Tony Roussos]

Re: C3 Blower

Hi John,

To test the relay, I pulled back the case tabs, found the coil pins and checked for continuity (0 ohms.) If no continuity, then the coil/relay is bad. If continuity is present, I then applied 12Vdc to the coil pins and looked to see if the poles connected. Then, I checked for continuy on the poles when energized. The pole contacts may need to be burnished or sanded with a smooth emry cloth if oxidized.

I hope this helps.

Tony

[John H.]

Re: C3 Blower

Tony, thanks for the info. Big John