Fan Blower Speed - only High Works
 

On my 1982, only the High setting on the fan blower works.

So far I have replaced the blower switch, AC High Blower Motor Cutout Relay and the AC Blower Motor Resistor and none of these have fixed the problem.

(I turned the key to Accessories - does the car have to be running to properly test these parts?)

Any ideas?

Thanks!

I would check the voltages at the resistors.
http://www.europeancorvette.com/phot...77/Page016.jpg

Fan Blower Speed - only High Works
 

I have already replaced the Resistor - all 3 are in one unit. What should the voltages or resistance be?

Check ground(black wire)to blower.........sometimes the wire heats and breaks somewhere along it's length.
Try grounding blower with another source ,if it cures your problem, your ground is bad.

Good Luck

i would check for voltage at c137 , drk. blue wire coming out of resistors. since its the common supply to the motor from the resistors. should be able to check it at the high speed blower relay. may be a bad connector or wire. since the low, med, med hi dont work.
believe the key should be turned forward to the on position for fan to work

You are aware that the high speed uses a different feed circuit and fuse than the lower speeds?

Fan Blower Speed - only High Works
 

What fuse is the lower speed fuse?

I just went through all of this. Replaced bad motor. Long story. The fuse is in the fuse box under drivers dash. Depending which year. I have 78 and top right I believe is heat and ac. 25 amp fuse. The high speed works seperate from the fuse/

:iagree:
You've thrown all the parts you can throw at it,its time to get your test light out and actually diagnose the problem.

Also I found my duct on passenger side kicked in toward firewall and loose. Aparently it was hanging my fan up. Not allowing it to run only but high speed. When I pit the duct in place the fan worked fine. Lot of varables

Fan Blower Speed - only High Works
 

78 C3 Light Corvette Blue:

So you are saying it was the fuse (among other things)?

No the fuse was good. I had a hard time finding the right size blower wheel for 1. 2nd the Blower duct under the glove box on passenger side was pushe loose into the fire wall. It was keeping the fan from turning. The lower speeds don't put out much voltage. That's why the guys were asking and trying to help in that direction. But check the fuse and duct under dash (glove box). Make sure it is tight to the vent there. Not up against the wheel. If the duct is resting on or blocking the wheel it won't turm axcept on high. Hope you find it. I did the same thing. Replaced relay and blower resistor.

have you replaced/checked the function switch it powers the low speed switch, they are kind of junk especialy the aftermarket ones

Don't know if this will help you but I did a simplified version of that schematic.

1st.. I would verify the fuse is good.... then i would verify the fuse is making good contact in the fuse panel. Make sure the terminals are not corroded and that the fuse is making good contact.

2nd I'd put the blower motor in a lower speed.. then I would check the purple wire for power... If the purple wire has power then verify the motor ground.

If the purple wire is without power... then go to the dark blue wire and see if you have power.. The inputs to the resistor are Tan, Light Blue and Brown... so when you put the blower switch in the dash in one of the lower speeds it changes which wire gets the power.. the power then runs through the resistor and comes out on the blue wire. Knowing this.. I'd test for power on each of the three wires.. depending on what speed you set the blower switch in the dash on.

This system always seems to confuse people but it's actually a pretty basic system.

As with any electrical problem you'll need the right tools.... A cheap test light and a multimeter will be your best friend.

http://willcoxcorvette.com/images/he...078-82%202.JPG 18243

:thumbs:
Willcox

Fan Blower Speed - only High Works
 

Great info - Thanks all. I will have to get the right tools and do some testing.

Certainly not trying to hijack this thread but would like to know if I can use this schematic for my 70 coupe with AC. Is it the same?
Thanks GG

Nope.. sorry I took a few days off.

I have one for your car about ready to roll.

Give me a few days and I'll post it on the site.

Willcox

Ok.. here it is.. I worked on it last night and this morning..

1970 Heater and AC wire and vacuum hose schematic.

http://willcoxcorvette.com/images/19...ematic%202.jpg 18243

Thank you Mr Ernie,
Thanks for taking time to draw up & post the 70 schematic.
Well appreciated I can assure you. :cheers:
GG.

Your Welcome Greg-

This is an easy one since it's pretty much a colored version of the AIM one.. You'll find the original in C60 toward the end of that section. Only difference is the AIM version has a wiring mistake on it! Yep.. the wires did not change colors from one end to the other as the original shows..

Thank you again Greg.. really enjoy doing this stuff.. I trying to finish up the Power Steering Control Valve Video.. that one will be nice.. But I had to start over on it and we have been hammered with Shop work so that kills me from getting a helper.. :D

E