Blower motor fan switch
Thread Starter
Intermediate
Joined: Feb 2006
Posts: 37
Likes: 0
Blower motor fan switch
Help! The blower motor fan switch on my 78SA only works on low and med
speed, when I move it into hi, it stays the same as med or doesn't operate
at all. I've tried to track this down using the various Corvette manuals I
have to no avail. I do have the defogger timer assm. disconnected since
there's a break in the defogger wires somewhere in the back window. I think
this might have something to do with it. But connecting the timer makes no
difference. Yes the A/C, heat, etc. works fine, just no hi speed out of the
blower motor. Anyone on the list have any experience on the subject?
A. Sclafani
speed, when I move it into hi, it stays the same as med or doesn't operate
at all. I've tried to track this down using the various Corvette manuals I
have to no avail. I do have the defogger timer assm. disconnected since
there's a break in the defogger wires somewhere in the back window. I think
this might have something to do with it. But connecting the timer makes no
difference. Yes the A/C, heat, etc. works fine, just no hi speed out of the
blower motor. Anyone on the list have any experience on the subject?
A. Sclafani
Thread Starter
Intermediate
Joined: Feb 2006
Posts: 37
Likes: 0
now I know when the defogger is activated there's current sent to the black wire on the hi speed fan relay. How can I completely disconnect the defogger so it doesn't interfere with the hi speed fan?
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
I can only speak for 1973 as I went through the same problem.
http://forums.corvetteforum.com/show...ighlight=relay
http://forums.corvetteforum.com/show...ighlight=relay
Instructor
Joined: May 2004
Posts: 209
Likes: 6
From: Glendale AZ
There is an inline fuse that operates the fan on high speed. Look for a single wire along the firewall towards the fan. I had the same problem with my 75. The wire was between the distributor and heater.
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Originally Posted by jd1a
There is an inline fuse that operates the fan on high speed. Look for a single wire along the firewall towards the fan. I had the same problem with my 75. The wire was between the distributor and heater.
On my 73 its on the drivers side near the brake booster and master cylynder
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
#1 check red wire at high speed blower relay for 12 volts
#2 if you have 12 volts at red wire then ground black wire and if that makes it run then its the rear window defog interfering
#3 if you have 12 volts at red wire with black grounded -check orange wire for 12 v and if you have it and blower is not on high- replace relay
#4if your car is late production it wont have rear defog bypass
Hope this helps
Oh I forgot if it is early and you have the defog switch disconnected the relay will not have a ground and wont run.
Oh and you ask about disconnecting the defog-just cut the black wire coming out of relay(the one next to the orange) and ground it-thats how late productions are wired-find the black ground wire for blower ground and connect the two-thats how the factory did it.
#2 if you have 12 volts at red wire then ground black wire and if that makes it run then its the rear window defog interfering
#3 if you have 12 volts at red wire with black grounded -check orange wire for 12 v and if you have it and blower is not on high- replace relay
#4if your car is late production it wont have rear defog bypass
Hope this helps
Oh I forgot if it is early and you have the defog switch disconnected the relay will not have a ground and wont run.
Oh and you ask about disconnecting the defog-just cut the black wire coming out of relay(the one next to the orange) and ground it-thats how late productions are wired-find the black ground wire for blower ground and connect the two-thats how the factory did it.
Last edited by ...Roger...; Aug 22, 2006 at 12:00 PM.
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Thread Starter
Intermediate
Joined: Feb 2006
Posts: 37
Likes: 0
Yes it's a 78 Silver Ann. I'll try those suggestions, thank you very much. Also I've located the wires that run down to the fan (the're hiddeen under the pass side fender behind the overflow res.) one is purple and I'm going to clean the connection (it plugs together), but there's no inline fuse.
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Originally Posted by dwncchs
His car is a 78 isnt it? Dont tell me I wrote that essay for nuttin !!!
When people dont fill out their profile sometimes its hard to figure out
Yes looking back... Now I see 78 SA
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Originally Posted by Bob Onit
I guess it was.
When people dont fill out their profile sometimes its hard to figure out
Yes looking back... Now I see 78 SA
When people dont fill out their profile sometimes its hard to figure out
Yes looking back... Now I see 78 SA
Race Director
Joined: Feb 2005
Posts: 16,100
Likes: 17
Originally Posted by dwncchs
Yes I agree it does make it a little easier to help if you have more info-but we "gotter done" anyway.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Originally Posted by rihwoods
Good info..my 78 SA (August vette) de-fog works...high speed rarely works.....changed relay..still nothing....dirt in switch ?