78 Climate Control Fan / Blower
Thread Starter
Instructor
Joined: Feb 2008
Posts: 139
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From: Katy Texas
78 Climate Control Fan / Blower
Hi from Hot Texas!
I had my 78 out for a little run over the weekend and it was 105 degrees outside. My A/C System (which I had recently replaced) was keeping me comfortable - not icey cold like my C6 but Still cool. Well low and behold - the fan just shut off.... I was still 30 Miles from home. I was not happy... especially since I had just rebuilt the entire system... including the A/C Control Unit in the Cockpit.
My question is this - what is the best way to test which component is causing the issue without buying the Relay, Resistor, Blower Motor, A/C Control Unit, etc... I did have a spare relay but it did not do the trick so I don't think that's it. My Compressor does come on when i turn on the A/C but the fan won't blow.... Is there a way I can test whether it's the fan switch on the A/C Control? Or the Resistor under the Hood? Or the Blower Motor itself? I can tell that replacing the blower motor will not be fun since i have to remove the Coolant expansion bottle and what a pain that is.
Any advice as always is greatly appreciated
Cheers ~ Joe
I had my 78 out for a little run over the weekend and it was 105 degrees outside. My A/C System (which I had recently replaced) was keeping me comfortable - not icey cold like my C6 but Still cool. Well low and behold - the fan just shut off.... I was still 30 Miles from home. I was not happy... especially since I had just rebuilt the entire system... including the A/C Control Unit in the Cockpit.
My question is this - what is the best way to test which component is causing the issue without buying the Relay, Resistor, Blower Motor, A/C Control Unit, etc... I did have a spare relay but it did not do the trick so I don't think that's it. My Compressor does come on when i turn on the A/C but the fan won't blow.... Is there a way I can test whether it's the fan switch on the A/C Control? Or the Resistor under the Hood? Or the Blower Motor itself? I can tell that replacing the blower motor will not be fun since i have to remove the Coolant expansion bottle and what a pain that is.
Any advice as always is greatly appreciated
Cheers ~ Joe
Thread Starter
Instructor
Joined: Feb 2008
Posts: 139
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From: Katy Texas
Perfect - I'll take a look when I get home.
Besides the parts I listed originally: Relay, Fan Switch on A/C Control Unit, Resistor, Blower Motor.... are there any other failed components that could cause this behavior? I might add that i do hear clicking in the relay when I move the switch... but that's all.
Thanks again.
Joe
Besides the parts I listed originally: Relay, Fan Switch on A/C Control Unit, Resistor, Blower Motor.... are there any other failed components that could cause this behavior? I might add that i do hear clicking in the relay when I move the switch... but that's all.
Thanks again.
Joe
Thread Starter
Instructor
Joined: Feb 2008
Posts: 139
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From: Katy Texas
It was working on all speeds... No strange sounds coming from blower motor prior - or ever... It just shut off as if the switch was flipped... without any warning.
Hmmm I wasn't aware of the other fuse. I'd like to check that. I did check the one located in the fuse box. Where would the other be located?
Thanks a bunch
Hmmm I wasn't aware of the other fuse. I'd like to check that. I did check the one located in the fuse box. Where would the other be located?
Thanks a bunch
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
My 77 info. shows High fuse near power brakes under hood. Our A/C wiring is probably same or very similar.
The only problem I have had was a power wire from the speed switch at underhood connector near pass. rear of ig. shield near firewall. A wire was melted internally at the connector.
The only problem I have had was a power wire from the speed switch at underhood connector near pass. rear of ig. shield near firewall. A wire was melted internally at the connector.
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Thread Starter
Instructor
Joined: Feb 2008
Posts: 139
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From: Katy Texas
Okay - so this is a little embarrassing but it does have a happy ending. (But I have to claim innocence as I did not know this system prior to this thread )
Last night when I came home from work - I opened the hood of my 78 and Located the Blower Motor. My intention was to run a jumper to it to see if it worked. I wanted to either confirm or eliminate as the issue... Well guess what i found
The power wire had vibrated off and was just dangling there. I smiled such a big smile because I knew that i could now avoid hours of troubleshooting and replacing parts. Started her up and put A/C on Max with fan on High and she blew like a hurricane.
Thanks for all the great tips.
But I did discover a new Problem and I do need advice. When Re-attaching the Power Wire to the Blower Motor - I noticed a small white vacuum line just hanging there... It comes from the firewall near the distributor but I don't know where to attach it on the Engine compartment side... It was run and just hanging down near the blower motor and evaporator. It was pulling a vacuum so I just closed it with a small finishing nail and am now trying to figure out where it goes... Any ideas?
Thanks as always!!
Joe
)Last night when I came home from work - I opened the hood of my 78 and Located the Blower Motor. My intention was to run a jumper to it to see if it worked. I wanted to either confirm or eliminate as the issue... Well guess what i found
The power wire had vibrated off and was just dangling there. I smiled such a big smile because I knew that i could now avoid hours of troubleshooting and replacing parts. Started her up and put A/C on Max with fan on High and she blew like a hurricane.
Thanks for all the great tips.
But I did discover a new Problem and I do need advice. When Re-attaching the Power Wire to the Blower Motor - I noticed a small white vacuum line just hanging there... It comes from the firewall near the distributor but I don't know where to attach it on the Engine compartment side... It was run and just hanging down near the blower motor and evaporator. It was pulling a vacuum so I just closed it with a small finishing nail and am now trying to figure out where it goes... Any ideas?
Thanks as always!!
Joe
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
...
But I did discover a new Problem and I do need advice. When Re-attaching the Power Wire to the Blower Motor - I noticed a small white vacuum line just hanging there... It comes from the firewall near the distributor but I don't know where to attach it on the Engine compartment side... It was run and just hanging down near the blower motor and evaporator. It was pulling a vacuum so I just closed it with a small finishing nail and am now trying to figure out where it goes... Any ideas?
Thanks as always!!
Joe
But I did discover a new Problem and I do need advice. When Re-attaching the Power Wire to the Blower Motor - I noticed a small white vacuum line just hanging there... It comes from the firewall near the distributor but I don't know where to attach it on the Engine compartment side... It was run and just hanging down near the blower motor and evaporator. It was pulling a vacuum so I just closed it with a small finishing nail and am now trying to figure out where it goes... Any ideas?
Thanks as always!!
Joe
Thread Starter
Instructor
Joined: Feb 2008
Posts: 139
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From: Katy Texas
Guys - thanks so much.
Where is the Heater Shutoff Valve Located? Not sure what you mean by manual shutoff.
I can check this when I get home tonight. I love easy fixes
It is a stiff Vacuum line - white - and it is a very small diameter. I had to stick my tongue on it to even detect the vacuum on such a small hole; but the vacuum is there.
Where is the Heater Shutoff Valve Located? Not sure what you mean by manual shutoff.
I can check this when I get home tonight. I love easy fixes
It is a stiff Vacuum line - white - and it is a very small diameter. I had to stick my tongue on it to even detect the vacuum on such a small hole; but the vacuum is there.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Okay - so this is a little embarrassing but it does have a happy ending. (But I have to claim innocence as I did not know this system prior to this thread )
Last night when I came home from work - I opened the hood of my 78 and Located the Blower Motor. My intention was to run a jumper to it to see if it worked. I wanted to either confirm or eliminate as the issue... Well guess what i found
The power wire had vibrated off and was just dangling there. I smiled such a big smile because I knew that i could now avoid hours of troubleshooting and replacing parts. Started her up and put A/C on Max with fan on High and she blew like a hurricane.
Thanks for all the great tips. ...
Joe
)Last night when I came home from work - I opened the hood of my 78 and Located the Blower Motor. My intention was to run a jumper to it to see if it worked. I wanted to either confirm or eliminate as the issue... Well guess what i found
The power wire had vibrated off and was just dangling there. I smiled such a big smile because I knew that i could now avoid hours of troubleshooting and replacing parts. Started her up and put A/C on Max with fan on High and she blew like a hurricane.
Thanks for all the great tips. ...
Joe
Now you know something about the system. Since there are 2 power sources & no speeds, it was sounding like a bad connection at the blower or bad blower except I would expect the blower to make noise a while before failing.
PS Power also bypasses the switch & runs Low.
I changed Low to Off a long time ago.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
It should go to the heater shut off valve in the heater hose. Block off if no valve.
Easy to see on pass. side if there. Some have put a manual valve in if the vacuum heater shut off valve was missing.
Thread Starter
Instructor
Joined: Feb 2008
Posts: 139
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From: Katy Texas
This exercise was actually quite good for me and my 78 Vette. Not only did I correct my blower issue - I also corrected a long time problem that I had no idea there was a fix for; The excessive Heat in the Cockpit.
I read several related posts after your help and determined that instead of reconnecting the disconnected vacuum line to the stock heater shutoff valve - I could install a manual shutoff and relieve some of the heat in my cockpit.... Man what a difference!!! A quick trip to the auto-parts store and around 20 bucks, and 1 hour of my time - allowed me to install two proper heater manual shutoff valves, replace my aging hoses, and remove the old valve that wasn't working.... Man my car is so much cooler now... I can't believe I have been living with this needlessly for two years
Now my A/C Keeps me nice and cool!
Here are a couple of photos of what I pulled out and What I put in. you guys are the best!
Cheers ~ Joe
I read several related posts after your help and determined that instead of reconnecting the disconnected vacuum line to the stock heater shutoff valve - I could install a manual shutoff and relieve some of the heat in my cockpit.... Man what a difference!!! A quick trip to the auto-parts store and around 20 bucks, and 1 hour of my time - allowed me to install two proper heater manual shutoff valves, replace my aging hoses, and remove the old valve that wasn't working.... Man my car is so much cooler now... I can't believe I have been living with this needlessly for two years
Now my A/C Keeps me nice and cool!
Here are a couple of photos of what I pulled out and What I put in. you guys are the best!
Cheers ~ Joe
Last edited by joes86vette; Aug 23, 2011 at 11:49 PM.
