C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette

Full Voltage to Heater A/C Blower

 
Old 03-13-2019, 12:01 PM
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platinummaker
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Default Full Voltage to Heater A/C Blower

Hi Guys,
In a effort to improve the efficiency of my HVAC on the 72, I was hoping to ensure the highest voltage be obtained to the blower motor on the high fan setting. I have been scratching my head and was thinking of something similar to a relay providing direct fused voltage to the blower from the alternator, similar to the modifications to provide full voltage to the headlamps. For you soothsayers of Ohm's law could you please some help.
Thanks
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Old 03-13-2019, 01:20 PM
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kansas123
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Have you replaced your phan with one for a C4? Birdcage a bit deeper so requires installing a spacer but it will blow more air. I am also interested in the answer to your question. Let's see what happens....
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Old 03-13-2019, 01:43 PM
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Hammerhead Fred
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Originally Posted by platinummaker View Post
Hi Guys,
In a effort to improve the efficiency of my HVAC on the 72, I was hoping to ensure the highest voltage be obtained to the blower motor on the high fan setting. I have been scratching my head and was thinking of something similar to a relay providing direct fused voltage to the blower from the alternator, similar to the modifications to provide full voltage to the headlamps. For you soothsayers of Ohm's law could you please some help.
Thanks
On A/C cars that's already designed in. On High fan there is a separate circuit and fuse that provided voltage to the fan (this also protects the switch).
Usually the fan is not the issue. Usually there is a air blockage on the firewall side of the evaporator coil.
Search the forum and you'll find photos of bird nest, leaves, mice nest ect blocking the evaporator because there is no filter nor mesh between the air inlet at the passenger side of the windshield and the duct work.

Last edited by Hammerhead Fred; 03-13-2019 at 02:02 PM.
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Old 03-13-2019, 02:07 PM
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platinummaker
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Originally Posted by Hammerhead Fred View Post
On A/C cars that's already designed in. On High fan there is a separate circuit and fuse that provided voltage to the fan (this also protects the switch).
Usually the fan is not the issue. Usually there is a air blockage on the firewall side of the evaporator coil.
Search the forum and you'll find photos of bird nest, leaves, mice nest ect blocking the evaporator because there is no filter nor mesh between the air inlet at the passenger side of the windshield and the duct work.
Thanks Hammerhead. So do I assume the fused orange wire going to the blower is providing FULL alt/batt voltage?
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Old 03-13-2019, 02:39 PM
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7T1vette
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Correct. Other possible problems with "weak" fan performance are bad ground connection and burnt switch contacts. The latter issue could be resolved with your relay idea.

When new, the C3 cars blew LOTS of air into the cabin. That was never a problem. Age takes its toll....

Last edited by 7T1vette; 03-13-2019 at 02:41 PM.
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Old 03-13-2019, 08:49 PM
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'75
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Increasing the size of the ground wire to the blower motor will help too, I never understood why the original is so much smaller than the power wire.

Last edited by '75; 03-13-2019 at 08:50 PM.
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Old 03-13-2019, 11:10 PM
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7T1vette
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GM was "cheap" on some incidental stuff. They spent lots of money in development...which is why these cars are still running WELL.
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