When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
My father had a couple of 77's that did this.....apparently the fan always runs.....
Vette Vues magazine had a tech tip a million years ago to cut the brown wire at the fan motor. This was the low speed fan wire. Cut it and it no longer spins.....Dad did this to both of them and it worked.
You will have to verify on a 79' if it is the same color....
It was the brown on my 79. Just unplug it. No need to cut it like a 77. Its located on back pass side. right on top when you open hood. It shares a plug with 3 or 4 other wires. Just unplug the brown one.
Good pict here. Its the brown wire at bottom of picture
As the title says, my 1979 c3 blows hot air out of the footwell vents constantly. Turning the air off or turning it to "cool" does nothing. Thoughts?
'79s have a constant ventilation fan that always runs at low speed.
If you can't move the location of air delivery you have a vacuum failure.
If you can move the location of air delivery but it is always heated, you have a problem in the heat cut-off system. See this thread Pay particular attention to the type of cut-off switch in your car. If like mine, the switch was fine but the "extension condom" wore out.
But how do i fix the problem? Now i cant blow any air at all.
Sounds to me like you have a vacuum failure. Can you change mode? e.g. from floor to defrost?
Without vacuum the system will run only at low fan speed from the floor. It will also be heated air because there is no vacuum to close the hot water shut-off valve when the temperature lever is all the way to "cold".
Sounds to me like you have a vacuum failure. Can you change mode? e.g. from floor to defrost?
Without vacuum the system will run only at low fan speed from the floor. It will also be heated air because there is no vacuum to close the hot water shut-off valve when the temperature lever is all the way to "cold".
Lack of vacuum like what 'SwampeastMike' mentioned is CORRECT...because the vents go into default mode which makes the air blow out at the floor boards if NO vacuum is present....or leaking badly enough.
Sounds to me like you have a vacuum failure. Can you change mode? e.g. from floor to defrost?
Without vacuum the system will run only at low fan speed from the floor. It will also be heated air because there is no vacuum to close the hot water shut-off valve when the temperature lever is all the way to "cold".
Can't change mode or fan speed. No matter what setting I have it on, it blows hot air at my feet (or did till I unplugged the brown wire).
I'll look into the vacuum issue this week when I have some more free time, thanks!
Can't change mode or fan speed. No matter what setting I have it on, it blows hot air at my feet (or did till I unplugged the brown wire).
I'll look into the vacuum issue this week when I have some more free time, thanks!
There is ...or SHOULD BE a very small black hose that connects to a special 'T' vacuum fitting that gets vacuum supply from the vacuum hose for your headlight system going THROUGH the firewall over by the master cylinder.
The special "T" vacuum fitting that DUB mentioned is at the yellow arrow. The little vacuum line that feeds the HVAC system has the green arrow.
Ok I just went outside and checked and I DO have that fitting and it appears to be intact. The smaller vaccuum line (the one with the green arrow) runs over to the passenger side and in to the firewall.
If you have a hand vacuum pump connect it to that little vacuum line that feeds the HVAC system. It should pump down quickly and hold vacuum indefinitely. In the likely event that it won't hold vacuum at all, the next part of the chain is the HVAC mode selector switch. Be forewarned that replacement switches seem to suffer from the "China junk syndrome" even when "modified to seal and work properly" by vendors Disassembly, cleaning and some silicon grease were all I needed to get my original switch working perfectly.
If you don't have a hand vacuum pump, get one as you're going to need it
If you have a hand vacuum pump connect it to that little vacuum line that feeds the HVAC system. It should pump down quickly and hold vacuum indefinitely. In the likely event that it won't hold vacuum at all, the next part of the chain is the HVAC mode selector switch. Be forewarned that replacement switches seem to suffer from the "China junk syndrome" even when "modified to seal and work properly" by vendors Disassembly, cleaning and some silicon grease were all I needed to get my original switch working perfectly.
If you don't have a hand vacuum pump, get one as you're going to need it
Ok I finally got around to purchasing a hand vacuum pump. As you guessed, that little line holds zero vacuum.
Where can I find one of these HVAC Mode Selector switches? Are they universal(can I buy it at an auto parts store) or do I need one specific to my car?
Ok I finally got around to purchasing a hand vacuum pump. As you guessed, that little line holds zero vacuum.
Where can I find one of these HVAC Mode Selector switches? Are they universal(can I buy it at an auto parts store) or do I need one specific to my car?
Thanks
The vendors sell them. Willcox has one they call, "Modified to seal and work properly" but the one they sent me leaked worse than my original! Before you order a new one, I'd remove the old and see what has happened. It's easy to disassemble and all it seems to need to stop leaks is some silicon grease (look with plumbing supplies).
The problem is quite possibly but not certainly the switch. The main vacuum leading to it (the one you tested) may have a hole.
I forgot to mention this before but you need to check that little vacuum hose with the HVAC selector at the "Off" position. If it does not hold vacuum at that position the switch and the tube are the only possible problems as the switch is supposed to be complete sealed (i.e. not feeding vacuum to anything) in the "off" position. Those little vacuum lines are better described as a "pipe" as they are a very durable plastic instead of rubber. That's why you find some sort of rubberized connector at each end of them and also why mechanical damage or extreme heat are about the only things that will damage them.
Make certain that the hood seal (at the rear end of the hood) is in place and actually seals. Old seals get hard and shrink so that they do not seal well. When this happens, engine compartment heat flows out and into the cowl area where the passenger compartment air inlet vent is located. Always has been a big source of unwanted cockpit heat.
The vendors sell them. Willcox has one they call, "Modified to seal and work properly" but the one they sent me leaked worse than my original! Before you order a new one, I'd remove the old and see what has happened. It's easy to disassemble and all it seems to need to stop leaks is some silicon grease (look with plumbing supplies).
The problem is quite possibly but not certainly the switch. The main vacuum leading to it (the one you tested) may have a hole.
I forgot to mention this before but you need to check that little vacuum hose with the HVAC selector at the "Off" position. If it does not hold vacuum at that position the switch and the tube are the only possible problems as the switch is supposed to be complete sealed (i.e. not feeding vacuum to anything) in the "off" position. Those little vacuum lines are better described as a "pipe" as they are a very durable plastic instead of rubber. That's why you find some sort of rubberized connector at each end of them and also why mechanical damage or extreme heat are about the only things that will damage them.
Do you happen to have a picture of the HVAC switch so I know what I'm looking for? Google turns up ALOT of different images when I try to find it.
Thanks for all the help! I should have some time this afternoon to diagnosis it a bit more. I'll report back with what I find.
Please DO NOT take any of your hoses and fittings for granted as far as vacuum integrity. Your fittings are damn near 40 years old and I found on mine that the connectors were weak and the plastic hoses were brittle and had hairline cracks in them.
Although a PITA, you will need to trace your vacuum from the engine source, through the fire wall into the car. Take your glove compartment out and you will see a bunch of the hoses, tee fittings and connectors.
Use your hand held vacuum and undo and isolate each component for integrity. Most likely it is not your control valve on the console.
As I mentioned earlier, I swapped most of my old hoses for new and the system sprang back to life. My main issue was the little clear plastic connector on the engine and the plastic hose.
Last edited by billschroeder5842; 05-01-2016 at 01:18 PM.
04-24-2016, 02:13 PM
1979 footwell vents blow hot air constantly
Disassembly, cleaning and some silicon grease were all I needed to get my original switch working perfectly.
