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Topic: a/c heater wire smoked

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a/c heater wire smoked (1/16)
8/26/14 10:56pm

snake97
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Metairie, LA - USA

Vette(s):
1979 Black, Oyster interior purchased in March 1980

Joined: 7/7/2013
Posts: 24

Just converted a c to 134. I used classic auto air system, went in nicely. I now have a problem with burned wires. The fan was working on all speeds until I went to charge the system. At first only the high speed worked. On my way home I smelled something burning and then my blower quit. When I got home I saw The red wire, that I believe goes to a relay burned and the wire was broken from the heat. I replaced the wire, and it did ok for a few minutes. When I raised the rpm to about 2000 that wire burned and the power to the blower motor also burned. I replaced that wire and installed an inline fuse on the power to blower. It did fine until I raised the rpm. The 20 amp fuse blew and when I replaced it with a 30 amp, it blew when I just turned the a c on. I'm a bit green on electrical issues and was wondering if anyone had any ideas. Don't know if it could be relay or blower motor, or anything else as I had the whole heating and cooling system apart. thanks p.s. the worst thing I've ever done was when I changed the heater core. It didn't leak, but I changed it anyway since I was doing the a c. I was worried that as soon as I got the a c done it would then start leaking. My vocabulary got a lot more colorful.

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Re: a/c heater wire smoked (2/16)
8/27/14 12:36pm

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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
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We're gunna need a little more info on this one.
What all did you change, exactly? Did any o f it require modifying the wiring harness?
Do you have, or can you get some pics of the wiring that is melting? Is it buring under the dash, or out under the hood?

Something is obviously not right....I wouldn't keep tempting fate by just replacing the burnt wiring without finding and correcting the problem.

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Re: a/c heater wire smoked (3/16)
8/27/14 1:29pm

rraider1
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Woodland, WA - USA

Vette(s):
1977 T-Top,350,Auto Black Ruby Pearl,Steeroids R&P conversion

Joined: 10/14/2003
Posts: 1165

Where did you Install the fuse before the relay or after. The 79 basic diagram does not show the high speed relay for AC. but for a 1980 the Red or Org power wire should come from a fusible link at the starter to a splice point then to the relay. something is wrong that the fusible link did not protect the wires. to draw that much current it has to be a direct short to ground. It should be at the relay because in low,med relay deenergized you use the same circuit to the blower and would be protected by the 25 amp AC fuse.

Joel do you have a diagram that shoes the 79 AC circuit ?

Re: a/c heater wire smoked (4/16)
8/27/14 1:48pm

snake97
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Metairie, LA - USA

Vette(s):
1979 Black, Oyster interior purchased in March 1980

Joined: 7/7/2013
Posts: 24

thanks for the reply. I replaced everything from evap. core to condenser. The wires that burned are under the hood The first to burn was at a plug in the harness for the ac i think. It was red and went int the relay. The other was in the same plug. It has 2 black wires coming off of it, 1 going to the same relay that was not damaged, the other was a black wire going to the terminal on the engine side of the blower motor. That wire had the insulation melted off. I also read that the resistor that goes in the heater box controls the low speed for the blower. When I replaced the a c I had everything apart and it's possible that part may have been damaged. I tried to be careful, but sorry to say, I may get clumsy at times.I've never done ac before, but i"m trying to learn. Maybe in time I can be of some help to others. thanks

Re: a/c heater wire smoked (5/16)
8/27/14 1:52pm

snake97
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Metairie, LA - USA

Vette(s):
1979 Black, Oyster interior purchased in March 1980

Joined: 7/7/2013
Posts: 24

I installed it on the black wire under the hood that goes to the engine side of the blower motor. There was another wire in the plug that goes to the relay.

Re: a/c heater wire smoked (6/16)
8/27/14 2:32pm

rraider1
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Woodland, WA - USA

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1977 T-Top,350,Auto Black Ruby Pearl,Steeroids R&P conversion

Joined: 10/14/2003
Posts: 1165

I think the wires at your blower motor might be reversed. the 2 black wires that come from the same connector 1 goes to the blower relay the other would go to the ground clip of one of the mount bolts of the blower itself. the single wire from relay goes to the hot of the blower fan.

Re: a/c heater wire smoked (7/16)
8/27/14 3:09pm

snake97
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Metairie, LA - USA

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1979 Black, Oyster interior purchased in March 1980

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thanks for the help. I'll check what you suggest.

Re: a/c heater wire smoked (8/16)
8/27/14 5:00pm

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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

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rraider1 said: I think the wires at your blower motor might be reversed. the 2 black wires that come from the same connector 1 goes to the blower relay the other would go to the ground clip of one of the mount bolts of the blower itself. the single wire from relay goes to the hot of the blower fan.

Ed zachary what I was thinkin....direct short at the blower motor.
The resistor does control fan speed for low, low medium, and medium speeds. The high speed works directly from the relay. Thumbs Up

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Re: a/c heater wire smoked (9/16)
8/29/14 12:57pm

dwa175
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leesburg, FL - USA

Vette(s):
1979 coupe and now 2007 c-6

Joined: 7/19/2014
Posts: 195

maider just car back from restore shop, heater fan not working also no start,now where is the blower motor just read motor gets power for stater maybe same wiring is not right . heater blower fan only works on high I have no power I will keep looking and see how you make out dwa

Re: a/c heater wire smoked (10/16)
8/30/14 11:31am

dwa175
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leesburg, FL - USA

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1979 coupe and now 2007 c-6

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Posts: 195

guys where is the heater/ac fan motor

Re: a/c heater wire smoked (11/16)
8/30/14 12:20pm

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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

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Passenger side engine compartment, under the fender area on the firewall. To the passenger side of the A/C plenum/box. You'll have to remove the coolant reservoir to get to it.

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Re: a/c heater wire smoked (12/16)
8/30/14 1:05pm

rraider1
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Woodland, WA - USA

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1977 T-Top,350,Auto Black Ruby Pearl,Steeroids R&P conversion

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Posts: 1165

I think you need to really look at your wiring from the starter up. I would not replace the fusible link with a fuse. The fusible link will hold under high current loads for a brief period of time. depending on the fuse it will react almost instantaneous. so on high speed fan start up you might blow a fuse but not a fusible link.

I tried to find what amp rating the fusible links are but I'm not sure the info is 100 percent, the general info on fusible link are you just install on 4 Ga smaller than the wire you are protecting

I think the 79 has 2 at the starter Not sure they may be black which I think they are rated for 100+ amps for 15 sec with a continues rating of 40 amps.

The fuse might help find the short if you have one but something was not wired correctly in the beginning their must not have been any fusible links if the wires burned up.

Fusible links look just like regular wires, except the insulation is made out of a special, flame-proof material. The easiest way to test them is to tug on them. A blown link will stretch like a rubber band.

http://www.autoshop101.com/forms/hweb1.pdf

http://www.madelectrical.com/catalog/fusible-link.shtml

Re: a/c heater wire smoked (13/16)
9/2/14 1:29am

snake97
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Metairie, LA - USA

Vette(s):
1979 Black, Oyster interior purchased in March 1980

Joined: 7/7/2013
Posts: 24

Thanks for the help. After checking wires to make sure they weren't reversed, I discovered the problem. The tab where you plug the hot lead on was real loose. I replaced the motor and that seemed to take care of the problem. It's kind of hard to reverse the wires as the power has a rubber boot that should slip over a rubber grommet on the fan motor. when I pulled the old fan off to do my a c work, it worked fine. That's why I didn't replace it. After putting everything back together, I plugged in the power. It is in a spot under the fender, so you kind of have to feel for the lead to plug it in. After 35 years I guess the rubber insulation breaks down and disintegrates when you fool around with it. Plugging in the lead blindly seems to have done it in. Morale of the story is I should ha gone the extra couple and replaced the motor, since I replaced everything else.It would have been easier to replace the fan motor when everything was out in front of me, would have saved me from melting wire and the hours trying to figure the problem out, thee burnt up resistor in the heater box, and worst of all hearing from some people telling me about constantly sinking money into my car. I don't need to hear that. Like I tell people, I've owned that car longer than I've been married. It's got seniority. Once again thanks for the response from the forum.

Re: a/c heater wire smoked (14/16)
9/2/14 7:30am

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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

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Joel Adams
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My Link

(click for Texas-sized view!) NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Re: a/c heater wire smoked (15/16)
9/5/14 3:45pm

snake97
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Metairie, LA - USA

Vette(s):
1979 Black, Oyster interior purchased in March 1980

Joined: 7/7/2013
Posts: 24

Had same issues .Replaced Resistor on top of heaterbox gave me my 3 lower speeds on fan back. One of the spring coils got damaged.

Re: a/c heater wire smoked (16/16)
9/15/14 7:41pm

dwa175
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leesburg, FL - USA

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1979 coupe and now 2007 c-6

Joined: 7/19/2014
Posts: 195

thanks for help,but it took one young strong young man to pull call and it opened,cable is worn out new one is on the way,info you guys was good you can open hood with one push for screw driver its work but I would only try with tool,i could not get my hand under hood when closed but alls well thanks again dwa

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