D.E Posted July 4, 2022 Share Posted July 4, 2022 Has anyone had this problem.This is the 2nd one that has done thjs.But this time it caught on fire had to put out flame under dash pad.Melted the upper a/c vent.I've owned this car since new and the 1st time it just melted the plug and the wires a little but this time it really caught fire.Also I need the wiring diagram of the color wires to the switch itself.Thanks for help Quote Link to comment Share on other sites More sharing options...
jft69z Posted July 4, 2022 Share Posted July 4, 2022 Something could be drawing excess current to be catching fire like that (compressor clutch or blower motor), dirty contacts/connections on the switches & old wires with high resistance could possibly cause heat (smoke) too. Check to make sure proper sized fuses are installed as well. Here are a couple of pics of the factory manual regarding HVAC. Disregard some of the highlights, they were from a problem someone else had. Quote Link to comment Share on other sites More sharing options...
MC1of80 Posted July 5, 2022 Share Posted July 5, 2022 71 a/c wiring is different from the 70 and the 72 is also different from the 70 and 71. The 71 has relays under the passenger side dash that is unique to 71 only. I believe one controls the clutch on the compressor. When it fails the clutch stays on. I have this issue with "Barn Find" purchased the parts but haven't had the chance to install them yet. Quote Link to comment Share on other sites More sharing options...
D.E Posted July 5, 2022 Author Share Posted July 5, 2022 Thanks I will look at it when i get the switch.The brown wire from the master is also melted ,Got the upper vent from Summit but they didn't have a switch.Ordered it from OPGI. Quote Link to comment Share on other sites More sharing options...
D.E Posted July 10, 2022 Author Share Posted July 10, 2022 My new switch will be here Tuesday sometime. So I'll work on it when it gets here.Have to check the vacumn hose they got a little hot. 1 Quote Link to comment Share on other sites More sharing options...
D.E Posted July 25, 2022 Author Share Posted July 25, 2022 where is the resistor that goes to the blower motor and to the fan switch.Got the switch last week will start to replace burned wires this week.Thanks for help Quote Link to comment Share on other sites More sharing options...
jft69z Posted July 25, 2022 Share Posted July 25, 2022 It's on the evaporator box, under the hood. Location circled in red. Quote Link to comment Share on other sites More sharing options...
D.E Posted July 25, 2022 Author Share Posted July 25, 2022 Thanks I heard that could be a problem with overheating of switch.Will check it out Quote Link to comment Share on other sites More sharing options...
D.E Posted July 25, 2022 Author Share Posted July 25, 2022 The brown wire on master switch it goes to the fuse panel,correct.It has a connector it plugs into behind the speedometer hsg.The one on mine is melted and that nis the only wire I don't know where it goes.Thanks foe help.Can you get the resistor for the a/c box?Got the switch wired and back in also the other wires that were melted that were above the radio going to the pass side of dash.Thank you again for help. Quote Link to comment Share on other sites More sharing options...
1970mcss Posted July 26, 2022 Share Posted July 26, 2022 I'm thinking the brown wire is for the tachometer, I hope someone can confirm. Good luck Quote Link to comment Share on other sites More sharing options...
jft69z Posted July 26, 2022 Share Posted July 26, 2022 The brown wire is the power feed from the fuse panel, underlined in yellow on the schematic. Dennis may confirm, as we had this discussion specifically about that brown wire at the time, when I sent that marked up print to him. Quote Link to comment Share on other sites More sharing options...
Dtret Posted July 26, 2022 Share Posted July 26, 2022 That is correct. But my problem ended up being a voltage regulator problem. It was creating full power to that wire causing the blower to run 24/7. Quote Link to comment Share on other sites More sharing options...
D.E Posted July 26, 2022 Author Share Posted July 26, 2022 Thanks I will hope to get it finished today maybe.I had converted to 1 wire so no voltage regulator.But will check the relay and the blower motor.Got to splice some of the vacuum lines on dash controls Quote Link to comment Share on other sites More sharing options...
D.E Posted August 7, 2022 Author Share Posted August 7, 2022 Got the wiring finished and vacuum line finished today but the master switch amd the brown wire unit still gets warm after a little while running the fan with engine off.Just had the blower motor running and wires to switch were warm.Not going to put dash pad back on till I solve this problem.Does anyone have their dash pad off to test the switch and wires getting warm.Thanks for help Quote Link to comment Share on other sites More sharing options...
jft69z Posted August 7, 2022 Share Posted August 7, 2022 You might want to hook a meter up and see how much current it's drawing. Would be a little more accurate & easier to compare with others than 'wire temperature'. Quote Link to comment Share on other sites More sharing options...
D.E Posted August 7, 2022 Author Share Posted August 7, 2022 Went back out and I can't get a high speed on fan fuse is not blown at relay.Got the other 2 resistors to replace the ones on the car.Not good with meters what draw is it suppose to be.Thanks Joe for help.If this keeps up I will change to a Vintage Air unit.Hate to not keep it factory since I've bought it new in 71.And it will freeze you out Quote Link to comment Share on other sites More sharing options...
D.E Posted August 15, 2022 Author Share Posted August 15, 2022 Replaced resistor and the wires going to the master switch is still getting hot to touch with the fan on.Could the fan motor bee the problem. Still no high speed fan.Going to replace relay and fan motor .I think that is everything that has to do with the fan control. Quote Link to comment Share on other sites More sharing options...
D.E Posted August 28, 2022 Author Share Posted August 28, 2022 Today replaced the resistor with a brand new one.Also replaced the blower motor with a new one.The Master switch tan and green wires still get warm to touch.Ran the car with a/c on for 10 minutes or so and the wires were warm to touch.Fan speed switch was not warm.The high speed relay has noe came in yet so no high speed fan.But 12 volts going to relay.Hate to keep asking about this but i don't want another fire under dash.The master switch has a set of points sanded the a liittle also today. Quote Link to comment Share on other sites More sharing options...
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