long post A/C-horn issues
Thread Starter
Intermediate
Joined: Aug 2008
Posts: 36
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From: Long Island NY
long post A/C-horn issues
Hello everybody, i own a 72 coupe. here's my problem. last week i replaced the A/C belt, a/c blew nice and cold. ( R-12 system) a few days later the a/c didnt work.the toggle switch works in the console. when i roll the wheel down from off to max a/c the compressor does spin.but the clutch doesen't engage. i pulled the plug off the compressor and cleaned it up.i cleaned up the a/c relay plug too.i figured it might be the relay or the thermal switch that took a dump. that same day my horns weren't working either. 
when i hit the horn i hear the relay on the drivers side click.so i after disconnecting the horn wires i took a hot lead, tested them and they both work fine.i checked all of the fuses in the panel, none were blown. here's my question: is the horn relay supposed to click or is it bad.or is the the A/C hi blower relay thats bad. or could the thermal limiter be blown. i need help on this one. regards, George
when i hit the horn i hear the relay on the drivers side click.so i after disconnecting the horn wires i took a hot lead, tested them and they both work fine.i checked all of the fuses in the panel, none were blown. here's my question: is the horn relay supposed to click or is it bad.or is the the A/C hi blower relay thats bad. or could the thermal limiter be blown. i need help on this one. regards, George
7th Gear
Joined: Jun 2009
Posts: 7
Likes: 0
From: Tupelo Mississippi
The wire that powers the a/c compressor may have come off (just a guess). if not, put 12V to it and see if it energizes (momentarily). It'slocated behind the pulley on a single connector. The a/c clutch should magnetize when the climate control is turned to normal or max settings. This makes the pulley pick up the compressor motor and start it turning. There must be freon in the system in order to complete the circuit, otherwise power will not reach the compressor.
The fan relay should "click", however, that does not necessarily mean that the pionts inside the relay are making a good connection. I took the cover off my relay and was able to polish my points w/ emory cloth and it now works fine. All of this said, the relay is only for the "max" fan setting. The other speeds are controlled through the resistors that are located on the evaporator housing. they work independently. If the relay is bad, you should still have the other speeds working. The purple wire comming out of the fan relay that powers the fan motor will have 12V when on max. The other 3 speeds that work from the resistors will have approximately 9V,6V, and 3V respectively when on the lower settings.
I had a long winded troubleshooting reply to the other horn problem a couple of days ago. He has 2 threads goung about the same things. Go back a couple of days and look for it.
The fan relay should "click", however, that does not necessarily mean that the pionts inside the relay are making a good connection. I took the cover off my relay and was able to polish my points w/ emory cloth and it now works fine. All of this said, the relay is only for the "max" fan setting. The other speeds are controlled through the resistors that are located on the evaporator housing. they work independently. If the relay is bad, you should still have the other speeds working. The purple wire comming out of the fan relay that powers the fan motor will have 12V when on max. The other 3 speeds that work from the resistors will have approximately 9V,6V, and 3V respectively when on the lower settings.
I had a long winded troubleshooting reply to the other horn problem a couple of days ago. He has 2 threads goung about the same things. Go back a couple of days and look for it.
7th Gear
Joined: Jun 2009
Posts: 7
Likes: 0
From: Tupelo Mississippi
I found it. Hope this helps.
My horn button rocks towards the outer edges. The horn relay is a plastic three prong relay (my old one was yellow, new one is black) hanging in front of the fuse buss under the drivers side dash. There are 3 wires going to it (using my 1981 as my example). The black wire is a ground, the red wire is hot, the green wire is the power wire that feeds the horns. When you push the horn button you will complete the circuit for the relay. This will in turn magnetize the relay and "make" the points in the relay. Therefore, allowing voltage to travel through the green wire to the horns.
In order to check the system, remove the relay and connect a volt meter or test light to the black (-) and red (+) wires through the connector. If you have voltage when the button is pushed the horn mechanism is working properly. Next you need to check the relay. You can re install the relay and see if there is voltage on the green wire when the button is pushed. I took my relay apart and found it was rusted beyond repair (about $12.00 or so) and installed a new one. Problem solved. You may want to bench test it since it is such a tight fit under the dash. Look to see which connector corresponds to each wire. Connect 12 volts to the red wire terminal, ground the black wire terminal and use your meter/test light to ensure 12 volts on the green wire terminal. You should hear the relay click as the coil magnet is energized. If all this is working properly, you will need to test each horn by putting 12 volts directly into the horn itself. The problem is most likely the relay, unless you have have been working on the steering column. If there is a problem between the relay and the horn units there will be a grounding issue on the horn units or a broken green wire supplying the horns. This should allow you to at least narrow your search to a specific part failure.
Hope this helps, If you need more clarification let me know.
jay
My horn button rocks towards the outer edges. The horn relay is a plastic three prong relay (my old one was yellow, new one is black) hanging in front of the fuse buss under the drivers side dash. There are 3 wires going to it (using my 1981 as my example). The black wire is a ground, the red wire is hot, the green wire is the power wire that feeds the horns. When you push the horn button you will complete the circuit for the relay. This will in turn magnetize the relay and "make" the points in the relay. Therefore, allowing voltage to travel through the green wire to the horns.
In order to check the system, remove the relay and connect a volt meter or test light to the black (-) and red (+) wires through the connector. If you have voltage when the button is pushed the horn mechanism is working properly. Next you need to check the relay. You can re install the relay and see if there is voltage on the green wire when the button is pushed. I took my relay apart and found it was rusted beyond repair (about $12.00 or so) and installed a new one. Problem solved. You may want to bench test it since it is such a tight fit under the dash. Look to see which connector corresponds to each wire. Connect 12 volts to the red wire terminal, ground the black wire terminal and use your meter/test light to ensure 12 volts on the green wire terminal. You should hear the relay click as the coil magnet is energized. If all this is working properly, you will need to test each horn by putting 12 volts directly into the horn itself. The problem is most likely the relay, unless you have have been working on the steering column. If there is a problem between the relay and the horn units there will be a grounding issue on the horn units or a broken green wire supplying the horns. This should allow you to at least narrow your search to a specific part failure.
Hope this helps, If you need more clarification let me know.
jay
