68 GTO A/C Heater electrical problem - Pontiac GTO Forum
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post #1 of 5 (permalink) Old 07-27-2013, 11:34 PM Thread Starter
 
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68 GTO A/C Heater electrical problem

The power to my A/C and heater control has gone away. I have power at the fuse block but none at the control switch. No A/C or heater blower at all. I traced the brown wire from the fuse block to what I think is called the A/C Master Relay which is mounted on the passenger side of the firewall in the engine compartment. The line coming in from the fuse block has power but no power comes out. Thinking it was a bad relay, I installed a new one but still nothing. I tested the relay on the work bench and could not get it to open so I sent it back and got a new one. Still no power comes out. so I am thinking that the relay must need to be triggered by something else. I'm pretty sure my A/C system is full and even if it was not, wouldn't the heater blower still come on? I have the original shop manual but there is no wiring diagram of the heating/ A/C system so I can't tell where to trace this down. I suspect this is a simple fix if I only knew where to look. Anyone have experience with this? Thanks in advance.
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post #2 of 5 (permalink) Old 07-28-2013, 12:48 AM
 
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Usually there is a resistor at the switch itself that sometimes goes bad. Does your clutch kick in at the compressor when you turn it to a/c? Check the connection where it plugs directly into the fan motor for corrosion, etc, wiggle it around... You did say you had power right up to the relay, yes? Go through all the basic things first. These can get kind of tricky, but with the schematics, you should be able to track it down. Someone here should have links to the diagrams.
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post #3 of 5 (permalink) Old 07-28-2013, 09:21 AM Thread Starter
 
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A/C problem

Thanks for the suggestions...I will check the resistor and fan connections. The compressor clutch does not engage. A heater wiring diagram would e great as I cannot tell where everything goes. Anyone have that? Thanks again...mark
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post #4 of 5 (permalink) Old 07-28-2013, 12:20 PM
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Do you have an in-line fuse holder in a wire coming off your alternator? My 69 did, and I know it supplies at least part of the power for the heat-A/C system. I'm not near my wiring diagrams right now..

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post #5 of 5 (permalink) Old 07-28-2013, 10:40 PM Thread Starter
 
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Inline fuse

Thanks Bear...I was thinking that there might be another fuse somewhere in the wiring system...I will have to unwrap some of the wiring to/from the alternator to check it out...another good lead...anyone have an A?C wiring diagram? I think I will also post my query in the tech forum...thanks again...Mark
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