MY AC WILL NOT TURN ON

  • Tiny
  • chrishurssey
  • 1978 Ford F-100
  • 54,000 miles

My ac will not turn on. I know it is not getting power because I had this problem before. I took it to the shop and I know they replace my module under the hood for engine problems it was fixed but im not sure what was done to get the ac fixed. And I would like to fix the problem myself. I checked all the fuses they all work I would also like to see a diagram of the ac wiring system. Please help and thank you.

Wednesday, February 6th, 2013 AT 6:28 AM

6 Answers

  • Tiny
  • hmac300
  • Expert
  • 41,621 posts

Have it checked for pressure normally when it wont' run it's low on pressure and this si a R12 system so suggest switching to R134. You probably have a leak.

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Wednesday, February 6th, 2013 AT 2:42 PM
  • Tiny
  • chrishurssey
  • Member

No I doubt if I have a leak because it worked just fine yesterday and I know it is an electrical problem because my blower fan will not turn on I also checked the power line that goes to my ac and it is not reading any voltage. Also I checked all the fuses and they all worked fine. But I kno it is an electrical problem what should I do.

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Wednesday, February 6th, 2013 AT 5:24 PM
  • Tiny
  • hmac300
  • Expert
  • 41,621 posts

We have no diagrams of this it's just to old. I do have a 1976 ford manual which will be similar. This system runs off of vacuum and electric and one of the things that made this system not cool was no vacuum to the water shutoff valve underhood. Or the vavle went bad. There is a compressor clutch switch at back of control head that mmay or may not being applied by contorl head check behind control to see if poer is coming in to swith because if it is then it's a switch problem If i'm right the blower switch feed the clutch switch so if one is gone the other won't work. There is a fusible link on the starter relay to protect the a/c it should be a 16 guage fusiblelink however I don't know what color it is it could be yellow orange or brown a test light wold be all you need to check it with pushing test light to oppisite side of link. They are availabe at auto parts Other than that due to the age of htis truck you'll hav eto find an electrical manual for thatyear for specific color wire

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Wednesday, February 6th, 2013 AT 5:54 PM
  • Tiny
  • chrishurssey
  • Member

Ok can you tell me where the control head is located. And if you can is there some way you can post a picture of the ac/heater pages in that 1976 ford manual I would really apreciate it.

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Wednesday, February 6th, 2013 AT 6:16 PM
  • Tiny
  • hmac300
  • Expert
  • 41,621 posts

The control head is in the dash the part that you turn the a/c on and blower on but check the fusible link on starter relay first and no I can't post apic from that manual

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Wednesday, February 6th, 2013 AT 6:19 PM
  • Tiny
  • chrishurssey
  • Member

Ok thanks I will soon have more questions.

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Wednesday, February 6th, 2013 AT 7:38 PM

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