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A/C system

Tiny
URSULOROBLES
  • MEMBER
  • 1999 FORD F-350
  • 6.2L
  • V8
  • 2WD
  • AUTOMATIC
  • 38,400 MILES
The air conditioner does not work; the blower does not work. If I put voltage on compressor clutch, a/c clutch engages. I checked the blower and I put voltage on blower and it works too. Thanks in advance.
Tuesday, April 4th, 2017 AT 4:06 PM

16 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
I am assuming system has been checked for Freon it may be bad pressure switch on front of firewall if system is low or to low of pressure to run you will run into this problem. Check fuses 22-23-24 two are inside truck one is under hood. Then check blower relay under hood as well.
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Wednesday, April 5th, 2017 AT 7:41 AM
Tiny
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  • 47 POSTS
When I turned on the compressor with voltage the a/c cooled very well. I will check the fuses; where is the blower relay under the hood? Right side next to accumulator box? How do I check the blower relay?
Thanks in advance.
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Wednesday, April 5th, 2017 AT 1:49 PM
Tiny
HMAC300
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The blower relay is in the pdc underhood with fuses. see link it still can be a bad pressure switch as well.
https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit
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Wednesday, April 5th, 2017 AT 3:23 PM
Tiny
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My motorhome is a 1990 Ford Chassis 27 ft. Kountry Star with 460 engine. It does not have a PDC under the hood, the fuses under the dashboard are okay, anything else, how can I test the a/c for no power to compressor and fan blower speed.
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Thursday, April 6th, 2017 AT 10:01 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Well if you said it was motor home at first then I could have looked up correct diagram. It may not be factory air in that thing. Is it a van front end with the motor home attached? If what is called just a chassis then it won't have factory air in it and will be from another manufacturer
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Thursday, April 6th, 2017 AT 10:33 AM
Tiny
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NO, Newmar Mfg. Co. Built it with a 1990 Ford chassis with the original Ford engine (460) and original a/c system and Ford auto trans.
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Thursday, April 6th, 2017 AT 12:41 PM
Tiny
HMAC300
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  • 48,601 POSTS
Ok so it has a factory unit But does it have the ford van front end or is it just a ford chassis or if you know whether it is a class A or class C then I would know
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Thursday, April 6th, 2017 AT 12:59 PM
Tiny
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  • 47 POSTS
Class A motor home
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Thursday, April 6th, 2017 AT 1:23 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Ok now that we know what we are dealing with again I am assuming system is full. Arrow points to the clutch cycling switch which is located on the accumulator. I t looks like a tall can where pipes go in it will have a large pipe for a/c going to it. Fuse 9 controls a/c. Jump the wire and see if compressor starts if not then it's a wiring problem or diode on compressor but in previous replies you said if you power up compressor it will work. If system is not full that is why compressor doesn't work and Freon has leaked out. You will have to refill system with R134 instead of R12 because 12 is very expensive
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Thursday, April 6th, 2017 AT 4:13 PM
Tiny
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The a/c compressor is coming on after I replaced the accumulator switch. Yet, the fan blower does not come on with any speed on blower switch with a/c or vent on, if I connect voltage to fan blower under hood, the fan works on any speed.
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Thursday, April 6th, 2017 AT 5:29 PM
Tiny
HMAC300
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That is either the relay or a bad fusible link it is on rh side of engine compartment above headlight. Links are attached to starter relay and should have 12v on both sides. Pic in next email
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Friday, April 7th, 2017 AT 6:32 AM
Tiny
HMAC300
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See pic
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Friday, April 7th, 2017 AT 6:33 AM
Tiny
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I have checked the fusible links and they have voltage on both sides; the relay has 4 wires, solid yellow, solid red, brown w/blue stripe and orange w/ blue stripe. What should the voltages on each wire with key on? Thanks
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Saturday, April 8th, 2017 AT 1:58 PM
Tiny
HMAC300
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Yellow wire should have power then orange/red in pic you will see another fusible link blue if no power at yellow check that. Although relay could be bad, now that I remember that was a common failure on fords was the relay. But that was 30 some years ago. For me lol
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Saturday, April 8th, 2017 AT 3:33 PM
Tiny
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The yellow wire has powerw/o and with key on, the other wires except orange w/ blue stripe have power, does the orange w/blue stripe have a fusible link?
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Saturday, April 8th, 2017 AT 4:51 PM
Tiny
HMAC300
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  • 48,601 POSTS
Forgot to load the damn pici don't show orange/blu I show orange/red which goes to blower if no power there then relay is no good yellow/red shold have power when a/c is turned on.
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Saturday, April 8th, 2017 AT 4:57 PM

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