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JW in MO 
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Joined: 16 Feb 2010
Location: South KC Area
Points: 2618
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 Topic: Air Cond. problems in my truck
Posted: 06 May 2018 at 8:15pm |
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05 Silverado 3500, ran the a/c last weekend and worked just fine, today not so much. Compressor won't kick on, system has plenty of pressure, fuses good, if I manually make the relay contacts the compressor runs. I have 12v to the relay coil but not a ground. I have swapped relays with a known working one and nothing. I have manually jumpered the low and high pressure switch individually but nothing. I noticed a check engine light, diagnostic said low voltage circuit B, cleared the fault, nothing. Is there another pressure switch besides the one on the accumulator tank and on the discharge line?
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Clay
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Joined: 11 Sep 2009
Location: Udall, Kansas
Points: 9323
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Posted: 06 May 2018 at 10:06pm |
Have you put a code reader on the truck?
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JW in MO
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Joined: 16 Feb 2010
Location: South KC Area
Points: 2618
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Posted: 07 May 2018 at 7:31pm |
 Clay wrote:
Have you put a code reader on the truck? |
That's how I got "I noticed a check engine light, diagnostic said low voltage circuit B, cleared the fault, nothing."
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steve(ill)
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Joined: 11 Sep 2009
Location: illinois
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Posted: 07 May 2018 at 7:39pm |
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Wendell, I don't claim to know anything about that truck... but on many FORDS there is power to the switch / blower / fan etc... and the dash knob when rotated completes the GROUND CIRCUIT..... Many times people are looking for the switch to supply POWER to a component, when actually it forms the GROUND.......... bad switch or ground wire ??
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Like them all, but love the "B"s.
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JW in MO
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Joined: 16 Feb 2010
Location: South KC Area
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Posted: 07 May 2018 at 8:36pm |
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Yeah, that's kinda where I'm at, after rechecking the pressure switches with a test light they don't have voltage so I'm just guessing that they are on the ground circuit since I have 12 volts to the relay coil.
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Tbone95
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Joined: 31 Aug 2012
Location: Michigan
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Posted: 08 May 2018 at 7:55am |
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Is the blower working?
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JW in MO
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Joined: 16 Feb 2010
Location: South KC Area
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Posted: 08 May 2018 at 8:05am |
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Yes, blower works, snowflake appears when I turn it on.
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Brian Jasper co. Ia
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Joined: 11 Sep 2009
Location: Prairie City Ia
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Posted: 08 May 2018 at 8:10am |
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It has a trinary switch on the high side. You need to look at the data for the system. Sounds like you have a malfunction like the 5v ref side down or shorted to ground and the ECM is withholding compressor operation.
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"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford
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JW in MO
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Joined: 16 Feb 2010
Location: South KC Area
Points: 2618
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Posted: 08 May 2018 at 8:37pm |
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Well I went out tonight armed with a wiring diagram and a meter, started the truck and the A/C worked just fine. I never moved it or anything since the last episode. Now I know it aint like a sore thumb and just up and healed itself but I am going to be prepared. Only sure way I know to make it happen again is. . . . Hey Maddux, want to go on a road trip?
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john(MI)
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Joined: 12 Sep 2009
Location: SE MI
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Posted: 09 May 2018 at 9:05am |
We used to roll down the windows for the AC! 
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D14, D17, 5020, 612H, CASE 446
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shameless dude
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Joined: 10 Apr 2017
Location: east NE
Points: 13607
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Posted: 09 May 2018 at 11:54am |
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lol....I was in town the other day and stopped at the gas station, a dude asked me why I had my windows rolled up on such a hot day? told him so the ac cool won't get out! he said (with a funny look on his face) that old truck has a working ac???? told him..yeah don't yers? (he had a pretty new truck) he said his quit the year before and figgered it was done. said he might see if he can gits it fixed. yeah Les and Joe...it was a newer ferd pickup!
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