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93 sierra c1500 a/c wiring issue
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james091104
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Aug 12, 2013, 11:26 AM
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93 sierra c1500 a/c wiring issue
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I have a 1993 GMC Sierra c1500 4.3 liter. On the climate control wiring there is a red wire that is over heating. The wire connects to the power distribution block under the hood, the climate control, and from the wiring diagram it connects to the blower relay. I am not positive to the third connection point, because the three relays for the blower are right behind the dash and the red wire doesn't seem to connect to them. What would cause this wire to over heat at the wiring harness connection located between the blower relays and the cpu behind the glove box, the harness includes the green and dark green wires? Also, this harness is the connection point that goes through the firewall.
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Hammer Time
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Aug 12, 2013, 11:46 AM
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Re: 93 sierra c1500 a/c wiring issue
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That is the power supply to your blower. The blower motor is probably shot and drawing too much current. You can do a draw test on it to find out.
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Discretesignals
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Aug 12, 2013, 5:58 PM
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Re: 93 sierra c1500 a/c wiring issue
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That wire can also get hot if there is excessive resistance in the wiring itself. Blower motor is trying to pull current through a wire or connector that has resistance and the wire is going to heat up.
You should run a voltage drop test of that wire to see if there is excessive resistance in it.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Aug 12, 2013, 5:59 PM)
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Hammer Time
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Aug 12, 2013, 6:20 PM
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Re: 93 sierra c1500 a/c wiring issue
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Sure........ who cares how much current the blower is pulling.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
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Aug 12, 2013, 6:24 PM
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Re: 93 sierra c1500 a/c wiring issue
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The wiring heating up isn't from the blower. If the blower was pulling too much current it would pop the fuse before melting the wiring.
Wiring or connectors getting hot and cooking is caused by resistance in the wiring or connections. Do you replace the blower every time you get a C truck in for melted blower resistor connectors?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Hammer Time
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Aug 12, 2013, 6:27 PM
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Re: 93 sierra c1500 a/c wiring issue
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It's not melting the wire. It's merely getting hot. Draw 22 amps consistently on a 25 amp circuit and it will get warm. I can't see an entire length of wire having to much resistance, one connection maybe.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
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Aug 12, 2013, 6:45 PM
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Re: 93 sierra c1500 a/c wiring issue
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If that is true, why isn't the ground wire a the blower getting hot since current is the same in the entire circuit?
If there is a connection, lets say at the pass thru at the firewall, that has a bad connection due to resistance in a terminal, the wire is going to get hotter the closer you get to the bad connection. Copper is a good conductor of heat.
Easy way to prove it is to turn the blower on high, connect your volt meter red to the purple wire at the blower connector. Then connect black lead to the positive side of the battery. You see more than 1/2 volt, you got an issue in the wiring harness somewhere.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Aug 12, 2013, 6:50 PM)
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james091104
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Aug 16, 2013, 5:22 PM
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Re: 93 sierra c1500 a/c wiring issue
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Thank you for your time in helping me resolve this issue. the connector with the red, green, and dark green wires had a bad connection on one side of the red wire. I do still have a question. Where did you get the information about the voltage reading of 1/2 volt or greater showing that a wiring problem exists?
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Hammer Time
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Aug 16, 2013, 5:48 PM
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Re: 93 sierra c1500 a/c wiring issue
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That's a standard voltage drop test.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
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Aug 16, 2013, 5:49 PM
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Re: 93 sierra c1500 a/c wiring issue
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I kind of threw that number out there because I knew you would see over it with a hot wire going on. For battery cables it shouldn't be more than 0.5 volt. Normal wiring for lamps and stuff like that is around 0.3 volts. Computer wiring around 0.1 volts. Those are just general rules of thumb and aren't concrete.
The information was learned from various sources that I can't even remember anymore. Any tech involved with diagnosing electrical problems has to have a basic understanding of testing volt drops in high amp circuits to find areas of high resistance that you probably won't find with an ohm meter.
If you Google voltage drop testing, there are hundred of sites with info on it. You can also Youtube voltage drop testing if you prefer watching videos.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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james091104
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Aug 17, 2013, 12:51 PM
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Re: 93 sierra c1500 a/c wiring issue
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Thank you Discretesignals. Your information is very informative.
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Hammer Time
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Aug 17, 2013, 3:18 PM
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Re: 93 sierra c1500 a/c wiring issue
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
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Aug 17, 2013, 6:02 PM
Post #13 of 13
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Re: 93 sierra c1500 a/c wiring issue
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Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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