What is this?
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From: Walterboro, SC
What is this?
And did I mess something up? This is about six inches down from the A/C Compressor connection on my truck.
Last edited by nothingbutford; Apr 27, 2004 at 07:13 AM.
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Senior User
Joined: Jul 2001
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From: Walterboro, SC
Yes, it's the wiring harness going to the AC compressor. I was tracing the wires back looking for bare spots and took that apart too. The bad part is I broke the leads on the diode or whatever it is (DUMB!) I guess I messed something up huh? I was mainly wondering why that is there and what it does. Just to understand it a little better. I'm taking a trip to the junkyard soon to try and find another wiring harness section.
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The ac clutch is a coil, that when it gets current, magnetizes and engages the compressor. All coils are somewhat like capacitors. When they are energized, they develop a magnetic field around them. You can think of this field as stored energy like would be in a large capacitor.
When the voltage is taken off the coil, the field around the coil collapses, and all this stored energy runs backwards up through the circuit that feeds the coil. This backwards "spike" can damage the circuit that feeds the coil. So the diode is placed across the coil wires, to take out this spike of voltage.
The voltage feeding the coil has a + and a - polarity. The diode is like a electronic check valve, it will only let voltage flow one direction. And it just so happens the backward spike has reverse polarity. So the diode is placed backwards to the flow of normal current, but when the spike comes back through in reverse, the diode looks like a short, and kills the spike.
When the voltage is taken off the coil, the field around the coil collapses, and all this stored energy runs backwards up through the circuit that feeds the coil. This backwards "spike" can damage the circuit that feeds the coil. So the diode is placed across the coil wires, to take out this spike of voltage.
The voltage feeding the coil has a + and a - polarity. The diode is like a electronic check valve, it will only let voltage flow one direction. And it just so happens the backward spike has reverse polarity. So the diode is placed backwards to the flow of normal current, but when the spike comes back through in reverse, the diode looks like a short, and kills the spike.
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From: Walterboro, SC
Thanks, That's cool. I understand about energized coils producing magnetic fields and charging & discharging capacitors. I had alot of that in Physics. They never taught me about diodes though. So I guess I better be finding a replacement harness or take mine to a computer shop and see if they will patch it for me. I wish I had known this BEFORE I messed with it. Thanks again.
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