Morganne222
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- Apr 20, 2015
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I am having some electrical issues in my truck, and am wondering if the problems are related.
I have badly flickering cluster lights, headlights that flicker but not noticeably (noticed only when assessing cluster light issue), and I am getting no a/c compressor clutch engagement unless I jump it manually.
Replaced the battery (2014 Fall)
Alternator is OE but have had it tested twice.
One =good.
Other = good but tech said "hardly noticeable" fluctuation only seen by computer testing.
I am hesitant to "shotgun" it due cost. Nor do I want to take it to a shop because they have to do a $200 A/C leak dye test by law in WI before they touch the unit.
I am a college student and would rather just spend the money on parts and invest time than diagnosis/labor/parts cost from shop. I am also a sophomore year engineering major specifying in mechanized systems so I enjoy this as well. I have an OK grasp on electrical systems, I can use a multimeter and understand diagrams but I like to understand what I am doing before I start fiddling with currents that could ruin my truck. I have tried a few things but I would like to be thorough.
-A/C Compressor Jump at the Accumulator, the clutch engaged.
-DIY Recharge to bring up pressure to eliminate the pressure cutout activation, no electrical engagement
also when the truck was turned off I noticed the pressure valves (low and high) were releasing pressurized air, I also didn't vacuum pump the system so I think that we pumped it a little high, as my boyfriend "knew what he was doing" and "did it before" same old same old lol.
-Replaced Pressure Switch as a precaution because I am able to jump the relay
-LED gauge lights (194) in the dash and an aftermarket radio (didn't alter GM harness)
-Cleaned and inspected all fuses
-Replaced blower motor resistor and did test on all connections to it from the HVAC
-I also used my ohm meter to make sure the new low pressure switch actually works and it circulates electricity. when the pos and neg are touching opposite prongs. I am going off of a forum that explained it in low detail so I am not sure if that is an accurate assessment and if I am absolutely off base then please correct me lol.
I plan to test engine bay fuse box terminals for relay issues, compressor grounds especially the ones shared by cycling switch and cutout switch, and the a/c push button connection from HVAC panel to VCM, since my HVAC controls seem to work the A/C by pushing the air out a little harder I am hesitant to waste time on assessing the circuit board for a blown transistor
Here is a article that explained the pin jump in the fuse box to test the relay. If the relay wasn't working then I wouldn't be able to engage the clutch by jumping it, at least to my understanding, which would make this test irrelevant. But I am not sure if I am missing something. I also attatched the A/C wiring diagram
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TESTING AC RELAY.
With the key on, engine off, momentarily jump the A/C clutch relay from pin 30 to pin 87, the Compressor clutch should "click". If no click, unplug the clutch connector, jumper pin 30 to pin 87, check for power at the green wire at the compressor. Check the black wire for ground.
Forcing the AC relay to engage bypasses the control head, and will make the compressor run continuously. If the compressor runs with the relay forced on, the Heater AC Control Unit may be bad, or the pressure switches may not be closed.
Use a voltmeter, check terminal #85 in the socket (should be the lower right hand corner if standing on the drivers side looking down on the relay/fuse center) changes voltage when the AC button is pressed. The engine should be running. The Heater AC Control Unit switches terminal #85 to complete the circuit for the coil in the relay. With AC on from the Control Unit, #85 should have +12V, and #86 is ground for the relay coil.
Applying power to terminal #30 with the relay unplugged will engage the compressor clutch. Check for power at #87; it is the power for the clutch circuit. This is what is switched to #30 to power the clutch circuit.
I have badly flickering cluster lights, headlights that flicker but not noticeably (noticed only when assessing cluster light issue), and I am getting no a/c compressor clutch engagement unless I jump it manually.
Replaced the battery (2014 Fall)
Alternator is OE but have had it tested twice.
One =good.
Other = good but tech said "hardly noticeable" fluctuation only seen by computer testing.
I am hesitant to "shotgun" it due cost. Nor do I want to take it to a shop because they have to do a $200 A/C leak dye test by law in WI before they touch the unit.
I am a college student and would rather just spend the money on parts and invest time than diagnosis/labor/parts cost from shop. I am also a sophomore year engineering major specifying in mechanized systems so I enjoy this as well. I have an OK grasp on electrical systems, I can use a multimeter and understand diagrams but I like to understand what I am doing before I start fiddling with currents that could ruin my truck. I have tried a few things but I would like to be thorough.
-A/C Compressor Jump at the Accumulator, the clutch engaged.
-DIY Recharge to bring up pressure to eliminate the pressure cutout activation, no electrical engagement
also when the truck was turned off I noticed the pressure valves (low and high) were releasing pressurized air, I also didn't vacuum pump the system so I think that we pumped it a little high, as my boyfriend "knew what he was doing" and "did it before" same old same old lol.
-Replaced Pressure Switch as a precaution because I am able to jump the relay
-LED gauge lights (194) in the dash and an aftermarket radio (didn't alter GM harness)
-Cleaned and inspected all fuses
-Replaced blower motor resistor and did test on all connections to it from the HVAC
-I also used my ohm meter to make sure the new low pressure switch actually works and it circulates electricity. when the pos and neg are touching opposite prongs. I am going off of a forum that explained it in low detail so I am not sure if that is an accurate assessment and if I am absolutely off base then please correct me lol.
I plan to test engine bay fuse box terminals for relay issues, compressor grounds especially the ones shared by cycling switch and cutout switch, and the a/c push button connection from HVAC panel to VCM, since my HVAC controls seem to work the A/C by pushing the air out a little harder I am hesitant to waste time on assessing the circuit board for a blown transistor
Here is a article that explained the pin jump in the fuse box to test the relay. If the relay wasn't working then I wouldn't be able to engage the clutch by jumping it, at least to my understanding, which would make this test irrelevant. But I am not sure if I am missing something. I also attatched the A/C wiring diagram
-------------
TESTING AC RELAY.
With the key on, engine off, momentarily jump the A/C clutch relay from pin 30 to pin 87, the Compressor clutch should "click". If no click, unplug the clutch connector, jumper pin 30 to pin 87, check for power at the green wire at the compressor. Check the black wire for ground.
Forcing the AC relay to engage bypasses the control head, and will make the compressor run continuously. If the compressor runs with the relay forced on, the Heater AC Control Unit may be bad, or the pressure switches may not be closed.
Use a voltmeter, check terminal #85 in the socket (should be the lower right hand corner if standing on the drivers side looking down on the relay/fuse center) changes voltage when the AC button is pressed. The engine should be running. The Heater AC Control Unit switches terminal #85 to complete the circuit for the coil in the relay. With AC on from the Control Unit, #85 should have +12V, and #86 is ground for the relay coil.
Applying power to terminal #30 with the relay unplugged will engage the compressor clutch. Check for power at #87; it is the power for the clutch circuit. This is what is switched to #30 to power the clutch circuit.
