A/C Sporadically Cools
07-13-2016, 08:12 AM
#21
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Join Date: 01-23-2009
Location: Fredericksburg,VA
Posts: 24,900
Re-mating the box has been a problem in the past.
I really think too many mechanics blame "computers" too fast.
The button signals the BCM. The BCM sends a serial data signal to the ECM.
The ECM receives a signal from the pressure switch and the engine temp sensor.
The ECM send a relay control (ground) to the relay. The relay energizes the compressor clutch.
Parts that could go bad: engine temp sensor, refrigerant pressure switch, A/C switch, compressor clutch, relay. Or any wire.
BCM fuse #16 & #10
Under hood fuse #22 & relay #15
OR; some occasional OBD fault that has not set a CEL. Some require more than 1 instance in a drive cycle, some require a repeat in consecutive drive cycles, some only one time.
3 kinds of codes: current, pending, historical. Your reader may use different words.
Current means it happened once, pending means it's waiting for another occurrence, historical means it has caused a CEL. When a CEL is set the computer store a "freeze frame" which shows the sensor readings at the time of the CEL.
I just don't see the BCM as a suspect. The ECM supplies GROUND to the coil of the relay. You could test the relay by jumping pin 87 and pin 30 (on the fuse box) and see if the clutch is getting power.
Have I confused you enough?
I really think too many mechanics blame "computers" too fast.
The button signals the BCM. The BCM sends a serial data signal to the ECM.
The ECM receives a signal from the pressure switch and the engine temp sensor.
The ECM send a relay control (ground) to the relay. The relay energizes the compressor clutch.
Parts that could go bad: engine temp sensor, refrigerant pressure switch, A/C switch, compressor clutch, relay. Or any wire.
BCM fuse #16 & #10
Under hood fuse #22 & relay #15
OR; some occasional OBD fault that has not set a CEL. Some require more than 1 instance in a drive cycle, some require a repeat in consecutive drive cycles, some only one time.
3 kinds of codes: current, pending, historical. Your reader may use different words.
Current means it happened once, pending means it's waiting for another occurrence, historical means it has caused a CEL. When a CEL is set the computer store a "freeze frame" which shows the sensor readings at the time of the CEL.
I just don't see the BCM as a suspect. The ECM supplies GROUND to the coil of the relay. You could test the relay by jumping pin 87 and pin 30 (on the fuse box) and see if the clutch is getting power.
Have I confused you enough?
07-13-2016, 09:57 AM
#22
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Join Date: 10-13-2011
Location: Welland,Ont Canada
Posts: 36,836
So eliminate the possibility of a bad thermostat and the wrong coolant!! Both could contribute to the AC issue!
Clean the connections then reconnect, depending on the grease you used it might not be dielectric!
Clean the connections then reconnect, depending on the grease you used it might not be dielectric!
07-13-2016, 11:19 AM
#23
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Join Date: 05-01-2014
Location: California
Posts: 7,896
There is much debate about dielectric grease. Most sources claim that it has insulating properties. In the future, when we refer people to that video for the fusebox, we should caution them to not use any grease, or to make sure it is a conductive grease.
07-13-2016, 11:28 AM
#24
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07-13-2016, 05:16 PM
#26
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Thread Starter
Join Date: 01-26-2016
Location: Saint Louis, MO
Posts: 166
Wow - thanks, guys!
I know for sure that I used dielectic grease, as it says "dielectric grease for electrical connections" on it. I used it sparingly too. I guess if I need to clean the grease OFF those blades, I should also clean out the receiving end too, right? ...is brakeclean ok to use?? (I learned a LOT with that video on spark plugs-thanks!)
Will try jumping those connectors - thanks much!
And of course, DexCool and a thermostat are on the radar now too.
Thanks very much for your input, gentlemen!
I know for sure that I used dielectic grease, as it says "dielectric grease for electrical connections" on it. I used it sparingly too. I guess if I need to clean the grease OFF those blades, I should also clean out the receiving end too, right? ...is brakeclean ok to use?? (I learned a LOT with that video on spark plugs-thanks!)
Will try jumping those connectors - thanks much!
And of course, DexCool and a thermostat are on the radar now too.
Thanks very much for your input, gentlemen!
07-13-2016, 07:41 PM
#27
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Join Date: 01-23-2009
Location: Fredericksburg,VA
Posts: 24,900
Read the other link Oldblue posted, it is basically the opposite of the youtube.
Dielectric Grease vs Conductive Grease
Dielectric Grease vs Conductive Grease
07-13-2016, 09:01 PM
#28
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Join Date: 05-01-2014
Location: California
Posts: 7,896
Read the other link Oldblue posted, it is basically the opposite of the youtube.
Dielectric Grease vs Conductive Grease
Dielectric Grease vs Conductive Grease
Dielectric by definition has to do with insulating. In plumbing, a dielectric union is installed between 2 dissimilar metals to help insulate, or at least minimize, galvanic corrosion, which is an electro-chemical process.
There is a lot I don't understand about this, but didn't the manufacturer make these connections dry? Problem is the connections were sometimes left loose.
07-13-2016, 09:41 PM
#29
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Join Date: 01-23-2009
Location: Fredericksburg,VA
Posts: 24,900
The dielectric that the grease is talking about is the type that causes corrosion, not the kind that makes things work. It is also used in plumbing and electrical wiring when mating 2 unlike metals; I.E.: copper wire to aluminum wire, or copper pipe to galvanized pipe.
Ion transfer and that science stuff that Walter White does. (I've finally gotten around to watching Breaking Bad.)
Ion transfer and that science stuff that Walter White does. (I've finally gotten around to watching Breaking Bad.)
07-16-2016, 04:11 AM
#30
Senior Member
Thread Starter
Join Date: 01-26-2016
Location: Saint Louis, MO
Posts: 166
Hey DonBrew, that relay image that you posted above - I just find the relay for the clutch and then identify the pins (87 & 30) based on the configuration? ...no "87" on my fuse box...
I removed the dielectic grease carefully and reassembled. Headlights etc work again. The a/c even functioned upon startup...then resumed its sporadicity (how's THAT for a new word).
I bought my Dexcool and AC-Delco thermostat (WHY on earth is that thing $50!?!? the ONLY reason I'm spending 3X necessary is because I trust all you guys) -- hope to flush and install within the next several days. The SS thermostat looks WAY more difficult than the others, but I should be able to handle it.
Hey - the bolts that are in the fuse panels - they "CLICK" kinda loud if you snug 'em too tight and then are loose again... tighten again and try not to do too tight. I couldn't see any sign of stripped threads in the brass receiver-part or on the bolts... but did I break something?
Thanks again guys.
I removed the dielectic grease carefully and reassembled. Headlights etc work again. The a/c even functioned upon startup...then resumed its sporadicity (how's THAT for a new word).
I bought my Dexcool and AC-Delco thermostat (WHY on earth is that thing $50!?!? the ONLY reason I'm spending 3X necessary is because I trust all you guys) -- hope to flush and install within the next several days. The SS thermostat looks WAY more difficult than the others, but I should be able to handle it.
Hey - the bolts that are in the fuse panels - they "CLICK" kinda loud if you snug 'em too tight and then are loose again... tighten again and try not to do too tight. I couldn't see any sign of stripped threads in the brass receiver-part or on the bolts... but did I break something?
Thanks again guys.