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Had a buddy bring me his car saying his a/c is blowing warm after he replaced the blower motor and resistor (Probably just bad timing). He said the a/c was blowing nice and cool prior to putting those parts in.
When i checked it out i noticed the clutch not engaging, checked fuses and relays, all is well. I checked pressures, was a bit low so I evac'd and recharged the system. Still not getting clutch to engage.
I have access to scan tools and such so hooked up and commanded the clutch to engage and it kicked on. I then checked the data for the clutch command and high fan command, neither are being commanded on even with the a/c button pressed and light illuminated on the button. If i command the clutch on with the scan tool while the low fan is on, the ac blows cold, but the high side pressure eventually rises to near 400psi before I have to command it off.
If anyone has any insight on where to look next, or what possible reason the pcm is not commanding either the clutch or high fan on when ac button is pressed please do feel free to comment.
Any other questions that may help i'd be happy to answer to the best of my knowledge. Thanks.
I can think of a few quick checks with the scan tool. I'm guessing the system pressures looked reasonable on the manifold gauges, but what about the A/C pressure sensor on the car? Does it agree with your gauges?
Another quick check would be the evaporator temp sensor reading. If it's too low, clutch operation will be withheld to prevent icing the evaporator.
Does the Air Conditioning Request Signal PID in the PCM change while pushing the A/C button on the dash?
With a test light or a volt meter check right at the Compressor connector for proper power and ground. Here’s a diagram if that ends up checking out. Not much to the circuit.
Can you communicate with the HVAC module?
Making Pressure Differential Sensors (PDA Sensors) for pressure pulse diagnostics.
Currently servicing Central Texas.
Don't be so quick to dismiss the blower and "resistor" replacement as "bad timing". Seems unlikely that a '13 would have a dumb, resistor based, blower speed control. See if you can find any blower PIDs. Might even be a blower code set which is inhibiting AC operation.
Hardtopdr2 wrote: I would start with the work that was just done check the connectors and wiring to see if he forgot a connector or if a wire got pinched or broken.
I went down and pulled the connectors off of both just and checked for any burnt pins or a burning smell and all looks good, the other wiring in that harness goes to the actuators and those are functioning. Only other that i can see is the EVAP temp sensor which another member has suggested looking, which i haven't. Thank you for the suggestion.
Tyler wrote: I can think of a few quick checks with the scan tool. I'm guessing the system pressures looked reasonable on the manifold gauges, but what about the A/C pressure sensor on the car? Does it agree with your gauges?
Another quick check would be the evaporator temp sensor reading. If it's too low, clutch operation will be withheld to prevent icing the evaporator.
Does the Air Conditioning Request Signal PID in the PCM change while pushing the A/C button on the dash?
System pressures were around 150 on both sides, it was about 105 out and 30-40% humidity (i believe) so i didn't think that was too crazy of a number to see. The pressure sensor on the vehicle according to the scan tool was similar to what the gauge was showing, maybe a 5-10% difference, but really close at all times.
I didn't think to check the evap temp sensor! That is something i will look at when he brings me the vehicle back in a day or two. The A/C request signal does not change at all when the a/c button is pressed, neither that or the high side fan is being requested on when the a/c button is pressed and illuminated.
John Curtis wrote: With a test light or a volt meter check right at the Compressor connector for proper power and ground. Here’s a diagram if that ends up checking out. Not much to the circuit.
Can you communicate with the HVAC module?
I kind of skipped the step of manually checking power and ground at the compressor connector, I assumed those were good since the clutch kicks on when manually commanded to do so with the scan tool. (Maybe I should stop the assuming)
I didn't try to directly communicate with the HVAC module, I will see if that's a possibility with the scan tool I have when he brings me the vehicle again. I was going through the PCM since that's where the option was to test the compressor clutch. Also, thank you for the diagram, that's quite thoughtful of you to take the time to attach for me.
Last edit: 5 years 1 month ago by Dozamen. Reason: !
Dozamen wrote: I didn't think to check the evap temp sensor! That is something i will look at when he brings me the vehicle back in a day or two. The A/C request signal does not change at all when the a/c button is pressed, neither that or the high side fan is being requested on when the a/c button is pressed and illuminated.
No worries. If the request PID never changed, then I'd start talking to the HVAC module and figure out why it's withholding compressor engagement.
Keep your eyes open for irrational readings and the like. Evap temp and outside/ambient temp are prime suspects.
If the HVAC says it's requesting compressor engagement but the PCM didn't get the memo... That's an entirely different problem. :silly:
Matt T wrote: Don't be so quick to dismiss the blower and "resistor" replacement as "bad timing". Seems unlikely that a '13 would have a dumb, resistor based, blower speed control. See if you can find any blower PIDs. Might even be a blower code set which is inhibiting AC operation.
I'll dig deeper into the blower motor and resistor part of things when i get the vehicle back. There were no codes in the vehicle while I had it but who know, maybe something will pop in.
Tyler wrote: No worries. If the request PID never changed, then I'd start talking to the HVAC module and figure out why it's withholding compressor engagement.
Keep your eyes open for irrational readings and the like. Evap temp and outside/ambient temp are prime suspects.
If the HVAC says it's requesting compressor engagement but the PCM didn't get the memo... That's an entirely different problem. :silly:
Maybe I was chasing the wrong dog, I didn't once look at the readings for evap and ambient temps, my next direction was going to that a/c button and seeing if i was actually getting anything being output directly from that. I don't do a ton of a/c work but i've also never been thrown for a loop like this over it either haha. I appreciate the help and ideas from everyone.
Dozamen wrote: I'll dig deeper into the blower motor and resistor part of things when i get the vehicle back. There were no codes in the vehicle while I had it but who know, maybe something will pop in.
It'd be good to know why they were replaced and whether they were replaced with OEM or aftermarket.....
Did you scan all modules or just the PCM? BTW if your scan tools can't talk to the HVAC module Forscan is worth a shot. Windows version was free last I heard but I think they charge a few bucks for the phone apps. Then just need a compatible bluetooth or USB adapter which isn't expensive if you don't already have one.
From what i came across while drowning some bait at the lake. (Albeit this diagram is 2011) is the blower motor is pwm controlled not a resistor type setup so it could be that controller he put in if he has the old one still swap it out and see if it functions like before if not then back probe pwm wire and see what it looks like on a scope. New parts can be bad parts as from what i have seen. As far as getting 400 psi on high side and static pressure of 150 psi both sides i think it may be overcharged cause when the high side gets to 430 psi the high pressure switch disables the air conditioning. What was low side pressure when high side was at 400 btw this part seams like a txv valve sticking. The most you should see for pressure on the high side at 105f is 330-335psi while low side should be 50-55psi at 105f.
Hardtopdr2 wrote: From what i came across while drowning some bait at the lake. (Albeit this diagram is 2011) is the blower motor is pwm controlled not a resistor type setup so it could be that controller he put in if he has the old one still swap it out and see if it functions like before if not then back probe pwm wire and see what it looks like on a scope. New parts can be bad parts as from what i have seen. As far as getting 400 psi on high side and static pressure of 150 psi both sides i think it may be overcharged cause when the high side gets to 430 psi the high pressure switch disables the air conditioning. What was low side pressure when high side was at 400 btw this part seams like a txv valve sticking. The most you should see for pressure on the high side at 105f is 330-335psi while low side should be 50-55psi at 105f.
This was it, I called him and asked if he still had the original part and told him to throw it back in, worked like a charm. He said the blower motor would cut out on him a lot lately so he changed both parts. I didn't realize it was a pwm controlled. I'll be sure to pay closer attention to things in the future. Thank you for your input, definitely saved me a headache.
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If the request PID never changed, then I'd start talking to the HVAC module and figure out why it's withholding compressor engagement.