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A/C electrical gurus unite, The dead horse that needs beating
Mechanical Problems/Vehicle Issues and Fix-it ForumIf you've got a problem you just can't figure out, a noise you can't diagnose, or a Check Engine Light that won't go away, ask about it here!
A/C electrical gurus unite, The dead horse that needs beating
THERE IS SHORTER VERSION OF DIAGNOSIS A FEW POSTS DOWN FOR PEOPLE NOT USING THIS AS A GUIDE
I do HVAC for a living, commercial, residential, and I've fixed quite a few vehicles, this 2001 civic ex has really got me ready to quit the game. The car is a friends, I replaced the discharge line, the compressor, the drier, and the expansion valve, pulled a vacuum, dumped some liquid in, turned on the system on, got nothing. Jump the neg terminal of relay ground to battery ground, get nothing, do some light reading, realize he has some other issues that point to multiplex unit, order new multiplex unit, things start working..... except the a/c. Heres where I am
A/C compressor Clutch Circuit Troubleshooting
NOTE:
- Do not use this troubleshooting procedure if the (radiator and condenser) fans are also inoperative with the A/C on.
- Before performing symptom troubleshooting, check for powertrain DTC's. (scan the car)
1. Check the #1 (20 amp) fuse under the hood, and the #14 (10 amp) fuse under the dash. both good
Are the fuses okay?
Yes - Go to step 2.
No - Replace the fuse(s) and recheck.
2. Check the engine coolant temperature, throttle position, and idle speed. (use the HDS PGM-FI data list if possible)
ECT Sensor: 169 - 194 degrees
TPS: About 0.5 volts
RPM: More than 700
Are the coolant temperature, throttle position, and idle speed okay? All Good
Yes - Go to step 3.
No - Troubleshoot and repair the cause of the high engine coolant temperature, low idle, or excessively high throttle position sensor reading.
3. Remove the A/C compressor clutch relay from the fuse box under the hood and test it.
clutch relay socket and a http://rover.ebay.com/rover/13/0/19/DealFrame/DealFrame.cmp?bm=65&BEFID=96424&aon=%5E1&MerchantID=300086&crawler_id=811181&dealId=AU3e2VNvQrpOGUOAoeMQug%3D%3D&url=http%3A%2F%2Fclickserve.dartsearch.net%2Flink%2Fclick%3Flid%3D92700014999069387%26ds_s_kwgid%3D58700001245061795%26ds_s_inventory_feed_id%3D97700000001002320%26ds_e_product_id%3D99732804%26ci_customer_id%3D1001227%26ci_cse_id%3D1004%26ci_feed_id%3D1004921%26ds_e_product_merchant_id%3D6382239%26ds_e_product_country%3DUS%26ds_e_product_language%3Den%26ds_e_product_channel%3Donline%26ds_url_v%3D2%26ds_dest_url%3Dhttps%3A%2F%2Fwww.kohls.com%2Fproduct%2Fprd-2248176%2Flifetime-48-in-shatterproof-in-ground-basketball-system.jsp%253Fci_mcc%253Dci%2526utm_campaign%253DTEAM%252520SPORTS%2526utm_medium%253DCSE%2526utm_source%253Dshopping%2526CID%253Dshopping17%26sdc_id%3D%7Bsdc_id%7D&linkin_id=8058742&Issdt=170929122607&searchID=p34.cf4a4bfb193467744402&DealName=Lifetime+48-in.+Shatterproof+In-Ground+Basketball+System%2C+Black&dlprc=211.99&AR=3&NG=5&NDP=5&PN=1&ST=7&FPT=DSP&NDS=&NMS=&MRS=&PD=&brnId=14305&IsFtr=0&IsSmart=0&op=&CM=&RR=3&IsLps=0&code=&acode=67&category=&HasLink=&ND=&MN=&GR=&lnkId=&SKU=99732804.
Is there battery voltage? Voltage Good
Yes - Go to step 5.
No - Replace the under-hood fuse box.
5. Connect the #1 and #2 (blue/red wire) terminals of the A/C compressor clutch relay socket with a jumper wire.
Does the A/C compressor clutch click?
Yes - Go to step 6. THIS IS WHERE IT GOT WEIRD, jumped the two terminals, the condenser fan comes on but compressor clutch does not pull in.
No -
* 2001 model: Go to step 14.
* 2002 - 2005 model: Go to step 17.
6. Disconnect the jumper wire.
7. Turn the ignition switch ON (II).
8. Measure the voltage between the #3 (black/yellow wire) terminal of the A/C compressor clutch relay socket and a body ground.
Is there battery voltage? YES VOLTAGE
Yes - Go to step 9.
No - Repair the open in the wire between the #14 fuse in the under-dash fuse box and the A/C compressor clutch relay.
9. Turn the ignition switch OFF.
10. Reinstall the A/C compressor clutch relay.
11. Make sure the A/C is OFF.
12. Turn the ignition switch back ON (II).
13. Using the Back probe set, measure the voltage between the #18 terminal (red wire) of ECM/PCM connector E and a body groundwith the ECM/PCM connectors connected.
Wide side of female terminals
Is there battery voltage? NOT SURE WHERE ECM/PCM is.
Yes - Update the ECM/PCM if the software is out of date (not likely) - or swap it for a known-good one and recheck. If the problem goes away using the replacement ECM/PCM (ECU) .. keep it. NOTE: If you swap ECU's, you'll need to have it reflashed by the dealership or else your car will not run. The only way around this is to get an ECU, keys, and ignition switch from the
No - Repair the open in the wire between the A/C compressor clutch relay and the ECM/PCM.
14. Disconnect the jumper wire.
15. Disconnect the A/C compressor clutch 1-pin connector. MINE IS 3 PIN CONNECTOR
16. Check for continuity between the #1 terminal of the A/C compressor clutch relay socket (blue/red wire) and the A/C compressorclutch 1-pin connector.
Is there continuity?
Yes - Check the A/C compressor clutch clearance, the thermal protector, and the A/C compressor clutch field coil.
No - Repair an open in the wire between the A/C compressor clutch relay and the A/C compressor clutch.
17. Disconnect the jumper wire.
18. Disconnect the A/C compressor clutch 3-pin connector.
19. Check for continuity between the #1 terminal of the A/C compressor clutch relay socket (blue/red wire) and the #2 terminal of the A/C compressor clutch 3-pin connector. (also a blue/red wire)
Is there continuity? YES
Yes - Check the A/C compressor clutch clearance and the A/C compressor clutch field coil.
No - Repair the open in the wire between the A/C compressor clutch relay and the A/C compressor clutch.
Any and all advice is much appreciated and I hope this thread will in the future turn into a reference for people trying to diagnose A/C issues. Thank You
Last edited by hkp; Sep 30, 2017 at 02:52 PM.
Reason: to make it a touch shorter, sometimes people cant handle my length
Re: A/C electrical gurus unite, The dead horse that needs beating
This is for people that want a shorter version, I wanted to leave the long version for people who needed a trouble shooting guide.
1. Check the #1 (20 amp) fuse under the hood, and the #14 (10 amp) fuse under the dash. both good
2. Check the engine coolant temperature, throttle position, and idle speed. (use the HDS PGM-FI data list if possible)
ECT Sensor: 169 - 194 degrees
TPS: About 0.5 volts
RPM: More than 700
Are the coolant temperature, throttle position, and idle speed okay? All Good
3. Remove the A/C compressor clutch relay from the fuse box under the hood and test it.
Is the relay okay? Relay Good
clutch relay socket and a http://rover.ebay.com/rover/13/0/19/DealFrame/DealFrame.cmp?bm=65&BEFID=96424&aon=%5E1&MerchantID=300086&crawler_id=811181&dealId=AU3e2VNvQrpOGUOAoeMQug%3D%3D&url=http%3A%2F%2Fclickserve.dartsearch.net%2Flink%2Fclick%3Flid%3D92700014999069387%26ds_s_kwgid%3D58700001245061795%26ds_s_inventory_feed_id%3D97700000001002320%26ds_e_product_id%3D99732804%26ci_customer_id%3D1001227%26ci_cse_id%3D1004%26ci_feed_id%3D1004921%26ds_e_product_merchant_id%3D6382239%26ds_e_product_country%3DUS%26ds_e_product_language%3Den%26ds_e_product_channel%3Donline%26ds_url_v%3D2%26ds_dest_url%3Dhttps%3A%2F%2Fwww.kohls.com%2Fproduct%2Fprd-2248176%2Flifetime-48-in-shatterproof-in-ground-basketball-system.jsp%253Fci_mcc%253Dci%2526utm_campaign%253DTEAM%252520SPORTS%2526utm_medium%253DCSE%2526utm_source%253Dshopping%2526CID%253Dshopping17%26sdc_id%3D%7Bsdc_id%7D&linkin_id=8058742&Issdt=170929122607&searchID=p34.cf4a4bfb193467744402&DealName=Lifetime+48-in.+Shatterproof+In-Ground+Basketball+System%2C+Black&dlprc=211.99&AR=3&NG=5&NDP=5&PN=1&ST=7&FPT=DSP&NDS=&NMS=&MRS=&PD=&brnId=14305&IsFtr=0&IsSmart=0&op=&CM=&RR=3&IsLps=0&code=&acode=67&category=&HasLink=&ND=&MN=&GR=&lnkId=&SKU=99732804.
Is there battery voltage? Voltage Good
5. Connect the #1 and #2 (blue/red wire) terminals of the A/C compressor clutch relay socket with a jumper wire.
Does the A/C compressor clutch click? THIS IS WHERE IT GOT WEIRD, jumped the two terminals, the condenser fan comes on but compressor clutch does not pull in.
6. Disconnect the jumper wire.
7. Turn the ignition switch ON (II).
8. Measure the voltage between the #3 (black/yellow wire) terminal of the A/C compressor clutch relay socket and a body ground.
Is there battery voltage? YES VOLTAGE
9. Turn the ignition switch OFF.
10. Reinstall the A/C compressor clutch relay.
11. Make sure the A/C is OFF.
12. Turn the ignition switch back ON (II).
13. Using the Back probe set, measure the voltage between the #18 terminal (red wire) of ECM/PCM connector E and a body groundwith the ECM/PCM connectors connected.
Is there battery voltage? NOT SURE WHERE ECM/PCM is.
Yes - Update the ECM/PCM if the software is out of date (not likely) - or swap it for a known-good one and recheck. If the problem goes away using the replacement ECM/PCM (ECU) .. keep it. NOTE: If you swap ECU's, you'll need to have it reflashed by the dealership or else your car will not run. The only way around this is to get an ECU, keys, and ignition switch from the
15. Disconnect the A/C compressor clutch 1-pin connector. MINE IS 3 PIN CONNECTOR
16. Check for continuity between the #1 terminal of the A/C compressor clutch relay socket (blue/red wire) and the A/C compressorclutch 1-pin connector.
Is there continuity?
Yes - Check the A/C compressor clutch clearance, the thermal protector, and the A/C compressor clutch field coil.
No - Repair an open in the wire between the A/C compressor clutch relay and the A/C compressor clutch.
17. Disconnect the jumper wire.
18. Disconnect the A/C compressor clutch 3-pin connector.
19. Check for continuity between the #1 terminal of the A/C compressor clutch relay socket (blue/red wire) and the #2 terminal of the A/C compressor clutch 3-pin connector. (also a blue/red wire)
Ok so anyway......I know how it's supposed to work, so I can skip most troublecausing-charts and simply observe the processes to determine what is present or missing.
Answer this:
(NOTE, the blower fan in the dash MUST RUN or else the control panel disables the AC system)
You turn on the fan and push the AC button on the dash....
You said the compressor does not turn on Do both radiator fans run when you turn the AC on?
If no, ignore the rest of this reply and let me know...we will go on a different path.
If the radiator fans did turn on, that tells me the system has sufficient pressure to allow operation, wiring for the 'AC request' circuit is intact from the HVAC control panel through the pressure switch (and thermal protector on 2002 and newer) and back to the MICU and PCM, PCM "sees" the request and should have turned on both radiator fan relays and compressor clutch relay
so I know I need to focus strictly on the circuits involving the compressor clutch relay, the clutch and coil, and check mechanical issues with the clutch assembly.
I use a long screwdriver to check for the presence of magnetic field at the clutch hub. If the screwdriver is attracted, I then push hard on the hub to see if it engages against the spinning pulley.
If it does, then the air gap is probably far too large.
If it did not engage or field was not present,,,,,then check:
Engine running, AC turned ON:
I remove the compressor clutch relay.
I feel for it to click as I remove it, that indicates its coil was energized with power and ground because the PCM turned it on.
I then check with a simple LOW wattage 12v test light:
I must find 2 powers and 2 grounds in the relay socket. If one ground is missing, that's probably an open field coil. (actually should be somewhere around 3.5-4.5 ohms if you want to check that from the relay socket)
If coil is not open nor excessive resistance, then jumper the 2 larger terminals in the clutch relay socket to supply power to the field coil: Does it click?
If no, then check for excessive air gap
Re: A/C electrical gurus unite, The dead horse that needs beating
Wrong relay, you missed the clutch relay.
I dont know what I was thinking here, I jumped the two wires at the 3 wire plug at the compressor for some dumb reason, that caused the fan to come on, when I jump the relay the clutch pulls in.
NOTE, the blower fan in the dash MUST RUN or else the control panel disables the AC system
Everything on the inside functions as should, ran the a/c DTC and got no codes.
You turn on the fan and push the AC button on the dash....
You said the compressor does not turn on Do both radiator fans run when you turn the AC on?
No, and I checked the low pressure switch on the drier and it is closed.
I also checked the Clutch relay you have labeled as R2, the way I did this was to to pull the relay, if looking at the relay socket from the front of the car, you have to horizontal terminals, and two vertical terminals, the verticals being one and two that you jump to pull in the clutch, the other two, the horizontal closest to firewall has 12v, so I ran a wire from the horizontal socket on the radiator support side, pushed the relay back in, then grounded my jumper wire, the clutch pulled in and the compressor came on, suction pressure around 40psi but head pressure was going up and fan not kicking on so i removed my jumper wire. what sends the ground to the clutch relay to close the relay?
If I'm not making sense, let me know and I will try and grab some pics tomorrow.
If you think a good mechanic is expensive, try hiring a bad one
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Re: A/C electrical gurus unite, The dead horse that needs beating
Do both radiator fans run when you turn the AC on?
No, and I checked the low pressure switch on the drier and it is closed.
Combine this answer with
I jumped the two wires at the 3 wire plug at the compressor for some dumb reason, that caused the fan to come on,
Your thermal protector is probably open circuit. Ohm check that.
At the compressor connector....You could probably jumper the two outer wires together (thermal protector circuit), leave the center wire going to the clutch and the system should then attempt to run on its own.
Re: A/C electrical gurus unite, The dead horse that needs beating
No dice, compressor thermal switch checked out, jumped it on the wiring harness side of the connector incase there was a pin issue in the connector, still no action on compressor clutch.
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 518
Re: A/C electrical gurus unite, The dead horse that needs beating
jumped it on the wiring harness side of the connector incase there was a pin issue in the connector, still no action on compressor clutch.
You jumped the two outer wires, yes?
Earlier you said this made the radiator fans run....so does this still make the fans turn on? (with the HVAC controls set to fan on and ac on)
Do you have a wiring diagram for the AC on this car?
Reasoning: The "AC request" occurs when the HVAC control panel grounds the request line, which mus pass through the closed contacts of the pressure switch, the closed contacts of the thermal protector, to the MICU---- and then the MICU converts that to data and sends it to the PCM.
When the PCM sees the AC request data it then turns on both fan relays and the clutch relay at the same time.
So when you said you got the fans to kick on by jumping the wires from (what I assume to be) the thermal protector, I assumed that part was or is open circuit, interrupting the AC request.
So I would check if the PCM is turning on the clutch relay (supplying ground to the relays coil) at the same time you make the fans kick on.
The relay coil is supplied with 12v+ from (some fuse) and the PCM controls the ground side. PCM output drivers can't handle much load (like less than one amp), so be careful, a short can knock out the PCM.
Also..a GOOD scanner may be able to display the AC request status, the AC clutch relay and fan relay statuses in a live data list. That data is sometimes immensely helpful in troubleshooting.
Re: A/C electrical gurus unite, The dead horse that needs beating
Originally Posted by ezone
You jumped the two outer wires, yes?
Earlier you said this made the radiator fans run....so does this still make the fans turn on? (with the HVAC controls set to fan on and ac on)
I jumped the red wire on the outside to the middle wire, not outside to outside.
I'm starting to wonder if the A/C panel is broke and its not sending the ground, if I check the at thermal switch to ground or the pressure switch, would that let me know if the HVAC control panel is sending that signal?
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 518
Re: A/C electrical gurus unite, The dead horse that needs beating
I jumped the red wire on the outside to the middle wire, not outside to outside.
Oh. ****. No bueno. OK now what happened makes a little more sense.....
The two outer wires are for the protector, the center wire is for the clutch field..
the center pin, IF it was still connected to the compressor clutch field coil, provided sufficient ground to the request line that the PCM turned on the system.....Maybe. I can't tell how you did what you did though.
if I check the at thermal switch to ground or the pressure switch, would that let me know if the HVAC control panel is sending that signal?
UM.... yes.
The "AC request" is simply done by grounding a circuit in the control panel, and that's supposed to make its way around to the MICU......so you should be able to go to any of the items in that circuit (pressure switch, thermal protector) and see if it is grounded.....as long as all items are connected and have continuity. I usually want to backprobe to take readings so I can check with everything connected, in-circuit, live and working.
Real simple AC diagram pic found on goggle search:
In a nutshell, everything between heater control panel and multiplex unit (MICU) is the AC request line and is done with ground.
THE control PANEL is known for failing--unable to supply a ground to the request line. IF this is so, you can pull the panel and provide ground to the blue wire on terminal A4 and the system should run.
The short line that is labeled "communication" is done with data and there is no simple way to test it with a meter.....but it's OK on your car....because you got the fans to kick on.
neither plugs on the heater control panel on terminal 4 have a blue wire, not gonna start grounding things and mess something up, will grab a heater control panel and swap it out. The 01 civic ex 2 door coupe is weird, some parts are vehicle specific and some arent, the multiplex unit was vehicle specific.
Oh Lawd, you found a post from the year I was going through nicotine withdrawals and wanted to kill everyone and everything. Hope I wasn't a total jackazz there.
Re: A/C electrical gurus unite, The dead horse that needs beating
This isn't a case of adjusting the clutch and magnetic coil clearance is it? Mine had to have a shim removed to reduce the clearance on the compressor shaft so that the coil could magnetize the clutch and engage the A/C.
