a/c question
Thread Starter
Burning Brakes
Joined: Jun 2004
Posts: 752
Likes: 0
From: richardson tx
a/c question
`90 model with electronic climate control. tryed to get the a/c clutch to engage today but nothing, jumped the pressure switch still nothing. checked the pressure plugs, temp plug and clutch plug with a test light. not getting fire to any of them. pulled ccm codes there were none except c12 which tells you that the system is operational. pulled the a/c clutch relay and jumped the wires at the harness all four and the clutch comes on. so i replaced the relay now nothing again. what do you think?
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 41
From: Baltimore, MD USA
You probably have a code 09 set in the AC programmer.
Turn the ignition to run.
To enter diag. mode hold the Fan up and Fan down button at the same time for at least 5 seconds.
The AC Control Head LCD will display any fault codes.
09 indicates low refrigerant. 00 indicates no faults.
If you do see 09 you need to find and fix the leak. After that clear the fault code by disconnecting the negative battery cable.
Turn the ignition to run.
To enter diag. mode hold the Fan up and Fan down button at the same time for at least 5 seconds.
The AC Control Head LCD will display any fault codes.
09 indicates low refrigerant. 00 indicates no faults.
If you do see 09 you need to find and fix the leak. After that clear the fault code by disconnecting the negative battery cable.
Last edited by Hooked on Vettes; Jul 16, 2006 at 09:40 PM.
Thread Starter
Burning Brakes
Joined: Jun 2004
Posts: 752
Likes: 0
From: richardson tx
Originally Posted by Hooked on Vettes
You probably have a code 09 set in the AC programmer.
Turn the ignition to run.
To enter diag. mode hold the Fan up and Fan down button at the same time for at least 5 seconds.
The AC Control Head LCD will display any fault codes.
09 indicates low refrigerant. 00 indicates no faults.
If you do see 09 you need to find and fix the leak. After that clear the fault code by disconnecting the negative battery cable.
Turn the ignition to run.
To enter diag. mode hold the Fan up and Fan down button at the same time for at least 5 seconds.
The AC Control Head LCD will display any fault codes.
09 indicates low refrigerant. 00 indicates no faults.
If you do see 09 you need to find and fix the leak. After that clear the fault code by disconnecting the negative battery cable.
Thread Starter
Burning Brakes
Joined: Jun 2004
Posts: 752
Likes: 0
From: richardson tx
since iv converted to carb i did have to jump the cts as its part of the a/c request loop. i think the tps is as well. maybe i should hook up an old tps sensor. dont think i can jump the connector as it has 3 prongs.
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 41
From: Baltimore, MD USA
On a 90 the programmer sends the ECM an AC request.
The ECM grounds the Gray wire at the AC Clutch Relay.
The relay closes and 12 volts from the Light Green wire goes thru the AC High Pressure Cut out switch which should be closed. 12 volts passes out of the switch on the Black wire which goes to the Pressure Cycling switch which should be closed as long as the refrigerant pressure is at least 47 psi. The 12 volts then goes to the compressor clutch which engages the compressor.
AC request>ECM AC enable>grounds AC clutch relay.
12 volts from AC relay>AC High Pressure Switch>Pressure Cycling Switch>AC compressor Clutch.
The 90 doesn't use a 3 wire pressure sensor.
The ECM does cut off the AC if it sees WOT.
The ECM grounds the Gray wire at the AC Clutch Relay.
The relay closes and 12 volts from the Light Green wire goes thru the AC High Pressure Cut out switch which should be closed. 12 volts passes out of the switch on the Black wire which goes to the Pressure Cycling switch which should be closed as long as the refrigerant pressure is at least 47 psi. The 12 volts then goes to the compressor clutch which engages the compressor.
AC request>ECM AC enable>grounds AC clutch relay.
12 volts from AC relay>AC High Pressure Switch>Pressure Cycling Switch>AC compressor Clutch.
The 90 doesn't use a 3 wire pressure sensor.
The ECM does cut off the AC if it sees WOT.
Thread Starter
Burning Brakes
Joined: Jun 2004
Posts: 752
Likes: 0
From: richardson tx
Originally Posted by Hooked on Vettes
On a 90 the programmer sends the ECM an AC request.
The ECM grounds the Gray wire at the AC Clutch Relay.
The relay closes and 12 volts from the Light Green wire goes thru the AC High Pressure Cut out switch which should be closed. 12 volts passes out of the switch on the Black wire which goes to the Pressure Cycling switch which should be closed as long as the refrigerant pressure is at least 47 psi. The 12 volts then goes to the compressor clutch which engages the compressor.
AC request>ECM AC enable>grounds AC clutch relay.
12 volts from AC relay>AC High Pressure Switch>Pressure Cycling Switch>AC compressor Clutch.
The 90 doesn't use a 3 wire pressure sensor.
The ECM does cut off the AC if it sees WOT.
The ECM grounds the Gray wire at the AC Clutch Relay.
The relay closes and 12 volts from the Light Green wire goes thru the AC High Pressure Cut out switch which should be closed. 12 volts passes out of the switch on the Black wire which goes to the Pressure Cycling switch which should be closed as long as the refrigerant pressure is at least 47 psi. The 12 volts then goes to the compressor clutch which engages the compressor.
AC request>ECM AC enable>grounds AC clutch relay.
12 volts from AC relay>AC High Pressure Switch>Pressure Cycling Switch>AC compressor Clutch.
The 90 doesn't use a 3 wire pressure sensor.
The ECM does cut off the AC if it sees WOT.
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Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 41
From: Baltimore, MD USA
I have no idea what you've disconnected on the ECM.
You can tell if the AC Programmer is requesting AC by using a volt meter and verify there is 12 volts on the ECM Red connector pin 15 which should be a Gray/Red wire.
Should be 12 volts when AC is being requested by the HVAC Programmer.
The ECM then decides if it should ground the gray wire on the AC Relay. (AC Enable)
Note: When the ECM does provide the AC Enable, the ECM also raises the engine rpm to compensate for the additional engine load by using the IAC.
If the ECM doesn't ground the relay and you don't have a code 09 (Low Freon), the only thing I can think of is it thinks the TPS is at WOT.
I'm guessing the code to disable the ECM from grounding the AC Relay when the TPS is at WOT is in the Eprom firmware.
I'm surprised the ECM is not throwing a code 22 which is TPS voltage low if you don't have any TPS hooked up.
You can tell if the AC Programmer is requesting AC by using a volt meter and verify there is 12 volts on the ECM Red connector pin 15 which should be a Gray/Red wire.
Should be 12 volts when AC is being requested by the HVAC Programmer.
The ECM then decides if it should ground the gray wire on the AC Relay. (AC Enable)
Note: When the ECM does provide the AC Enable, the ECM also raises the engine rpm to compensate for the additional engine load by using the IAC.
If the ECM doesn't ground the relay and you don't have a code 09 (Low Freon), the only thing I can think of is it thinks the TPS is at WOT.
I'm guessing the code to disable the ECM from grounding the AC Relay when the TPS is at WOT is in the Eprom firmware.
I'm surprised the ECM is not throwing a code 22 which is TPS voltage low if you don't have any TPS hooked up.
Last edited by Hooked on Vettes; Jul 17, 2006 at 01:07 AM.
Thread Starter
Burning Brakes
Joined: Jun 2004
Posts: 752
Likes: 0
From: richardson tx
Originally Posted by Hooked on Vettes
I have no idea what you've disconnected on the ECM.
You can tell if the AC Programmer is requesting AC by using a volt meter and verify there is 12 volts on the ECM Red connector pin 15 which should be a Gray/Red wire.
Should be 12 volts when AC is being requested by the HVAC Programmer.
The ECM then decides if it should ground the gray wire on the AC Relay. (AC Enable)
Note: When the ECM does provide the AC Enable, the ECM also raises the engine rpm to compensate for the additional engine load by using the IAC.
If the ECM doesn't ground the relay and you don't have a code 09 (Low Freon), the only thing I can think of is it thinks the TPS is at WOT.
I'm guessing the code to disable the ECM from grounding the AC Relay when the TPS is at WOT is in the Eprom firmware.
I'm surprised the ECM is not throwing a code 22 which is TPS voltage low if you don't have any TPS hooked up.
You can tell if the AC Programmer is requesting AC by using a volt meter and verify there is 12 volts on the ECM Red connector pin 15 which should be a Gray/Red wire.
Should be 12 volts when AC is being requested by the HVAC Programmer.
The ECM then decides if it should ground the gray wire on the AC Relay. (AC Enable)
Note: When the ECM does provide the AC Enable, the ECM also raises the engine rpm to compensate for the additional engine load by using the IAC.
If the ECM doesn't ground the relay and you don't have a code 09 (Low Freon), the only thing I can think of is it thinks the TPS is at WOT.
I'm guessing the code to disable the ECM from grounding the AC Relay when the TPS is at WOT is in the Eprom firmware.
I'm surprised the ECM is not throwing a code 22 which is TPS voltage low if you don't have any TPS hooked up.
Thread Starter
Burning Brakes
Joined: Jun 2004
Posts: 752
Likes: 0
From: richardson tx
pulled up modules 4.0, 4.1 and 4.7 for ecm codes. they all flat lined after each. meaning end of file with no codes set not even history ones. the check engine light does come one with the key on so i know there is not a serial link issue.
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 41
From: Baltimore, MD USA
To check for codes.
Short Pin A which is Ground to Pin G.
Using this method the CCM is communicating with the different modules
Turn the ignition to run (don't start the engine).
Let the display cycle. Don't press any buttons.
The speedometer LCD should show the following.
I think you'll see C12 then
1.1 and then any CCM errors
4.1 and then any ECM errors
7.1 and you should see ERR
----- means no error codes.
If you're not seeing module 4 which is the ECM, you should see ERR.
To see if the ECM is working, short pin A to B and turn the ignition on.
Should see the Service Engine Soon blink 12 three times, any codes 3 times then 12 again 3 times. If the Service Engine Soon doesn't work, the bulb is burned out or the ECM is not working which is why the AC is not working.
Short Pin A which is Ground to Pin G.
Using this method the CCM is communicating with the different modules
Turn the ignition to run (don't start the engine).
Let the display cycle. Don't press any buttons.
The speedometer LCD should show the following.
I think you'll see C12 then
1.1 and then any CCM errors
4.1 and then any ECM errors
7.1 and you should see ERR
----- means no error codes.
If you're not seeing module 4 which is the ECM, you should see ERR.
To see if the ECM is working, short pin A to B and turn the ignition on.
Should see the Service Engine Soon blink 12 three times, any codes 3 times then 12 again 3 times. If the Service Engine Soon doesn't work, the bulb is burned out or the ECM is not working which is why the AC is not working.
Last edited by Hooked on Vettes; Jul 17, 2006 at 02:13 AM.
Thread Starter
Burning Brakes
Joined: Jun 2004
Posts: 752
Likes: 0
From: richardson tx
Originally Posted by Hooked on Vettes
To check for codes.
Short Pin A which is Ground to Pin G.
Turn the ignition to run (don't start the engine).
The speedometer LCD should show the follwing.
I think you'll see C12 then
1.1 and then any CCM errors
4.1 and then any ECM errors
7.1 and you should see ERR
----- means no error codes.
If your not seeing module 4 which is the ECM, you should see ERR.
Short Pin A which is Ground to Pin G.
Turn the ignition to run (don't start the engine).
The speedometer LCD should show the follwing.
I think you'll see C12 then
1.1 and then any CCM errors
4.1 and then any ECM errors
7.1 and you should see ERR
----- means no error codes.
If your not seeing module 4 which is the ECM, you should see ERR.
Thread Starter
Burning Brakes
Joined: Jun 2004
Posts: 752
Likes: 0
From: richardson tx
Originally Posted by Hooked on Vettes
Can you short A to B and the Service Engine Soon light blinks 12?
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 41
From: Baltimore, MD USA
Sounds right should be flash pause flash flash which is
12.
I don't know what sensors you still have hooked up to the ECM but it appears the ECM doesn't set many of the error codes unless the engine is running.
The only way the ECM knows the engine is running is by the signal from the control module inside the distributor.
Is that hooked up to the ECM?
I'm guessing the ECM will not enable the AC clutch unless the engine is running.
12.
I don't know what sensors you still have hooked up to the ECM but it appears the ECM doesn't set many of the error codes unless the engine is running.
The only way the ECM knows the engine is running is by the signal from the control module inside the distributor.
Is that hooked up to the ECM?
I'm guessing the ECM will not enable the AC clutch unless the engine is running.
Thread Starter
Burning Brakes
Joined: Jun 2004
Posts: 752
Likes: 0
From: richardson tx
Originally Posted by Hooked on Vettes
Sounds right should be flash pause flash flash which is
12.
I don't know what sensors you still have hooked up to the ECM but it appears the ECM doesn't set many of the error codes unless the engine is running.
The only way the ECM knows the engine is running is by the signal from the control module inside the distributor.
Is that hooked up to the ECM?
I'm guessing the ECM will not enable the AC clutch unless the engine is running.
12.
I don't know what sensors you still have hooked up to the ECM but it appears the ECM doesn't set many of the error codes unless the engine is running.
The only way the ECM knows the engine is running is by the signal from the control module inside the distributor.
Is that hooked up to the ECM?
I'm guessing the ECM will not enable the AC clutch unless the engine is running.
Is that hooked up to the ECM?
not exactly. im using a msd billet 2 wire hei distributor. hot and ground ( and tach ) . also during my travels iv only been testing for the a/c while the car is running. old a/c clutch relay nothing, new relay nothing, no relay and harness jumped at the relay connector the clutch kicks on and cycles.
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 41
From: Baltimore, MD USA
If you just want to get the AC to work, reinstall the AC
Clutch Relay. Use a switch with one end to ground and one end to the Gray wire at the AC Relay. When you turn the switch on, the relay will close and the Compressor Clutch will engage.
This defeats the purpose of AC Auto Climate Control but at least you'll have AC.
Clutch Relay. Use a switch with one end to ground and one end to the Gray wire at the AC Relay. When you turn the switch on, the relay will close and the Compressor Clutch will engage.
This defeats the purpose of AC Auto Climate Control but at least you'll have AC.