A/C not working - please advise

[RonJ]

Also, have you checked the heater control panel for trouble codes? If not, here's what you do:

 

[yasen]

The next two tests are:
1) Unplug ECU connectors B and E, turn the key to ON(II), and then measure voltage at ECU connector pins B6 and E18 individually. There should be battery voltage.

2) Replug ECU connectors B and E and then unplug Multiplex Control Unit (MCU) connector E. With the key in ON(II), measure voltage at MCU connector pin E10. There should be 12V (or 5V).

Here is the result of MCU and ECU tests, will do heater control panel test later today.
1. The ECU test: I did unplug B and E connectors from the ECU unit and set key to ON (II) position. Did measure voltage on B6 pin on connector (harness which comec to ECU - green cable) - gave me 12V, did measure the same contact but on ECU plug itself (on the terminal) - gave me 0V.
Did measure voltage on E18 pin on connector (harness which comec to ECU - red cable) - gave me 12V, did measure the same contact but on ECU plug itself (on the terminal)- gave me 0V.

2. Did connect ECU connectors back. Disconnect MCU E connector in underdash fuse/realy box, set car key to ON (II). Did measure voltage on E10 pin on connector (harness which comec to MCU - yellow cable) - gave me 0.05V (I guess it is considered as 0V), did measure the same contact but on MCU plug itself (on the terminal) - gave me 6.53V.

 

[RonJ]

Here is the result of MCU and ECU tests, will do heater control panel test later today.
1. The ECU test: I did unplug B and E connectors from the ECU unit and set key to ON (II) position. Did measure voltage on B6 pin on connector (harness which comec to ECU - green cable) - gave me 12V, did measure the same contact but on ECU plug itself (on the terminal) - gave me 0V.
Did measure voltage on E18 pin on connector (harness which comec to ECU - red cable) - gave me 12V, did measure the same contact but on ECU plug itself (on the terminal)- gave me 0V.

2. Did connect ECU connectors back. Disconnect MCU E connector in underdash fuse/realy box, set car key to ON (II). Did measure voltage on E10 pin on connector (harness which comec to MCU - yellow cable) - gave me 0.05V (I guess it is considered as 0V), did measure the same contact but on MCU plug itself (on the terminal) - gave me 6.53V.

Very good.

The last test is shown in the diagram below. The test is done with no connectors unplugged and the engine running. Back probe terminal F9 in the corresponding MCU connector and ground the other end of the back probe wire. If the A/C does not run, then the problem is probably due to a bad ECU or MCU. Unfortunately, the only way to know is to substitute the current one with a known good one. Junk yards are the place to start.

 

[yasen]

Also, have you checked the heater control panel for trouble codes? If not, here's what you do:

heater control panel test:

I was doing this test and it is not going the way it should be. I am doing steps 1-3 and on step 4 the recirculation indicator goes off as it suppose to do but AC indicator doesn't come on (only rear window defogger in on). Even having this issue I think the test goes forward as it is staring to wlow air from diffrend blowers and after test completed only rear window defogger stays in ON position and no other indication of activity anywhere elese. Anyways, I am going forward with F connector testing, will post my results sometime today.

 

[yasen]

Very good.
The last test is shown in the diagram below. The test is done with no connectors unplugged and the engine running. Back probe terminal F9 in the corresponding MCU connector and ground the other end of the back probe wire. If the A/C does not run, then the problem is probably due to a bad ECU or MCU. Unfortunately, the only way to know is to substitute the current one with a known good one. Junk yards are the place to start.

back probe F connector test:
did start the car and by back probe grounding F9....all works just perfectly...clutch...fans....
Thanks

 

[RonJ]

That's great progress! The ECU and MCU are good.

Now do these tests:

If you measure battery voltage at terminal 4, then start the engine and ground terminal 4 with a jumper wire to the frame under the dash. Does the A/C fan run and the clutch engage?

 

[yasen]

That's great progress! The ECU and MCU are good.

Now do these tests:
If you measure battery voltage at terminal 4, then start the engine and ground terminal 4 with a jumper wire to the frame under the dash. Does the A/C fan run and the clutch engage?

Ok, will be done in the morning. Just to make sure, connector A is in the fuse/relay box and it not the one behind glove box in ECU, right?

 

[RonJ]

Ok, will be done in the morning. Just to make sure, connector A is in the fuse/relay box and it not the one behind glove box in ECU, right?

You are now very close to figuring out the problem, which is likely to be the A/C pressure switch or heater control panel (or wires in between). The next tests will help to pinpoint.

Connector A is located at the rear of the heater control panel. These diagrams should help:

 

[yasen]

You are now very close to figuring out the problem, which is likely to be the A/C pressure switch or heater control panel (or wires in between). The next tests will help to pinpoint.

Connector A is located at the rear of the heater control panel. These diagrams should help:

Will do that....shooot, buy this guy is so far away...have to open everything in my dash.....I will let you know the result and will probably do it tomorrow.
Thanks

 

[RonJ]

Accessing the heater control panel connector is not as bad as you initially think.

 

[Chris.]

all these tests....


did anybody check to see if the system actually had freon in it?

all your tests can come back positive but if there is no freon in the system... then it wont run.

you can jump it to make it run but it wont make it cold... you need to confirm if there is the proper freon pressure in the system before any other troubleshooting is done. once you confirm that there IS freon in there.. then you can continue troubleshooting...

so far ive read this entire thing... and noone has once asked if there is freon in it? and noone has confirmed this either.

 

[yasen]

all these tests....


did anybody check to see if the system actually had freon in it?

all your tests can come back positive but if there is no freon in the system... then it wont run.

you can jump it to make it run but it wont make it cold... you need to confirm if there is the proper freon pressure in the system before any other troubleshooting is done. once you confirm that there IS freon in there.. then you can continue troubleshooting...

so far ive read this entire thing... and noone has once asked if there is freon in it? and noone has confirmed this either.

I know about that. I guess there is no "in-house" was to check for freon in the system. But what I did, I just simply pushed (for a short moment) on H and L pins of frean pipes (pinas a practicly the same as tire ones) and there is a good pressure inside......but there were no liquid coming out. I don't know, may be if I would hold it longer there will be some liquid coming out but i didn't want to hold it even for 1 sec. Thanks for bringing this up. Is there any other way to check?

 

[RonJ]

all these tests....


did anybody check to see if the system actually had freon in it?

all your tests can come back positive but if there is no freon in the system... then it wont run.

you can jump it to make it run but it wont make it cold... you need to confirm if there is the proper freon pressure in the system before any other troubleshooting is done. once you confirm that there IS freon in there.. then you can continue troubleshooting...

so far ive read this entire thing... and noone has once asked if there is freon in it? and noone has confirmed this either.

Chris, did you really read the thread? He jumped the pressure switch connector and the system did not run. See posts 21 and 24.

Yasen, based on your recent results suggesting a problem with either the A/C pressure switch or the heater control panel, you may want to redo the A/C pressure switch connector jumper wire test with the engine running to see whether the A/C system works. If so, the pressure switch may be bad or the refrigerant charge is low, as Chris mentioned.

 

[RonJ]

I know about that. I guess there is no "in-house" was to check for freon in the system. But what I did, I just simply pushed (for a short moment) on H and L pins of frean pipes (pinas a practicly the same as tire ones) and there is a good pressure inside......but there were no liquid coming out. I don't know, may be if I would hold it longer there will be some liquid coming out but i didn't want to hold it even for 1 sec. Thanks for bringing this up. Is there any other way to check?

Refrigerant liquid should not come out of the valves, only gas.

 

[Chris.]

sorry i did not see that he jumped the switch.. i only saw that he tested it.

if theres freon in the system like you said... it should be coming out of that valve at a pretty good rate if the charge is decent.. and the gas will instantaneously turn white when it hits air... it will freeze your finger if thats what you used.

there is a way to check for pressure... they sell a set of guages at the parts store that you can hookup and check... they also sell what looks like a tire pressure checker but has a different tip on it. its a little cheaper but still tells you roughly what you need to know..

if theres freon... and you say the pressure switch is working properly... then it has to be in the actual switches in the dash.

 

[RonJ]

sorry i did not see that he jumped the switch.. i only saw that he tested it.

Still, given that the OP's troubleshooting now points to either the pressure switch or heater control panel, I think the test of jumping the pressure switch connector should be done again.

 

[yasen]

Still, given that the OP's troubleshooting now points to either the pressure switch or heater control panel, I think the test of jumping the pressure switch connector should be done again.

Not a problem, I will do the pressure switch test today again and will do my best to complete the heater control panel connector A test.
Thanks

 

[yasen]

Still, given that the OP's troubleshooting now points to either the pressure switch or heater control panel, I think the test of jumping the pressure switch connector should be done again.

Hi, I've done the pressure switch test again. I did unplug switch pressure terminal, started up the car and jumped blue/white cable to ground - nothing is happening.....see picture, just to avoid misunderstanding. I did trace the red cable again (i did it before once) from the same swtitch it goes to thermal protector switch. So, I jumped this red wire from pressure switch connector to the ground....fans and compressor clutch started.

I going to proceed with heater control panel test right now.

BTW, I bought this car used...may be these two cables on pressure switch are switched over by somebody before I got it?

 

[RonJ]

I did unplug switch pressure terminal, started up the car and jumped blue/white cable to ground - nothing is happening.....see picture, just to avoid misunderstanding.

I did trace the red cable again (i did it before once) from the same swtitch it goes to thermal protector switch. So, I jumped this red wire from pressure switch connector to the ground....fans and compressor clutch started.

BTW, I bought this car used...may be these two cables on pressure switch are switched over by somebody before I got it?

Hmmm...the pressure switch connector should have a Blu/Wht wire and a Blu wire. So it seems that the Red wire is functionally equivalent to the Blu/Wht wire. But what do you mean that the Red wire goes to the thermal protector switch? That is not right. The thermal protector is on the A/C compressor. Please post a picture. Are you sure the connector in your picture is for the A/C pressure switch?

Finally, if you jump the Red wire to the Blu/Wht wire in the unplugged pressure switch connector, does the A/C run when the engine is running and the A/C button is turned on?

 

[yasen]

Hi Just a small correction, there are two wires on the pressure switch, the one blue with white strips and another red with white strips.
Here is a pictire of my pressure switch:

and here is a picture of my thermal protector connector ......which sits on top of compressor clutch. The red wire with white strips goes from pressure switch to thermal protector switch.

And yes, it is all working if I jump both wires together on the pressure switch connector.