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Discussion Starter · #1 ·
The first warm day of spring I noticed that my A/C doesn't work. Thinking now that expensive Helms manual will finally pay off, I go to page 21-67 and try to retrieve DTC's per the proceedure. It doesn't appear to work so I try to read the sensors via the proceedure on the next page. This clearly doesn't work. What am I doing wrong?

My van is a 2003 EX and the dealer just replaced the timing belt for me. Suppose they let the freon out of my system in the process?
Thanks,
JB
 

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Check the #59 (7.5 A), #58 (30 A), #56 (40 A) and the #54 (40 A) fuses in the Under-Hood Fuse/Relay Box and the #3 (7.5 A) in the Driver's Under-Dash Fuse/Relay Box.

To retrieve HVAC DTCs:

1. Turn the ignition switch to ON (II).

2. Turn the fan switch OFF.

3. Press the recirculation control button to select Recirculation (indicator comes on).

4. Press and hold the recirculation control button top select Fresh (indicator goes off). Continue to hold the button until the recirculation indicator comes on for 2 seconds, and then goes off.

If the system is OK, the recirculation indicator stays off.

If any trouble is found, the recirculation indicator blinks the diagnostic trouble code (DTC) to indicate faulty component or circuit.

1 blink = a problem in the air mix control motor circuit.
2 blinks = a problem in the mode control motor circuit.
3 blinks = a problem in the evaporator temperature sensor circuit.

5. Turn the ignition switch to OFF to cancel the self-diagnosis function. Check for additional DTCs after repair work has been done.

Check the #59 (7.5 A), #58 (30 A), #56 (40 A) and the #54 (40 A) fuses in the Under-Hood Fuse/Relay Box and the #3 (7.5 A) in the Driver's Under-Dash Fuse/Relay Box.
 

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A/C Problems

Other posts have outlined the procedure for determining if your compressor is actually coming on (you need a helper to turn on the A/C in the car while you listen under the hood for a click).

In my experience (we have a 2000 EX with A/C on the blink), it is likely a leak somewhere that causes the pressure in the system to drop and the pressure switch detects this and does not allow the compressor to come on (so that it is not ruined by pumping without refrigerant and lubricant).

All of which is to say, the garage just found our leak in the two hard lines that seem to go from the fire wall back inside the subframe and feed the rear A/C unit.

Very expensive to change because the hard lines are buried and require dropping the front subframe. So much for superior engineering. In my view, they should route these lines in an accessible fashion and make them out of stainless tubing - given their exposure to the elements and the pressure they must contain.

Anyway, you will likely need to have the system pressurized with fluorescent dye to find the leak and apparently the lines to the rear unit are a likely culprit. Good luck.
 

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Discussion Starter · #5 ·
Thanks for the help fellows. The fuses are good and I can hear the compressor clutch energize when someone inside turns the A/C on and off.

The procedure outlined above I believe is for the control with manual fan control. Mine has automatic fan control and in the service manual it is called "Climate Control". It is supposed to offer 14 diag codes by turning on certain segments in the temperature display LCD. Entering diag is a similar process:
1. turn ignition switch on (II)
2. Press AUTO button then press OFF button. Continue to hold both buttons down for 1 minute.

This control is also supposed to display sensor inputs. To enter that function:
1. turn ignition switch off
2. press and hold both the AUTO and RECIRC buttons, then start the engine
3. After engine starts, release the buttons. The climate control display will flash the sensor number and then the value for that sensor.
4. To advance to the next sensor press the rear window defogger button.

This function doesn't work as advertised either. It is supposed to indicate the position of the mode motor and that would be pretty useful I think.

Still sweating.....
 

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I have the exact same issue. I can't get climate control system to report DTC (which may be OK) or sensor outputs (which should be displayed regardless of fault or not).

The symptoms I have:
* Freon evacuate and refill to spec pressor: DONE by repair shop
* Basic electrical diagnostics done by repair shop. Nothing found.
* Blower fan only works on Hi an Lo temperature dial positions.
* When on "Lo" setting, compressor would engage for a couple of seconds (after engine is turned on) and then disengage.

Absent of sensor outputs leads me to believe that I have a fault climate control unit. Is my logic correct?

Can anyone with a working climate control system try to get sensor readings out? Can it be done on a working system at all?

Thanks
 

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OK. The sensor test works using following steps! (Manual has incorrect steps).

* Turn off ignition
* Press Auto and Mode button together and start the engine.
* Release both buttons
* Use rear defogger to cycle through sensor readings.

My readings:
* Mode Motor Position: Vent
* In-car temperature: 38 C
* Ambient temperature: 36 C
* Solar radiation Sensor value: 0
* Engine coolant temperature: 71 C
* Evaporator outlet air temperature: 39 C
* Air mix opening: 16%
* Vent temperature air out: 25 C

What seems to be out of whack is "vent temperature air out". Is having only one of this sensor bad can cause the symptoms I described?

Repair shop says it's a wiring problem and they want to work by an hour without any time estimate! I am going to fix it myself or never fix it.

Thanks.
 

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Opened the transistor assembly and checked the thermal cut off. It is blown as expected. I know Radio Shake has 250v, 10 A thermal fuses for various temperatures so I will try the shack tomorrow morning. I had to replace a thermal fuse on my blender once and the shack had it.

Since the climate control PCM module has a 12V comparator off of this thermal cut off connection, PCM shuts down everything (My theory based on the circuit diagram), which makes sense as a design principal. If transistor is about to be blown due to high heat => blower won't run => AC is useless at this point => shut off compressor => repair shop scratching their head!! and wanting to charge me hourly labour to trace the wires?

Honda should have had a DTC for this case, easy to implement. BTW I am an electrical engineer so wanted to through my theory out for Honda to use.
 

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I checked that thermal cut off was blown so I replaced the thermal cut off using part from Fry's. They have a 117C thermal cutoff for $1. After that the blower came on with full speed by just turning the keys to ON position. Turning on/off the climate control made no difference in the blower speed. Then I followed the power transistor tests described on page 21-120 of the service manual. That indicated that the transistor was also dead. At that point it was faster for me to drive to dealership and buy the whole transistor assembly for $60. Problem solved.

1. Disconnect the 5P connector from the power
transistor.
2. Measure the resistance between the No. 1 and
No. 4 terminals of the power transistor. It should be
approximately 1.4 1.5 k .
• If the resistance is within the specifications, go to
step 3.
• If the resistance is not within the specifications,
replace the power transistor.
3. Carefully release the lock tab on the No. 3 terminal
(ORN/BLK) (A) in the 5P connector, then remove the
terminal and insulate it from body ground.
4. Connect a 1.2 3.4 W bulb (B) between the No. 3
and the No. 4 cavity on the 5P connector.
5. Reconnect the 5P connector to the power transistor.
6. Turn the ignition switch ON (II), and check that the
blower motor runs.
• If the blower motor does not run, replace the
power transistor.
• If the blower motor runs, replace the climate
control unit.


By the way, after the fuse replacement, DTC test worked and showed a DTC N for problem with blower circuit. I took a short cut described above without going into 47 steps diagnostics of blower circuit starting on page 21-99.

Thanks
 

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By the way, in my transistor test, step 2 passed. Step 6 did not run blower. Steps 3-5 were handful! I had to dig out my tool box for bulb, wires, tab release, etc.

Essentially steps 3-5 is a way to fake a transistor so the climate control module can do it's job. If blower stays on at full speed (with keys in ON, engine off) even with this dummy transistor then the control module is gone bad.

Thanks.
 

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Essentially steps 3-5 is a way to fake a transistor so the climate control module can do it's job. If blower stays on at full speed (with keys in ON, engine off) even with this dummy transistor then the control module is gone bad.

Thanks.
I am dealing with this issue right now with my 2000 EX and I would like to correct pjigar's stmt above. The Climate Control module controls the power transistor on/off. So steps 3-5 are essentially providing a "fake" control module system voltage to the transistor to see if the power transistor will turn on and allow the circuit to complete. If the blower fan works, the control system is faulty. If the fan does not work, the transistor is bad. I will update this post later after my completing my diagnosis.
 

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Update - I failed test 1-2 as I measured 1.6 megaohms vs. 1.4-1.5 Kohms. yes I double checked the resistance. That test is testing the thermal cutoff resistor, which often is just open, but in my case is just as well open as 1.2Mohms is very high resistance. That kind of makes sense since my fan blower sometimes worked, sometimes didn't. it all started one very hot day when it was very hot inside the car. Then it started working a few days later, then stopped again. So the resistor didn't go open, it just increased resistance until it was out of spec.

So I will be placing the order for the thermal cutoff P10920-ND. Kind of stupid to buy something for $.75 so maybe I will buy two. Will update later
 

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So just for the record, I will update my situation. I received the thermal cutoff, but before I replaced it I checked the existing resistance and found them to be in tolerance. I might have been checking the wrong pins as it was supposed to be pins 1 & 4 and I might have been testing 3 & 4. Anyway I replaced it since I had a new one and still had issues. At some point, before or after the change I lost AC in the rear, which I was using to keep cool. The fan clutch was not kicking in and causing the ac to work. It didn't matter if the resistor was connected or not. I determined that the transistor had to be bad and purchased a complete replacement unit on ebay for $20. Received it today and everything is fine. I believe the Climate Control computer gets messed up and can produce weird results if the resistor/transistor unit is bad. Replace this as one of the first items. The unit I got looks identical to other OEM pics, but it just doesn't have Denso stamped anyplace on it... So replace that unit early on if you have issues. There is an NPN transistor in the unit along with the thermal cutoff and a small resistor and capacitor. They may not "fail" but just drift in their specs which can cause weird symptoms.
 

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Since the climate control PCM module has a 12V comparator off of this thermal cut off connection, PCM shuts down everything (My theory based on the circuit diagram), which makes sense as a design principal. If transistor is about to be blown due to high heat => blower won't run => AC is useless at this point => shut off compressor => repair shop scratching their head!! and wanting to charge me hourly labour to trace the wires?

Honda should have had a DTC for this case, easy to implement. BTW I am an electrical engineer so wanted to through my theory out for Honda to use.
pjigar.. if you are still out there, please check your private messages. I'd like to discuss this theory on the comparator. I think you are onto something.
 

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I'm brand new on this forum. I wanted to add my two cents.

We just purchased our used 2000 ody and the ac didn't work. I recharged it and it began running but had no pressure. Then u found a great video on YouTube about the filter. Sure enough the cabin filter was filthy and plugged with dog hair.

Ac works great now!!!
 
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