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George H.
George H., ASE Certified Technician
Category: Honda
Satisfied Customers: 18393
Experience:  ASE Master Tech 15+ years
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Civic Si: I have an A/C-heater issue that I thought I had fixed

Customer Question

I have an A/C-heater issue that I thought I had fixed a few months ago. Issue started with the air (fan) stopped blowing air. I scoured the Honda forums online and they more or less said it could be the HVAC resistor (among other things). I replaced the HVAC resistor with a new one and saw the problem solved - for 1 day. I attempted to fix the problem again (after a few weeks). I started by replacing the air filters. I checked the fuses under the hood and all are working. I looked at the fuses under the dash and didn't see any that needed replacing. I then used a multi-meter to see if the plug for the blower motor is supplying the motor with power. Multi-meter showed 12 volts coming through. Just to make sure the blower motor wasn't the problem, I removed it and attached it to a 12-volt battery in my garage. Blower motor spun without problems. I re-installed the blower motor and connected its plug. I started the engine and the a/c worked perfectly. Couldn't figure it out. A/C worked fine for about 3 weeks or so and then, one day, nothing. That was about a month ago. I attempted to fix it again before contacting this site; I went through all the previous checkpoints and came up a negative. I don't want to spend any more money on parts until I'm pretty sure what's happening.
Submitted: 1 year ago.
Category: Honda
Expert:  George H. replied 1 year ago.
Hello I will help you with your question,
Please make all measurements with the connectors plugged in and the engine running with the blower on high.
Use a straight pin to slide along the wire and make contact inside the connector to measure from.
Do you have 12 volts at the blue/black stripe wire at the transistor?
If you do is there a changing voltage on the blue/yellow stripe wire when you change the blower speed?
Let me know how I can help
Customer: replied 1 year ago.
I used the red lead wire from the multi-meter to test the voltage on the blue/black (actually green/black) wire. I didn't attach the black lead from multi-meter to anything. I got no voltage reading on the green/black wire. I then attached red lead wire to the blue/yellow stripe wire and also got no reading. Engine was on the fan speed was on high.
Expert:  George H. replied 1 year ago.
You may be blue/green colorblind, the wire is blue just as the one next to it is blue/white, no big deal I just wanted you to know. You need to put the black lead of the meter to a clean metal part of the body. The ground bolt in the kick area in front of the door opening is a good ground. Let me know if you measure the voltage at the blue/black wire with the meter black connected to ground. Thank you
Customer: replied 1 year ago.
Okay. Here are the 4 wire color schemes: black, black/green, green/yellow, and blue/red. I'm not colorblind. I attached the red lead to the black/green wire and the ground to where you requested. I couldn't get a read at all when the multi-meter was on 200V. I switched the meter to 20V and the b/g wire showed a read of 1.55 when fan selector was on full.
Expert:  George H. replied 1 year ago.
OK, on a 2002 si you can see the colors at the link below
https://dl.dropboxusercontent.com/u/26725849/f.pdf
Copy and pate the link into a new browser tab and let me know where you have power with everything plugged in.
Thanks
Customer: replied 1 year ago.
Terminal 1 has the same results as previously posted.
Expert:  George H. replied 1 year ago.
I am sorry but I am unable to speak on the phone. If you find the 12 volts at #1 in the diagram that is the blue/white wire to the motor. Can you measure at the transistor and see if you have that same 12 volts on the blue/black stripe wire?
Customer: replied 1 year ago.
None of the 4 connections on the transistor gave me 12 volts. The maximum voltage I found was 1.55V.
Expert:  George H. replied 1 year ago.
OK lets back up to the fuse,
In the underhood fuse block the 40 amp #12 supplies the blower, under the dash the #14 10 amp fuse is the other half that brings power to the transistor.
Let me know what you find when you check those fuses.
Thank you
]
Customer: replied 1 year ago.
Yes. Both the 40 amp under the hood is working. I switched the power window fuse (also 40 amp) to check. Under the dash, I don't have any bad fuses. The #14 10 amp fuse is also good.
Expert:  George H. replied 1 year ago.
OK then you should have 12 volts at the transistor. Check the diagram. You can pull the blower motor rely from the underhood fuse block and swap it with another. It may be the problem if you have power at the fuse but not at the transistor. Let me know how I can help Thank you
Customer: replied 1 year ago.
I've swapped all the 40 amp fuses in the under hood fuse box. I know they are all working. Is it possible there is a short in the wiring?
Expert:  George H. replied 1 year ago.
It is the relay I suggested swapping not the fuses. Anything is possible at this point, if you can tell me that you have 12 volts to the relay we can move on, if you have 12 volts to the blue/white wire at the blower motor
Customer: replied 1 year ago.
Yep. My apology. I misread your last directive. The blower motor relay is one of the black rectangular pieces, correct?
Expert:  George H. replied 1 year ago.
Yes, do you need a diagram to locate it?
Customer: replied 1 year ago.
Not at all. Here is how I checked that. I noticed that the front left headlight has the same piece. I switched out the left headlight with the blower motor relay. I actually switched all the black rectangular pieces with the left headlight and they all appear to be in working order (the headlight came on).
Expert:  George H. replied 1 year ago.
As long as they are the same that will work. You have power to the relay contacts? Two Of them? Key on blower on high?
Customer: replied 1 year ago.
Gimme about 5-10 minutes. I'm going back out to check the voltage on the transistor (located behind the glove compartment). I'm a little confused as to how I can get 12V at the blower motor power plug and not 12V at the transistor.
Expert:  George H. replied 1 year ago.
No problem, I am here for another hour.
Check the diagram, the power from the fuse through the relay comes to the motor and the motor is one piece of wire so if there is no ground from the transistor to run the motor you will have 12 volts at the transistor.
Let me know what you measure
Thank you
Customer: replied 1 year ago.
Alright. I looked again at the diagram after testing the transistor. I have no voltage on terminals 1, 2, or 4. Car is running, fan speed is full blast and I can't get any voltage on those terminals. I kept the car running, fan speed full blast and unplugged the blower motor and tested the terminal on it and got a 14V reading.
Customer: replied 1 year ago.
If it's the power transistor, I replaced that a couple months ago. Is there something else that may be causing that part to break?
Expert:  George H. replied 1 year ago.
So you have no voltage at the transistor, do you have voltage at two of the relay pin sockets?
Customer: replied 1 year ago.
I don't see on the diagram where the relay pin sockets are. I don't have a definitive answer for you.
Expert:  George H. replied 1 year ago.
https://dl.dropboxusercontent.com/u/26725849/blow.pdf
Try that link. It will show the relay and the transistor connections
Customer: replied 1 year ago.
I guess I'm not understanding the diagram like I should. Where are the relay pin sockets? Under the hood next to the fuse box? I can't find it.
Expert:  George H. replied 1 year ago.
The relay is in the underhood fuse block marked AC clutch as shown if you click here Pull the relay and check the sockets for the relay pins under it for voltage. Look on the relay, the pin numbers should be printed on it. Let me know what you find and how I can help Thank you
Customer: replied 1 year ago.
Okay. I just got a chance to review everything we talked about yesterday. The new diagram showing the underhood fuse box is very helpful. Earlier in our troubleshooting you suggested the blower motor relay might be the problem if I have power at the fuse but not the transistor. Unfortunately, I will have to go purchase the relay as I don't have a spare.
Expert:  George H. replied 1 year ago.
You can bypass the relay with a paperclip and if you then have power to the transistor you could check the relay control.
Do you have 12 volts to two of the relay pin sockets with the key on and the blower on high?
Customer: replied 1 year ago.
Engine on, blower motor on high, I have top left socket reads -14.0V (negative). The bottom left socket reads -00.2V (negative). Top and bottom right sockets give readings of 00.0V.
Expert:  George H. replied 1 year ago.
Ok so you only have one of the 4 with voltage, the negative reading is due to having the meter leads reversed. No problem there. You want two of the relay pin sockets to have 12 volts, so check the fuses for the blower which is the 40 amp #12 in the underhood box and the 10 amp red #14 in the under dash fuse block. Check that you have battery voltage at both fuse sockets and both testpoints on the back of the 10 amp fuse with it installed in the fuse block. Thanks
Customer: replied 1 year ago.
Engine on, blower on full; #12 under hood has no voltage. #14 has 13.4V. Now I'm not an electrician. I tested the 40 amp by touching red lead to one socket and the black to the other. Then switched it. Nothing. The 10 amp under dash I tested the same way. Is this correct?
Customer: replied 1 year ago.
My check engine light came on just now.
Expert:  George H. replied 1 year ago.
We can check that later if necessary. Nothing we have done to this point would affect the engine system. Always when you are making these tests you have the black lead to ground unless I direct you to do otherwise. Test the fuse with one meter lead grounded. You should show battery voltage at one of the sockets for the large fuse, look that it is not burnt in the window on top. On the red 10 amp touch the red lead to the testpoint then to the other testpoint with the black lead on ground and both testpoints should measure 12 volts or more. Thanks
Customer: replied 1 year ago.
Engine on, blower on full, 40 amp fuse under hood shows 14V. 10 amp fuse under dash shows 13.8V from top testpoint, 00.0V from opposite testpoint.
Expert:  George H. replied 1 year ago.
Replace the small fuse. The rest of the system should come back online. If you need to go to an auto part store for the fuse have them check the check engine light and see what code is stored. Let me know if that helps Thank you

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