infidex Posted June 23, 2008 Share Posted June 23, 2008 I have a 2004 Honda Accord EX with 4 cylinder, 40,000 miles. The A/C was running the other day, drove for about 30 seconds and all of a sudden the blower stopped running. - I have checked all the fuses and relays for the blower motor, all good. - I have by passed the transistor box (resistor box) connecting the blue and black, and the motor will run (Motor is good!). - The compressor isn't engaging when I turn on the A/C. If I am low on Freon, will the low pressure switch keep the control module (radio module with a/c controls) from allowing the blower motor to kick on? Any help would be appreciated. I'm going to bypass the low pressure switch to see if I can get the compressor to kick on tonight, I also have a meter to check connections. If anyone has a wiring diagram or any ideas, I would love to hear them! Link to comment Share on other sites More sharing options...
James Matteu Posted June 23, 2008 Share Posted June 23, 2008 transistor box (resistor box) Which is it? If you have an automatic climate control system, it should be using a relay/transistor combo, but manual systems would have a resistor in place of the transistor and lack a high motor relay. Be specific, even though it sounds like you will get to the bottom of this before we do. Keep in mind, regardless of which system you have, the failure of the motor itself tends to be inconsistent, see here. I was always able to get the motor to run if the current was high enough, but when the power was limited to 30A, it would come on sometimes and sometimes would stay off. Link to comment Share on other sites More sharing options...
infidex Posted June 23, 2008 Author Share Posted June 23, 2008 Which is it? If you have an automatic climate control system, it should be using a relay/transistor combo, but manual systems would have a resistor in place of the transistor and lack a high motor relay. Be specific, even though it sounds like you will get to the bottom of this before we do. Keep in mind, regardless of which system you have, the failure of the motor itself tends to be inconsistent, see here. I was always able to get the motor to run if the current was high enough, but when the power was limited to 30A, it would come on sometimes and sometimes would stay off. This is the part that I by passed and was able to get the blower motor to work, it says it is a blower resistor. Link to resistor It is the RU1092 part on the page. So I guess my question is, why does the blower not work when the compressor isn't working? If I by pass this resistor, I can get the motor on high, but no cool air (compressor not running). My only guess is that the pressure switch tells the radio/climate module to not turn on the blower. Also, if I turn on the heat, I get nothing either. I know my motor is getting juice since it comes on when I by pass the resistor, it seems that something is telling the control module not to let the resistor let the motor come on. Link to comment Share on other sites More sharing options...
crxtacy Posted June 23, 2008 Share Posted June 23, 2008 Blower motor has nothing to do with the A/C .It should come ON when you turn on the blower switch.If the fuses,relay,resistor and blower motor checks out okay like you said, i start by checking the blower switch and work my way towards the motor. Link to comment Share on other sites More sharing options...
James Matteu Posted June 24, 2008 Share Posted June 24, 2008 Blower motor has nothing to do with the A/C .It should come ON when you turn on the blower switch.If the fuses,relay,resistor and blower motor checks out okay like you said, i start by checking the blower switch and work my way towards the motor. +1 This is the part that I by passed and was able to get the blower motor to work, it says it is a blower resistor. Link to resistor It is the RU1092 part on the page. Okay, your system does use a resistor, not a transistor. So I guess my question is, why does the blower not work when the compressor isn't working? The real question is: why does your blower and you compressor fail to function. Besides, are you sure your AC isn't working? Have someone toggle the A/C switch while you listen under the hood, see if the compressor is clicking on or not. To answer a previous question, if your refrigerant pressure is out of spec (too high, or too low), the A/C circuit will not receive voltage. Link to comment Share on other sites More sharing options...
infidex Posted June 25, 2008 Author Share Posted June 25, 2008 If my resistor block is bad for the blower, will that prevent my A/C pump from running? I have by passed the resistor and the A/C pump still does not come on but the blower will, wondering if my resistor being bad could cause this? What I know.... - Blower motor is good - resisitor (could be good or bad, bypassed it to check motor) - fuses are all good, swapped relays and no change so assuming relays are good. There is one relay under the blower motor, I did not swap this as I don't have a spare, not sure what this one is for. I have electrical schematics if that will help anyone help me with this problem. Link to comment Share on other sites More sharing options...
James Matteu Posted June 25, 2008 Share Posted June 25, 2008 If my resistor block is bad for the blower, will that prevent my A/C pump from running? No. I have electrical schematics if that will help anyone help me with this problem. Your going to have to. Do you have automatic climate control, i.e. can you set the temperature in your car? Link to comment Share on other sites More sharing options...
infidex Posted June 25, 2008 Author Share Posted June 25, 2008 No. Your going to have to. Do you have automatic climate control, i.e. can you set the temperature in your car? It has dual climate controls, turn to low it says "lo" then you get readings from the 60's up to 80 for temperature settings, then "hi". I'll scan the schematics and post them shortly. Link to comment Share on other sites More sharing options...
James Matteu Posted June 25, 2008 Share Posted June 25, 2008 Your mention a relay on the bottom of the blower, sounds like you have a transistor. I checked the Honda parts catalog, and it shows the Transistor (not Resistor) mounted to the evaporator. Now given the aforementioned along with your description of the HVAC operation, it sounds like it is definately a transistor; the description given on the site you referenced may have been incorrect. #11 below is the Transistor. Link to comment Share on other sites More sharing options...
infidex Posted June 25, 2008 Author Share Posted June 25, 2008 Sorry, I've been calling it a resistor, but it is a transistor. It is labeled as a transistor on the wiring diagram. When I bypass the transistor, I get power on the blower (so I know motor is able to run with power), but the compressor is not running. Would this transistor being bad, keep my A/C pump from running? I have all the lights working for the A/C buttons, just like the car thinks everything is on and working, but no blower/compressor. I'm scanning wiring diagram as we speak, will upload shortly. Also, my controls for HVAC are on the radio, looking at the Chilton book, it looks like this is the manual climate control system (radio control module) versus the higher end climate control. Link to comment Share on other sites More sharing options...
infidex Posted June 25, 2008 Author Share Posted June 25, 2008 Here are the wiring diagrams for my car. Link to comment Share on other sites More sharing options...
James Matteu Posted June 26, 2008 Share Posted June 26, 2008 Okay, where is the mystery? It is obvious the the blower and A/C are completely independent of each other. The control unit regulates switching voltage to each, but neither interupts ground to one another, nor does either provide a feedback signal to the control unit that is able to interfer with the operation of the other. You may have two independent failures. Pick one to start with. I say the blower. The diagram shows a resistor built into the transistor, resistors can get hot and fail or mess with the "gate" function of a transistor. Run tests on that first, then do the usual: check all grounds, verify connectivity between all points, etc. The A/C may be fine electronically and just low on refrigerant, this verification can cost money, so fix the blower first. Did you ever verify the A/C function like I suggested? Have someone toggle the A/C switch while listening to hear if the A/C compressor clutch switches on and off. Link to comment Share on other sites More sharing options...
infidex Posted June 26, 2008 Author Share Posted June 26, 2008 Okay, where is the mystery? It is obvious the the blower and A/C are completely independent of each other. The control unit regulates switching voltage to each, but neither interupts ground to one another, nor does either provide a feedback signal to the control unit that is able to interfer with the operation of the other. You may have two independent failures. Pick one to start with. I say the blower. The diagram shows a resistor built into the transistor, resistors can get hot and fail or mess with the "gate" function of a transistor. Run tests on that first, then do the usual: check all grounds, verify connectivity between all points, etc. The A/C may be fine electronically and just low on refrigerant, this verification can cost money, so fix the blower first. Did you ever verify the A/C function like I suggested? Have someone toggle the A/C switch while listening to hear if the A/C compressor clutch switches on and off. The A/C compressor clutch is not working either, so no blower, no compressor clutch. Just seems odd that they would both go out at the same time that is why I wondered what would cause both to stop at the same time. Link to comment Share on other sites More sharing options...
James Matteu Posted June 27, 2008 Share Posted June 27, 2008 Each one shares a common ground in the control unit, I just hate to think that could be the problem since I don't know how to test the unit. I am stumped. Link to comment Share on other sites More sharing options...
infidex Posted July 2, 2008 Author Share Posted July 2, 2008 Just wanted to update everyone and this forum in case this happens to anyone else, PROBLEM IS SOLVED. Replaced the blower transistor box and the pump and blower now both work. Looking at the eletrical diagram, I couldn't see where the transisitor would stop the a/c pump from running, but as soon as a new one was installed, everything works again. Plug the old in, nothing works. Problem solved, and now there is A/C again for this Texas heat. Link to comment Share on other sites More sharing options...
James Matteu Posted July 2, 2008 Share Posted July 2, 2008 Horay! Link to comment Share on other sites More sharing options...
kgw Posted August 13, 2018 Share Posted August 13, 2018 Same problem as OP! Back from the dead! ? Any way, look at this Honda image: #11 is the Power Transistor. Is this what solved the OP's problem? 2004 Accord EX, 2.4 50k miles Link to comment Share on other sites More sharing options...
kgw Posted August 27, 2018 Share Posted August 27, 2018 Well, a new #11 Power Transistor solved my problem! Thankfully! Link to comment Share on other sites More sharing options...
sellatease Posted December 1, 2018 Share Posted December 1, 2018 maybe its as a result of cold climate location. you should do well to take it to the mechanic if it persist. Link to comment Share on other sites More sharing options...
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