RotorBeav15

I recently had a failure of the cabin blower motor in my 2004 LX. I went through the troubleshooting tree found here:


http://troubleshootmyvehicle.com/hon...blower-motor-1


I have determined that the fan is good, as it passed the bypass test. The fuses are also fine. I also ran the tests on the original resistor and came up with 1510 ohms on the resistance test and about .5V on the diode test. After much frustration, I took it to the shop expecting a short (I ran the diagnostic test and came up with the 12 flashes of the AC light). They determined it was a short in the Blower Motor Resistor itself. Not wanting to pay for them to put it in (and the part wasn't available...) I bought one and did it myself.


I installed the resistor yesterday and the cabin fan worked fine for my drive to work. When I started my car again 10 hours later, I was left with the same problem as before. A full day later it is still not working with either resistor installed. I checked the fuses and motor again, those are still fine. The resistor I removed was a DENSO. The replacement was not (and it worked for one trip in the car).


Does anyone have any ideas what I may be running into here? I'm hoping it's as simple as getting another DENSO resistor and trying the swap again. All ears for any advice or guidance.


Beav

ezone

Smack the bottom of the fan motor and see if it will run again

Recheck that the new power transistor is actually bad...take it back to the parts store and see if they will warranty it

Measure amp load of the blower motor while the transistor is bypassed (direct ground to the motor), if it's drawing too many amps to run it can blow the thermal fuse inside the power transistor

Check/replace the cabin filter set, poor airflow can overheat the power transistor and it can blow the thermal fuse inside the power transistor


Goggle search for how to repair honda blower power transistor, repair the original unit and use it as a test part

RotorBeav15

Would a cabin filter/overheat issue be the culprit if the wires from the fan to the resistor were hanging below the glove box? I left it disassembled to be sure before I put it all back together.


What he amperage should I be looking for?

RotorBeav15

I checked the resistance and came up with 1515 ohms. Voltage drop on the diode test was ~.5-.55V.


I suppose however that none of those indicate an overheating problem.

ezone

Wait a minute....You left the power transistor OUT of the blower housing?

If so, then you ruined it.
It MUST be installed in the housing because it needs the fans air flow to keep it from overheating.

CraigW

iTrader: (1)

That seems to happen rather quickly... if your lucky it just opened the TCO, and you can replace that.

Dadrider

What is the TCO? I can power up the blower with a 12 volt source, and it looks like the Resistor is passing the checks in the link below.


My Resistance was about 1470 ohms and the power drop on the resister was about .430 volts.

Now what?

CraigW

iTrader: (1)

A good test if TCO (Thermal Cut Off) is open, is to lower the glove box & remove cabin filter. Set blower to on, then watch to see if the fan spins a short tiny bit when ignition is 1st turned to position II.

If it does spin a short bit then TCO is open.

Dadrider

Craig, I'll try that this evening when the car gets home ! Thank you.

Dadrider

Guys, yes the resistor is back in and when the key is turned on the fan spins or pulses a little. I am looking all over for the TCO. Where does this little bugger live?

CraigW

iTrader: (1)

https://www.civicforums.com/forums/3...ght=transistor

Get a TCO, do NOT use a resistor.

Dadrider

Pulled the resistor, took it apart and it reads 0 ohms. At least I found it.

CraigW

iTrader: (1)

Did you Ohm the TCO ??

Will read infinite if it is open.

Found a 115 degree C TCO on amazon, for about $6

Dadrider

Yes I did locate the TCO and ohm at that point. I'll look for the amazon part and see what I can come up with.

Thanks for the help !

Jeff

CraigW

iTrader: (1)

Make sure your cabin filter is in good condition, to prevent new TCO from opening.

If you need to solder it.... use needle nose pliers to keep the heat from opening new TCO.

honda.lioness

A substantial edit to my original post follows.

Somehow I managed to let my cabin air filter get all crudded-up, overloading the motor, and blowing the TCO fuse (inside the blower resistor unit). The OEM TCO is rated for normal operation at 114 C. I could not find an aftermarket TCO of this rating locally. On the net I saw people say they used Radio Shack TCO stock number 270-1322 (129 C) and 270-1320 (140 C). I bought an aftermarket TCO rated for 129 C. Some on the net cautioned about the fit of the higher rated temperature TCOs. They are larger in diameter and longer. The TCO packaging has caution about bending the terminals too close to the TCO body. I crammed my aftermarket TCO into place. It did not fit well in the resistor unit's holder. I think the net has some comments about how this contact with the holder is critical. I did not add any conductive paste(?). I bent the terminals of the aftermarket TCO mightily to get them through the holes in the resistor unit circuit board. The resistor unit's cover did not snap into place easily. I did the checks at http://troubleshootmyvehicle.com/hon...esistor-test-1 and thought all was well.

Several days later, I drove to the countryside for a hike in warm weather. My blower's operation was erratic after about 20 minutes. It would advance to a higher speed when I turned the speed control **** lower. When I turned the **** to the off position, the blower kept running. The A/C would go off spontaneously while the blower kept running. After half an hour of this, and worried about the effects on the blower motor, I pulled over and disconnected the blower resistor. When I got home, I removed the resistor (it's now super easy to remove after all the practice). It tested fine. I figure the bad fit or bad soldering was resulting in disconnections when all got hot.

Several models of Hondas use this fuse and resistor unit. After the failed attempt, I bought an aftermarket version from eBay for under $10. Meanwhile I did the quick fix of shorting out the TCO's two terminals. For the quick fix, I used this this site: http://honda-tech.com/honda-civic-20...istor-2041582/. The latter has great photos.

I have not taken a really long drive yet, but so far, the blower seems to work fine as a temporary fix. Importantly, without an actual TCO, there's no thermal protection and a risk of fire should something suddenly go wrong to reduce cooling air flow over the resistor unit. I am running the blower with caution until the new resistor unit arrives.

honda.lioness

----

CraigW

iTrader: (1)

Just like with a fuse, you could use smaller amperage (for TCO lower temp) but never a higher amperage fuse, or higher temp TCO.

honda.lioness

Craig, I thought about this a lot yesterday. One can argue using the higher temp TCO is a shadetree mechanic fix. The "fix" trades expediency, grabbing the nearest part that is 'good enough for now,' for risk. I weighed all of the following before going with the 'less safe' TCO.

I believe what the TCO is protecting is the motor winding insulation. If the temperature is too high, the insulation degrades, leading to motor failure. From one site: "Maintenance experts agree that excessive heat causes rapid deterioration of motor winding insulation. The common rule states that insulation life is cut in half for every 10 C of additional heat to the windings. As an example, if a motor that would normally last 20 years in regular service is running 40 C above rated temperature, the motor would have a life of about 1 year."

I quickly ruled out just shorting the two terminals of the TCO, with either a low resistance piece of scrap wire or 1 ohm resistor. Then one has no thermal protection for the motor, as folks here know.

From a guy with a Honda Pilot: "After running my rear AC on a particularly hot day, I pulled the transistor unit and checked the temp. It was running at 140*f (60*c). As you can see that is a long way off from the advertised rating of 237*f (114*c) on the stock thermal fuse."

I see reports on the net that the Dodge Caravan uses a 141 C rated TCO.

From various sites: "A general rule of thumb for continuous operating temperature for thermal cut-offs is 30 degrees C less than the Maximum Opening Temperature."

The maximum opening temperature on the OEM TCO is 150 C.
For the NTE 8125 TCO I installed as a replacement, it is 155 C.

There are several temperature specifications for TCOs. I contemplated these spec sheets:

http://www.nteinc.com/specs/8000to8999/pdf/TCOs.pdf

http://www.mouser.com/catalog/specsheets/XC-600225.pdf

Also, yesterday, I handed the OEM TCO to the older gentleman at my local electronics shop, and before I could get the temp spec out of my mouth, he said "114 degrees C" and went to the back to find a replacement. He did not seem concerned about the 114 C operating temp rating of the original TCO vs. the 128 C operating temp rating of the replacement he proposed.

I guess one could argue that, when the cabin filter is clogged, my blower motor might be running at a temperature about 5 degrees C higher for some time with the higher rated TCO. That is, with the OEM TCO, it would normally run at 149 C (give or take) before the OEM TCO blew at 150 C. With the TCO I used, it would run at 154 C (give or take) before this TCO blew at 155 C.

My cabin filter got particularly clogged because of winds and dust this time of year where I am. For me the rule now is: Shake out the cabin filter at least once a month in the Spring or when doing any dirt road driving.

Colin42

How long had the cabin filter been in there before it failed? Shaking it out once a month seems like overkill unless you're doing a ton of driving.

CraigW

iTrader: (1)

I feel the TCO is protecting the transistor assembly. Someone posted up that they tested their system before mounting the transistor into place and it opened the TCO. (when it is in place it is cooled by the operating blower fans air flow, and a plugged cabin filter also restricts proper flow)

ezone

Definitely agree, because the TCO is attached to the power transistor assembly.

There is no way for it to detect what the blower motor temp might be.

honda.lioness

I last blew out the cabin filter about six months ago. The other day when the TCO failed, I found the filter full of dirt. I do drive on dirt roads from time to time.

CraigW

iTrader: (1)

The MM would only call for it after 25k miles, same with engine air filter.

6 months seems an awfully short time, Maybe your local dirt is clogging the filter.

Are you in the West ??

Colin42

Like Craig says that seems like a really sort time for the filter to get clogged like that. Might want to pop the cowl cover off and see if something's stuck in there dropping dirt into the filter area.

honda.lioness

I thought of this, but then when the TCO opens due to overheating, it seems to me that dealerships replace the whole resistor unit. I saw nothing in the OEM service manual about un-soldering and then re-soldering in a new TCO. But I hear you and ezone regarding how the TCO is not all that close to the blower motor and so you all think it is not protecting the motor. Perhaps the high temperatures that the resistor unit experiences via normal operation, made even higher by say a blower motor failure (independent of the resistor unit failing) or air filter blockage, are a fire hazard or would melt the various plastic components in and around the resistor unit. Hence the need for the TCO, securing all power to the blower and resistor unit.

honda.lioness

I am in the southwest, driving in something like 30 mph wind now and then, with the wind whipping every which way (relative to the car's direction of motion). I check my engine air filter at least twice a year. It is never as full of debris and dust the way the cabin filter is.

Colin, I will take a look.

honda.lioness

My repair failed miserably yesterday. See the edit to my first post above.