Blower Motors Works on speeds 3/4 but not 1/2 - FIX + How-To

[Syndacate]

This is a common question and it's a relatively simple solution. This happens to a lot of cars, not just Honda Civics, my friend's SVT (tarus) blew one of these once a month. Alright, let's take a look at how fan speed is controlled on a blower motor. First you need to understand "how" basic electricity works in laymens terms. Volts = The amount of power Amerage (amps) = How fast the power is flowing Resistance = Measured in Ohms, slows down current (lowers amps) So your fuse box is basically the hub of electricity for your car - it's the distribution point for all the electrical devices, from your moonroof, to your dome light, to your VSS, to your headlight, the fuse box is the electricity hub. Now, they could have just made a hub with multiple ports, but that wouldn't make sense. Why? Fail-safe. If you had just a hub instead of a fuse-box with individual fuses - if something was to short out - it'd blow every other electrical device in the car - not a good thing. With that said, it's important to note that all devices in the car operate on the same amount of electricity - ~12v. Now, even though all of them operate at 12v, the reason why your headlight consumes more than your dome light is because of the amps - the flow of electricity. Now, for the blower motor: Let's say it takes the standard 12v to power the blower motor (it does). If you hooked up the power terminal to your battery with resistance down to 7.5a and grounded out the negative, it'd work fine spinning at 100%. Okay, so the blower motor runs off of 7.5a. For arguments sake (and sake of explanation) let's just say it runs off of 20a (which is like high beam headlight power, but whatever). Also, for arguments sake we'll use even numbers so everything turns out peachy. In line from the climate control switch to the blower motor is a "resistor pack." When you have your fan speed at 4 (or the highest), the 12v runs the blower at 20a - no resistance, and it spins as fast as the motor can safely run (without burning out). Now say you switch it down to speed 3. Now it still runs the same 12v, but it switches to a line where there's a resistor with enough ohms to kick it down to 15a. Now the blower motor doesn't have as much of a flow of the 12v going to and it moves slower. Now say you switch it to speed 2. Now it switches to an inline resistor that slows the current down by 10a - so now it's 10a And the same goes with 1, the lowest speed, the switch switches over the current to a line where it has the largest resistor - let's say 15a, which puts the total current at 5a - at 12v. So now it's got power, but is spinning slowly. As far as "off" goes? It simply works as a on/off switch between the fuse box and the blower motor. Clever way to use one wire, eh? So where are all these resistors? A resistor pack. Now different cars have the resistor pack located in different areas. On our Hondas, it's ontop of the blower motor, on some cars, it's on the rear of the climate control. The general cause of speeds 1/2 not working and 3/4 are working fine - is a blown resistor pack. Like I said before, this is a very common problem, swapping the climate control will NOT fix this (unless the resistor pack is on the rear of the climate control - which isn't the case on '92-'00 Civics. So this is a cheap and common thing to check first. Now, PLEASE don't confuse the resistor pack as a FUSE. It is NOT, a short will NOT blow this, it will blow the fuse in the fusebox - so don't think that just because your resistor pack blew, that you have an electrical problem. They go because they operate EXTREMELY hot (even hotter if you're always using it on the lowest speed) and then one of the resistors (which is about 1/3 the diameter of a paper clip) burns through and that's that. So don't get stressed if yours goes, it's most likely not an electrical problem, just "goes" like a headlight bulb would. So how do you replace the resistor pack? 1) You buy a new one...obviously, mine went on my '97 civic - I replaced it, here's what I bought for it: A WELLS JA1258 Resistor. Box it came in: And Receipt, as you can see, only $30 tax included: How to replace: #1: Open Glove Box. #2: Push sides in by rubber stoppers so it can pull down. #3: Let all your shit in the glove box fall to the floor. #4: You can opt to remove the glove box, it's unneccessary, if you do there's 2 screws on each latch (2 latches) and it comes down. Circled in RED is the resistor pack. Circled in BLUE are the mounting screws for it. #5: Unscrew the screws circled in blue in the above picture. It's a bit of a tight space, so I just used the head of a multi-headed screwdriver. #6: The resistor pack lifts up & out of the hole. Now, if you don't see any of the resistors (coil parts) broken - don't think "oh - it's still good" - sometimes (in my case just recently) they "go" but don't physically break in terms of what you can see. Circled in red is the harness clip - unclip it, and remove the resistor pack. #7: Here's the old resistor...it was only broken (by the naked eye) b/c I tossed it aside, when I first pulled it out it was all together. Toss that shit in the garbage. #8: Get the brand new one out of the box and plug it into the harness connector. #9: Put it back into the hole and screw the mounting screws in. #10: Push the sides of the glove box in to get the rubber stoppers around the stop pegs and lift it back into place. #11: Put all your shit back in there - it should be in a nice, neat, pile on the floor . Enjoy 4 fan settings of air control, as I can currently drive my civic w/ the AC on w/o freezing my nuts off and w/o burning up. You might wanna also take note that "3" is the best setting whether it be for AC or heat (anything except the defoggers). The reason being is that when the fan is on speed 4, it throws air out too fast to be cooled by the freon, or if you have the heat on, it's too fast for the heater box to heat it up. On the flipside, if you're trying to defog your windshield, you want the most "air" up there - so 4 is better. ================================================== ===== Well, I hope that helps some people out. Note that this is not always the fix, sometimes the climate control switch is broken. Though if this is the case usually all of the speeds don't work, or just one doesn't work. Though a blown resistor pack can make all speeds not work if it's blown in the right place - so I'd try replacing that first.

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[slowcivic2k]

To those that would like to see the circuit in action, I will add to this thread.



As you can see from the picture above, there are 4 rotary positions in this civic dial. If you examine the blower resistor in this picture, you will see how current flow through the dial and attains the correct speed. It does this by creating a resistance as he stated above, and I will use 5 Ohm's in this case for each squiggly line in the blower resistor.

As you see in the 4 position (red wire) the current is unopposed, and travels with full voltage to the blower for max speed. You blower works in high only because there is a separate ground line from the resistor box that has no added resistance, and thus gives you high only, even if the resistor is faulty.

Position 3 (blue) goes through the resistor, and one squiggly line (5 Ohms) This will give a slightly lower speed than max because of the voltage used to pass the resistor. If the resistor that this position uses fails, the entire unit fails, because the other two positions require passage of this squiggly line to obtain the next lower speed.

Position 2 (green) Goes the same route, but it passes through two squigglies (10 Ohms) which gives the next lower speed. If the second resistor this position uses fails, this position, and the 1st position will fail, because the first uses this to obtain the next lower speed.

Position 1 (purple) Takes the same route into the resistor, and passes all 3 squigglies, for 15 Ohms in this case, of resistance, obtaining the lowest speed setting. If this third resistor fails, this position will not work, but 2, 3, and 4 will, since none of those positions use the third resistor.

Why it fails:

Resistors produce heat by soaking up power, and after a while, they can fail, by either overheating, and in some cars, water entering the blower since some units are cooled by the blower motor air. The lowest speed setting will use the most current, as it must pass through all 3 resistors in this case to obtain its speed, and is the most likely to fail, resulting in only high speed.

Not to steal from Syndacate, but just adding another way of seeing it. I hope it helps you all.

[Syndacate]

Originally Posted by slowcivic2k

To those that would like to see the circuit in action, I will add to this thread.



As you can see from the picture above, there are 4 rotary positions in this civic dial. If you examine the blower resistor in this picture, you will see how current flow through the dial and attains the correct speed. It does this by creating a resistance as he stated above, and I will use 5 Ohm's in this case for each squiggly line in the blower resistor.

As you see in the 4 position (red wire) the current is unopposed, and travels with full voltage to the blower for max speed. You blower works in high only because there is a separate ground line from the resistor box that has no added resistance, and thus gives you high only, even if the resistor is faulty.

Position 3 (blue) goes through the resistor, and one squiggly line (5 Ohms) This will give a slightly lower speed than max because of the voltage used to pass the resistor. If the resistor that this position uses fails, the entire unit fails, because the other two positions require passage of this squiggly line to obtain the next lower speed.

Position 2 (green) Goes the same route, but it passes through two squigglies (10 Ohms) which gives the next lower speed. If the second resistor this position uses fails, this position, and the 1st position will fail, because the first uses this to obtain the next lower speed.

Position 1 (purple) Takes the same route into the resistor, and passes all 3 squigglies, for 15 Ohms in this case, of resistance, obtaining the lowest speed setting. If this third resistor fails, this position will not work, but 2, 3, and 4 will, since none of those positions use the third resistor.

Why it fails:

Resistors produce heat by soaking up power, and after a while, they can fail, by either overheating, and in some cars, water entering the blower since some units are cooled by the blower motor air. The lowest speed setting will use the most current, as it must pass through all 3 resistors in this case to obtain its speed, and is the most likely to fail, resulting in only high speed.

Not to steal from Syndacate, but just adding another way of seeing it. I hope it helps you all.

The illustrated version .

Thx

[satitus]

Perfect timing on this thread. I just read up on it and fixed my blower issue (fan speeds 1 and 2 dead). FYI in the advance auto parts online section, the part is located under replacement parts>switches>blower motor resistor. The borg warner part is RU801.
The OEM acura part number is 79330-SR3-A01 and is cheaper than the borg warner part (online).

[DSMAddicted]

Excellent post, well written, thorough and informative, thanks!!!

-Walter

[MelJ]

I sent a PM to the OP, but I think there may be some differences in the setup from one used here. I have a 2000 Si and here is what it looks like for mine

The resistor I got was from Amazon and the guy f'ed up the first one, but actually got me an OEM one from Honda in return.
Here's the pic of where it sits at

The base of mine actually sits in the area secured by the clips. I don't know how to get the damn thing out. Any suggestions? Sorry about the size of the pictures. I took them with my phone.

[JG90CRX-Si]

Wow, I wish I would have known about this a long time ago instead of freezing my nuts off too!

JG

[TekBuDDy]

i just changed my resistor and nttin changed, itsmoked up and the blower motor turned red. none of my fan speeds work. i know its getting power cuz whenerver ichange the speed my idles lowers

[Ultimate Collision Center]

I am having the same issue with my 96 jdm civic Si 4dr...mine looks completely different and is on the left side of the car.. but its just a small metal circle thing and not a resistor like urs...i am thinking my issue is the climate control unit...