Blower appears to be okay. Connected it to a power supply. It was spinning freely without much noise and draw about 10A at 10V. Unfortunately couldn't go higher because the power supply was hitting its limit. I suspect it'll draw about 13A at 13V linearly. Next step is to apply a resistive load onto the blower power connector.

 

probably blown... I know the Vibes usually go through blowers like crazy, I figured the Matrix did as well and maybe the Corollas, but we use different PN's.

Try a new one and see if that works, I can't see any electrical problems other than maybe a chewed up wire somewhere causing this issue.

 

Fortunately I do have access to another car with the same blower. I will try a swap. However, I am leaning toward maybe the relay. I applied a dummy resistor load, and it does nothing. But if that resistor load is extremely small, then I can get the A/C light to stay on.

 

If it's not working on any setting, I would suspect the relay (HTR Relay), the blower motor resistor, the wire connecting the coil side of the relay to the blower switch, or the blower switch ground.

At your mileage, the likely culprit is an open circuit at the internal fuse of the resistor. The relay would be my 2nd guess.

 

Car: 2005 Corolla S automatic with 245K miles still on original parts (except torque converter).

I have been searching on google and this forum for blower not spinning. This one came closest http://www.toyotanation.com/forum/1...com/forum/132-corolla-9th-gen-1st-gen-matrix-2003-2008/1207490-no-blower-c.html but there has been no activity since 2015. My car is 245K miles still on original equipment. The blower just stopped spinning yesterday without making any kind of noise. It was working great before. Air flow was smooth and the speeds worked fine. It just stopped suddenly. Started the engine and the fan wasn't turning on.

My symptoms:

1. Broke down without any prior warning of being bad.
2. Blower fan doesn't spin in any of the speed setting.
3. Turning on the A/C doesn't do anything either.
4. A/C light remains off even fan is set high in all speed settings.
5. Blower fan doesn't spin even if I manually give it a manual assist.
6. Blower fan makes no sound whatsoever like struggling to turn on.

My first diagnosis attempts:

1. Using Corolla 2005 document # OM12891U, the fuses # 28 (A/C 10A), # 35 (M-HTR/DEF I-UP 10A), and # 41 (HTR 40A) - all appear to be good. Checked with ohm meter and continuity meter.
   
2. I took out the blower fan. The power connector to the blow reads about 11.70V on all speed setting of the fan. However, it read 4.75V at one point in time on low, med, and high. I could not get it to read 4.75V again. This was tested with a voltage DMM so there was no loading on the blower resistors or the power source. Now it always read about 11.7V with the engine off or about 13V with engine on.

What is the condition to turn on the A/C light? Does the fan need to spin before this is turned on?

What I have not done yet:

• Haven't checked the relay (where is this located?)
• Haven't checked the blower resistors (where is this located?)
• Haven't checked the switch connector (where is this located?)
• Haven't checked the blower yet (to be done tomorrow)

Is there anything that I missed? I am having a tough time finding the location of the relay, blower resistors, and the switch connector. Unfortunately my googling was not successful. I found the 2004 Corolla wiring diagram but had no luck with 2005, 2006, and 2007. Thank you!

Sorry, might be too late for you, but might help someone else...

10-06-24. 2003 TOYOTA COROLLA (190,000 miles) - Intermittent blower fan operation – BLOWER RELAY LOCATION, ID and REPLACEMENT.

After you have checked fuses, blower motor (for normal operation and obstruction of fan), resistors, connectors/wiring, and speed selector switch and the blower is still intermittent. There is a blower motor relay. I found very little online information about this relay and its location.

BEFORE PROCEEDING – DISCONNECT THE BATTERY AS PER MANUFACTURER INSTRUCTION FOR WORKING ON AIRBAGS SINCE THESE RELAYS ARE NEAR THE PASSENGER SIDE AIRBAG – THE MANUFACTURER MAY INSTRUCT TO REMOVE BOTH POSITIVE AND NEGATIVE CABLES FROM THE BATTERY AND DESIGNATE A WAIT PERIOD – I DO NOT HAVE THIS INFORMATION.

This information is intended for those familiar with automotive electrical circuits and testing. Unfortunately, I do NOT possess the manufacturer electrical schematics for this vehicle.

There are plenty of online videos for testing and replacing the blower motor, resistors, fuses and selector switch – I will not discuss those here. However, I found very little information about the BLOWER MOTOR RELAY.

VEHICLE OWNER indicated, at startup, frequently there was no fan (no A/C and no heat circulation). They would leave the fan in highest setting hoping it would come on. After driving for some time, the blower would come on and work in all settings, and then would stop and start working again at random.

MY TESTING confirmed the random operation, working selector in all positions a couple hundred times. At first it appeared to be a bad selector switch – not turning on with the lowest speed when moved from the off position. Tested the operation of selector switch and inspected the contacts, wiring and connectors – all looked good.

Obviously, fuses were okay. I removed and bench tested the motor and resistor module (someone online provided a basic schematic of the resistors, switch, and motor) and all checked out fine.

The partial online schematic showed +12VDC power going through a “rectangular box” (not an appropriate schematic symbol) and then directly to the motor. The fan speed selector provides the ground for the circuit to the negative side of the motor through the resistors (depending which speed is selected). The "box" is presumably a normally open relay contact.

I unplugged the motor connector and operated the fan speed knob and could hear a relay clicking from off to lowest speed and then again, back to off. Before this, I could not hear a relay clicking over the sound of the selector switch snapping into position nor over the noise of the blower motor when it was plugged in and would work. (When the blower did not work, obviously there was no relay clicking to hear.) The blower relay is energized as soon as the fan selector is moved from "OFF" position and will not "click" moving to other positions other than to and from "OFF."

Glovebox removed, I isolated the clicking to a black, plastic block above the glovebox opening. Reaching up on top of the plastic block I could feel three (3) ice cube relays and one was clicking with the fan selector – a larger, blue relay. (Denso #5670005 or #90987-04010). I do not know what the other two ice cube relays (black) control, but the center one energizes with the ignition key on and de-energizes with the key in the off position.

Ordered a new motor blower relay online for $14 but also was able to open the old relay and clean the contact by carefully flossing a thin strip of fine sand paper back and forth, then sprayed electrical cleaner (to remove sanding grit) and reinstalled it for a temporary fix. DC relay contacts are typically plated (e.g. gold) and once pitted and worn, will not work dependably for very long and may even weld themselves closed. I will replace the relay when it arrives.

Note: the black plastic relay block has two screws in the front and it may swing down for access. But I could not readily figure out how to do that and did not relish poking around the wiring near the passenger airbag which is above and behind the relay block. Also, it may be possible to go through the passenger airbag removal process to access these relays from above. I used a flexible fiber optic inspection camera - removal and installation of the relay took just a few minutes using the camera.

Hope this helps some of you!

 

Thanks for this information. It’s very detailed.

Here’s a bit of a twister. Back in 2020/2021, I was driving my corolla home with ac blaring. Ambient temp on dash reads 110 F. Make a stop and back in. Turn on ac, nothing. It was very hot driving home.

Get home and start doing diagnosis. First thing I did, pulled the heater relay on the firewall. This was because the videos I watched all suggested to check the copper contacts. They can short out. It was clean.

Then checked the ac mgt clt relay under the hood. Didn’t work at first. Swapped the relay with the horn as they were similar. Nothing worked. Like you, decided to go after the heater relay. Stopped because the gap between the dash frame and edges tore up my arm.

I tapped on the blower motor and that got it going. The beating started making noise. I even tested it with a 9v battery. It turned and was noisy. Replaced blower motor and all was good again.

 

2003 Toyota Corolla (190,000 miles) – Blower Motor Relay Location Troubleshooting without Schematics.

The only reason I posted at all is because I found so little information about where the blower relay was located, after looking in all the usual places. There were a few people talking about it on forums, and I knew there had to be a relay somewhere, but I did not find an online video or images. A service manual with schematics would have been very helpful, but who has those?

BEFORE PROCEEDING WITH ELECTRICAL REPAIRS – DISCONNECT THE BATTERY AS PER MANUFACTURER INSTRUCTION FOR WORKING ON AIRBAGS SINCE THESE RELAYS ARE NEAR THE PASSENGER SIDE AIRBAG – THE MANUFACTURER MAY INSTRUCT TO REMOVE BOTH POSITIVE AND NEGATIVE CABLES FROM THE BATTERY AND DESIGNATE A WAIT PERIOD – I DO NOT HAVE THIS INFORMATION.

This information is intended for those familiar with automotive electrical circuits and testing. Unfortunately, I do NOT possess the manufacturer electrical schematics for this vehicle.

Extreme temperatures (over 100F and below 20F) play havoc with mechanical and electrical components. In 46 years of working on cars, including repairing ventilation systems, mostly I have had to replace blower motors. A few resistor banks, fuses, and relays, too. So, when the fan stops blowing, my go to is to suspect the motor… especially if the fan has been making noise for some period of time before it stopped or slowed… and especially, if when you tap on it, it starts working again – assuming the tapping isn’t jiggling bad wire connections. Some motors are easy to replace (like the 2003 Corolla) and others, a complete nightmare.

Sometimes, the cabin air filter disintegrates and falls into the fan, or debris like leaves or rodents building nests or storing food for the winter will slow or stop them, too. (Preventing the motor shaft from spinning should blow the fuse.)

These DC motors are relatively simple and “cheap” but are exposed to extreme temperatures and humidity. The ’03 Corolla motor is mounted vertically, so any moisture or water, when the fan is off, can easily go down the motor shaft and into the motor… wetting the bearings and wiring. One of the worst things a car owner can do is never run the fan or always run it at only the lowest speed. It will still last a long time, but not as long as using it continuously and in the various speed ranges. (Some manufacturers prohibit you from completely turning off the blower, having only a “LO” setting, to ensure positive air flow through the passenger compartment. The ’03 Corolla allows you to turn the blower OFF.)

FUN FACT: When a fan duct is blocked off, and the fan is not moving any air, it draws very little current (i.e. amps). Intuitively, people may think it would draw MORE current. Think of it this way, when it is not moving air, it’s just “freewheeling” and using just enough current to spin the shaft and the motor is not really doing much work. When the duct is NOT blocked, the motor is moving lots of air and is “working hard,” so it uses more current. [QUIZ: So… if the cabin air filter is so dirty it blocks air flow, is the motor drawing more current, or less current, than a clean filter?]

In my original post, in an attempt to keep the information concise, I omitted a lot of information about the troubleshooting steps and considerations I took:

1. The original complaint was simply that “the A/C was going on and off.” The owner’s son was driving 140 miles per day for work and had plenty of time to witness the “intermittent operation of the A/C.” With a few questions over the phone, I was able to determine it was the fan that was going on and off, and not necessarily a problem with the A/C. (In the morning it was cold and there was also no heat or defrosters.) In the ’03 Corolla, when the blower relay fails to pass +12 VDC to the blower, the light on the A/C button goes out, making it look like the A/C (and heat), in this case, was going on and off – but it is just intermittent fan power. I could explain the connection if I had full electrical schematics, but it’s moot at this point since the problem is fixed. Another “clue” when I was testing it, is that the A/C button light would not just go full on and full off but would go dim or flicker – indicative of a bad connection (added resistance) somewhere – in this case, pitted and dirty contacts of the relay.

2. For the record, I did eventually replace the relay ($14) when it arrived in the mail. I had cleaned the old relay contacts, as I mentioned in the original post, and that was temporarily working. But relay contacts are typically plated for long life. Especially DC contacts (often gold plated) because the electrical arc (or “spark”) is always in “one direction” and burns off this coating on one side more quickly than the other. Once pitted and burnt, you may be able to get them temporarily working again by cleaning them, but they won’t last very long. It’s time for a new relay.

3. It is now obvious to me that the fan speed selector switch has a separate contact that energized and de-energizes the illusive power relay between OFF and any speed – this would be clear on the wiring schematics for this vehicle, if I had had them.

4. I used a cheap automotive stethoscope to locate the origin of the clicking sound in the cavernous opening with the glovebox removed.

5. Japanese machine (and auto) manufacturers often prefer “sinking” control circuits – controlling the negative or ground side to complete an electrical circuit – like the '03 Corolla fan control connecting the ground or negative side of the motor through the resistors to make the motor work. American manufactures historically “source” control circuits – controlling the +12 VDC side. It does not matter which way it is done – it is just “a convention,” though there are plenty who will argue which is better. Today, it’s a mixed bag of both and you cannot assume - it helps to have a schematic, like the partial one I referenced someone had provided online (see below). (BTW, I’ve heard the “sinking/sourcing” arguments for over 40 years, so let’s not go there, okay? Also, which is better - “grounded vs ungrounded” control circuits… heavy sigh.)

6. Before I located the relay, I unplugged the motor and connected a DC volt meter to the +V wire at the motor, and the negative meter lead to ground (sheet metal inside the dash). Voltage was intermittent with operation of the speed selector and varied from 1 to 12.8 volts, including hovering around 4 volts for a period of time. (This is due to the contact being pitted and very dirty. Likely, the original contact plating has been burned off, too.)

7. WARNING: DO NOT TRY THIS. YOU COULD BE BURNED OR START A FIRE. Before I found the relay up inside the dash, I took a heavy wire (#10 AWG THHN wire) from the + terminal of the battery directly to the motor plug and the motor operated fine in all speeds. I did not run it for long this way, it just proved there was a relay somewhere keeping +DC power from the motor. DO NOT TRY THIS: if you use too light of a wire or the wrong insulation characteristics, it can melt, burn you, and/or catch fire. Also, you must be very certain to NOT touch the negative connector on the motor, or any grounded metal - that would be a dead short across the battery and get very hot or catch fire quickly.

8. WARNING: THE RESISTOR MODULE GETS VERY HOT! THE MODULE CAN BURN YOU OR START A FIRE. In testing with power on, the resistor module can be removed and left hanging from the wire harness on the passenger side floor. BE SURE THE MODULE DOES NOT COME IN CONTACT WITH ANYTHING THAT CAN MELT OR CATCH FIRE! The module is intended to be properly mounted inside the duct and in the airstream of the blower to help keep it cool. DO NOT RUN THE FAN FOR ANY LENGTH OF TIME WITH THE RESISTOR MODULE UNSECURED FROM ITS INTENDED LOCATION – BE AWARE THE RESISTOR MODULE CAN BURN YOU OR START A FIRE.

As you go up from lowest to highest speed, the total resistance for each are approximately 3.75 ohms, 3 ohms and 2 ohms, so roughly 50, 65 and 100 watts of heat is generated, respectfully. Just like an old, incandescent bulb of the same wattages (50W, 65W, 100W), you know these get very hot and you would not want to touch one, and you may even recall someone starting a fire by throwing a towel or clothing over a lamp with an incandescent bulb back in the day – it is the same thermal danger for these resistors. On HIGH speed, there is a direct ground connection to the motor (no resistors in the module are used – see diagram, below) and so, on HIGH setting, it is the full current to the motor for full speed – whatever that motor needs to draw under the load it "sees" moving the air it’s moving.

9. My last resort, if all else failed, was to (what we call) “fat finger” or trace the one +DC wire from the motor back to wherever that relay was. "Last resort," because wires travel in bundles, are usually tightly wrapped, go many different directions out of these bundles, often all look the same when not color-coded, are routed through tight spaces, are secured with anchors here and there, it’s dark and difficult to see, and you have to be willing to contort your body in all sorts of ways. It is also a chore to put everything back properly - the way it was originally. The interior “dash harness” is a carefully designed bundled-up-spaghetti-mess of wires with dozens of connectors and anchor points, installed early in the vehicle assembly process before everything else gets installed, like the dashboard, airbags, trim, consoles, panels, controls, steering wheel, etc. It is one of the physically tougher assembly line jobs and must be done without error.

10. Be aware that relay contacts can not only fail to close (pass current), but they can also “weld” themselves closed (be stuck in the ON state). In this case, you might experience the fan not shutting OFF when you turn the ignition switch OFF. If the driver does not notice the blower is still running when they leave the vehicle, they could return to find a dead battery.

11. Hope this helps some of you.

12. Here is the partial schematic I saw online that I redrew from my notes. Note that I did not include the contact that energizes the “illusive” relay coil off the fan selector switch because, technically, I do not have the information. Just know that the relay coil energizes (passes +VDC to the motor) anytime the selector is in any speed and de-energizes (opens the +VDC to the motor) in the OFF position.