09 Yaris Heater blower problem

[motoxxx3]

I have a very strange problem with my 09 Yaris 1.0 T2 (No aircon)
After 5-10 minutes of driving, the heater blower will suddenly slow down on it's own, then if I lift my foot off the accelerator after 1-2 seconds delay the blower will return to it's normal speed. If I press the accelerator it will immediately slow down again. It does it on all blower speeds.
The dealer has had the car for 6 days - changed the blower motor and the rheostat, but it has not fixed it! Currently waiting for a Toyota field engineer to look at it. Has anyone else had this problem? If so - what was the cause?

[CTScott]

Does your Yaris have the manual AC controls or the electronic ones? Either way, I would suspect the AC Amplifier, which is the ECU for the heat/AC.

[motoxxx3]

It has the manual rotary switch heater controls, with speeds 1-4 and the vehicle does not have air conditioning fitted, so Im not sure if it has an amplifier.

[CTScott]

It has the manual rotary switch heater controls, with speeds 1-4 and the vehicle does not have air conditioning fitted, so Im not sure if it has an amplifier.

I believe that even the non-AC ones have the amplifier. To check, take a look at the bottom of the air box for a black module about 50cm x 50cm x 4 cm. On your RHD car it will be at the bottom of the center console against the firewall in the driver's footwell.

[motoxxx3]

Thank you - I will take a look and see if it has one.

[motoxxx3]

I have just taken a look and directly underneath the airbox/ducting there is what looks like a silver module bolted to the floor directly behind the centre console.....printed on it - 'Made in U.K.' so it is likely to be be faulty :smile:
I will be annoyed with the dealer if it turns out it is this because it looks pretty easy to change..and they could have tried one off of another Yaris.
It's driving me nuts! it is as though somebody is constantly turning the blower speed up and down as Iam driving along

[CTScott]

I have just taken a look and directly underneath the airbox/ducting there is what looks like a silver module bolted to the floor directly behind the centre console.....printed on it - 'Made in U.K.' so it is likely to be be faulty :smile:
I will be annoyed with the dealer if it turns out it is this because it looks pretty easy to change..and they could have tried one off of another Yaris.
It's driving me nuts! it is as though somebody is constantly turning the blower speed up and down as Iam driving along

If the silver module has yellow connectors then you are looking at the SRS ECU (for the airbags). The AC amplifier is black and has one or two (depending on the configuration) white connectors.

[motoxxx3]

I have had another look, and the only other thing I can see is a black module with 'fins' on it. It is in bolted to the firewall in the centre of the car - directly in front of the silver SRS ecu behind the centre console.. difficult to see colour of the connectors/wires though. There does not seem to be any module mounted on the firewall in the drivers or passenger side footwells.
I just discovered last night & this morning that it seems like if Iam driving with the car's lights on the heater blower runs at it's correct speed all the time and does not fluctuate with accelerator position. If I turn the lights off it starts to fluctuate again.
Iam going to try this again over a longer period just to be sure.

[CTScott]

I have had another look, and the only other thing I can see is a black module with 'fins' on it. It is in bolted to the firewall in the centre of the car - directly in front of the silver SRS ecu behind the centre console.. difficult to see colour of the connectors/wires though. There does not seem to be any module mounted on the firewall in the drivers or passenger side footwells.
I just discovered last night & this morning that it seems like if Iam driving with the car's lights on the heater blower runs at it's correct speed all the time and does not fluctuate with accelerator position. If I turn the lights off it starts to fluctuate again.
Iam going to try this again over a longer period just to be sure.


Here's a picture of where it is located on my LHD Yaris. I believe that it is a mirror image of this for RHD cars.

36783

Looking at the European EWDs, yours definitely has one (even though it doesn't have A/C). The AC Amplifier has inputs from the headlight switch as well a from the alternator, that let it adjust the heating or cooling operation relative to those inputs. So, the problem being related to having the headlights on or off is quite plausible.

[motoxxx3]

Thank you very much for posting the photo.
You can see from the photos of my car that it is different to the U.S. spec car with aircon.
If my vehicle does indeed have a heater amplifier that is connected to the lights it is looking highly likely that this is the faulty component.

[CTScott]

Hmmm. The silver box is definitely the SRS ECU. If you want to PM me the VIN number for your car, I can verify through the electronic parts catalog if it has it, and if so where it actually is.

[CTScott]

Very interesting - The EPC shows the AC Amplifier as being "Not Applicable" for your VIN, so that explains why you can't find it. In that case, the controlling mechanism for the blower fan would simply be the HTR relay, which is located in the under dash fuse panel.

[motoxxx3]

Thank you very much for all your help Scott.
I know the dealer did not change the relay...and in my head I wondered if it could be the relay, or voltage regulator in the alternator.
Iam going to drive again tonight to see if it does not fluctuate with the lights on.
Really weird problem - I have never know a car to do this before.

[motoxxx3]

Tried it again last night, and with the lights turned on the blower fan speed does not fluctuate at all. As soon as I turn them off the blower speed fluctuates with accelerator position.
The Toyota dealer called me today, and they should have a field engineer out to look at my car next week.
I will update as soon as he has reached a conclusion as to what the problem is.

[motoxxx3]

The field engineer from Toyota G.B. ran some tests on the car yesterday, and it looks like the problem is a faulty alternator.
They have had to order me one in so I should get my car back tomorrow.
Not good for a car with only 4,000 miles on it.

[motoxxx3]

The Toyota dealer has just phoned me - the new alternator has been fitted and it has NOT cured the problem!
They have told me to keep the courtesy car until further notice! Watch this space.

[CTScott]

The Toyota dealer has just phoned me - the new alternator has been fitted and it has NOT cured the problem!
They have told me to keep the courtesy car until further notice! Watch this space.

They didn't per chance verify if your non-A/C Yaris has or doesn't have an AC Amplifier? Based on the European service manual section and EWD, it looks like it does, but based on your looking around and the Electronic Parts Catalog it looks like it doesn't. If it really does, then that is definitely the problem.

[motoxxx3]

They have not verified regarding the a/c amplifier as yet. When I mentioned it the service manager did not think my Yaris has this component.
I can tell you they have changed to date: Rheostat, blower motor, relay & alternator.
Iam quickly losing my faith in Toyota. They have had the car now in total 11 days, had a specialist engineer out from Toyota G.B. and they still can't fix it.
They told me the alternator is fluctuating output, dropping below 12 volts at times.

[motoxxx3]

Just had a call from the dealer - they have found a bad earth. Apparently it is now fixed!
Let's see if they have!

[CTScott]

Just had a call from the dealer - they have found a bad earth. Apparently it is now fixed!
Let's see if they have!

That sounds plausible. With it happening under load, I would believe that a bad ground could cause that.

[motoxxx3]

Latest update:
They have today fitted an auxillary earth strap from the blower motor to the car.
The reason being that they now think there is a fault with the earth wire in the car's multiplex wiring harness and by doing this is it will prove whether this is the case.
(They have changed every other component in the system)
I have to run the car for a few weeks and see if this has cured the problem.
Everything is checking out o.k. now with the voltage.
If this turns out to be the problem they are going to fit a complete new wiring harness.

[motoxxx3]

That sounds plausible. With it happening under load, I would believe that a bad ground could cause that.

Latest update:
They have today fitted an auxillary earth strap from the blower motor to the car.
The reason being that they now think there is a fault with the earth wire in the car's multiplex wiring harness and by doing this is it will prove whether this is the case.
(They have changed every other component in the system)
I have to run the car for a few weeks and see if this has cured the problem.
Everything is checking out o.k. now with the voltage.
If this turns out to be the problem they are going to fit a complete new wiring harness.

[motoxxx3]

The temporary earth strap has not cured the fault. It is doing it as bad as ever - on top of this I noticed a kind of 'plasticy' burning smell when I first started the car this morning.
Iam a very unhappy Toyota customer.
Back to the dealer on Monday - my patience has just about run out

[why?]

really sounds like you got the 1 in a million lemon. Sorry to hear about that. Hope they figure it out or replace it.

[motoxxx3]

After taking legal advice my car is back in at Toyota - Iam not happy - 5 attempts to fix it and still have the problem! they have assured me that this time the the car will not be given back to me until this fault is 100% fixed. Watch this space!

[pspeezy]

dang thats a bummer to hear, hope everything turns out okay.

[motoxxx3]

Final post.
Toyota have had my car for 4 weeks in total. Changed every component in the system.
It has now transpired that this is an inherent characteristic of the Yaris T2 1.0 model 06-10 without aircon.
Not just my car does this - all of this particular model Yaris' do it - and I have witnessed this now on other cars like mine.
So there we go folks, Toyota don't know what their own cars do, or why they do it, or if it is even actually a fault.
Turns out mine wasn't the 1 in a million lemon after all....just one of a bunch of lemons.
Back to a Honda next time.....probably.

[CTScott]

That is really strange, and one reason that I am glad that here in the US we get Japanese made Yaris instead of French made ones.

It basically means that the voltage is significantly sagging, but stepping on the accelerator normally has the opposite effect - It should raise the voltage, as the alternator should have a greater output at higher RPMs.

When you are driving at night, do you notice that your headlights dim when you step on the accelerator?

[motoxxx3]

No the headlights and all dashboard lights do not dim. However the interior lamp does dim in sync with the blower speed slowing down.
The tech told me the ECU sends a signal to boost alternator output when the lights are turned on, but it does not send a signal when the blower is turned on. This explains why the problem does not occur when the lights are turned on.
I have myself now checked a couple of 1.0 T2 Yaris and they do it also.
The 1.0 & 1.33 TR versions WITH aircon do not do it.
I totally agree with your comment about the Japanese built Yaris. They are sure to be better quality. The French built ones we have in Europe have VALEO electronics, which have a bad reputation. The Jap ones probably have Hitachi, Denso or Toshiba electronics.