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98 V70:Cabin Blower Speed Vehicle Speed Sensitive? Topic is solved

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sleddriver
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98 V70:Cabin Blower Speed Vehicle Speed Sensitive?

Post by sleddriver »

Someone explain this to me.....

Ambient air temp around here has quickly dropped from mid-80's during the day to presently, 57°F. This evening, I set the air temp knob to 80° to get some warm air moving around after the warmed-up-car sat for an hour and a half. At 0mph, the fan speed is whatever I set it at. As I slowly increase speed, it slowly drops. Past 20mph, the fan is barely on. When I pull up to a red light, fan speed slowly increases and at full stop, it's back on my previous setting.

If I set temp to 100% HOT, then the blower speed remains whatever I set, regardless of car speed. Problem is 100% HOT gets TOO hot after awhile.

So what's going on here?

My original ECC didn't do this. The current ECC was picked from a PNP after the original one "lost its head".

This is the first time I'm experiencing cabin blower speed based upon vehicle speed! I didn't even realize the ECC was capable of this! Very odd.....please advise.
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Re: 98 V70:Cabin Blower Speed Vehicle Speed Sensitive?

Post by scot850 »

Cabin fan motor bearings are failing. Time to replace it. You may get away for a short time with removing and oiling the bearings with light oil, but when the symptoms are as you describe it is not long for this earth.

Neil.
2000 V70 R - still being an endless PITA
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Re: 98 V70:Cabin Blower Speed Vehicle Speed Sensitive?

Post by sleddriver »

I don't agree as the blower motor was replaced earlier this year with a new unit. Second, doesn't explain why it will maintain constant air output when either on 100% cold or HOT.
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Re: 98 V70:Cabin Blower Speed Vehicle Speed Sensitive?

Post by misha »

scot850 wrote:Cabin fan motor bearings are failing. Time to replace it. You may get away for a short time with removing and oiling the bearings with light oil, but when the symptoms are as you describe it is not long for this earth.

Neil.
When they start going bad they usually start to squeal and make noise,like every bad bearing.When ECC sense just a hair of bigger resistance in fan motor,it will flash and turn the motor OFF immediately.You can turn it On & Off a hundred times and it will act the same...it will NOT turn the motor ON and if it turn it on it will cut it off in a seconds.

After the bearings are properly soaked with oil(engine oil is ok),inside and outside....they will work for years and will work like new.ECC will be happy and will allow the motor to work normally.I usually use a little syringe with needle for bearing greasing and for internal bearings i use extension sleeve from wd-40 spray which i put onto needle.
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Re: 98 V70:Cabin Blower Speed Vehicle Speed Sensitive?

Post by scot850 »

What you describe is a bad heater fan motor. When you accelerate, the fan cage moves back toward the rear of the car loading up the bearings and making it bind on the bearings. When you slow down, the fan cage moves forward off the bearings and motor speeds up.

What brand of motor did you use? Try the lube method misha recommends and I'd be happy to proven wrong.

The only 4 other parts that have an effect on the operation of the heater system are:

1) An air inlet temp sensor just before the resistor unit to the right of the motor. Never had one go bad. It measures the input temp of the cold air for the ECC to adjust the output temp from.
2) The resistor unit. This takes a signal from the ECC and temp unit to adjust the motor speed of the fan. These go bad, but typically the speed goes to one setting or stops completely when it fails
3) The cabin temp sensor. Have you ever cleaned that? It also has a little fan unit in it that pulls the cabin temp through it and measures the temp so it regulates the cabin. That sits behind a little grill to the left of the ECC unit. You have to remove the ECC unit to get to it. I have written up how to do that in the past. Careful when removing the sensor as it has a rubber boot behind the dash that likes to stich with age and then drop down behind the center console. These do fail as the fan unit in the sensor plugs up with hair and other gross stuff in the air and it prevents the ECC from adjusting the temperature correctly. Again failure of this does not cause the issue you are talking about
4) The ECC unit itself. I suppose anything is possible, but never heard of it being affected by vehicle speed as it is an electronic unit.

That is why I go back to the fan motor as the issue you are experiencing, and that I have had items 2)-4) fail over the years and only the fan unit causes this problem.

Neil.
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Re: 98 V70:Cabin Blower Speed Vehicle Speed Sensitive?

Post by sleddriver »

One problem with your explanation is that the blower fan speed will remain constant, whether at a stop or moving, when the temp control is either at 100% Hot or Cold, as previously stated. It only exhibits this odd variable speed blower sympton when the temp controls are other than the above. If it WAS a mechanical blower motor problem, it would rise/fall consistently, regardless of the temp setting.

Note when fan speed is set to AUTO, the ECC can & will vary the fan speed via PWM, and feedback from the cabin & air temp sensors, as that is the function of AUTO. Perhaps it's in the switch then?

Also note when I previously mentioned "vehicle speed", I was referring to an electronic signal being received by the ECC. Your above reply indicates you're focusing on the MECHANICAL movement of the car itself, causing a worn blower motor shaft to physically move back and forth. That's not happening here.

The cabin air temp sensor was replaced with a PNP. I verified its operation and cleaned it before installation. I also cleaned the temp sensor near the motor controller (ie resistor) when replacing the blower motor.

As variable temp is being utilized, it would point to a fault within that ckt.

Enable more head-scratching.......
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Re: 98 V70:Cabin Blower Speed Vehicle Speed Sensitive?

Post by JRL »

Are you using manual or auto mode?
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Re: 98 V70:Cabin Blower Speed Vehicle Speed Sensitive?

Post by sleddriver »

Manual.
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Re: 98 V70:Cabin Blower Speed Vehicle Speed Sensitive?

Post by BEJinFbk »

If you're running in manual mode, the fan should stick at whatever speed you set on the slider.
The speed signal from the car only affects the ECC's operation when in AUTO mode, AFAIK.

That said, the PWM fan speed signal (while in manual} is produced by the ECC based on the slider
position and sent to the fan speed controller mounted in the duct net to the fan. That tells the
transistorized module how it should modulate the ground it shows the fan motor. It shouldn't change.

Since the ECC was the last thing you messed with, it's probably worth running down a known good
ECC unit and swapping it in for testing. If that's not practical, start from the blower and work back.

So - What a guy could do to bypass all the electronics and check the motor is unplug the speed
controller, ground the (-) side of the blower motor, and it should run full tilt boogie whenever the
key is on. Drive it around and see if your blower is OK. If it remains stable, the speed controller or
overheated connectors at the motor and/or speed controller are worth having a look at. And don't
neglect the ground for the speed controller. If that "supply" ground is loose, it could cause the
problem you describe. Long shot, but worth checking out.

From there, you're kinda back to swapping out the ECC with a known good unit...
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Re: 98 V70:Cabin Blower Speed Vehicle Speed Sensitive?

Post by sleddriver »

I experimented some more with this odd pecularity last night. At 0 mph, manual fan speed is whatever I set it to on the slider. At 5 mph, it begins to decrease. At 10, decreases even more. Same with 15. At >= 20mph, fan speed is greatly dimished. As I slow down, it works in reverse. Very odd that.

I'll need to repeat with the temp set to say 74°F on both drvr/pass. knobs, fan set to AUTO and see what happens as I drive to & fro. See if the ECC is capable of adjusting both air flow & hot/cold supply to approach the temp. set via the knobs, then hold it there.

No amber lights flashing, but there still could be a code stored internally. Also could be something FUBAR with this ECC pulled from the junk yard. Could also be a problem with the cabin temp sensor, as it was also pulled from the yard. I may unplug it and see what happens. Then insert a resistor in its place for another test.
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