1998 S70 T5A, Not your typical blower motor issue

[Burn-E]

I'm opening a new thread here because all I'm doing is talking to myself over on Volvospeed.

http://volvospeed.com/vs_forum/topic/16 ... 8-s70-t5a/

Here's the deal:

So I've been encountering some erratic behavior from the blower in my 1998 S70 T5A and trying to figure what is causing it. I don't recall experiencing this with any of my other P80's.

I've swapped out the ECC, the power stage and the blower motor for known good functioning units. Symptom continues.

Symptoms:
Blower motor slows down or even cuts off once the car accelerates to 30-40 MPH / ~2000 RPM.
Once the car slows to below 1000 RPM the fan starts to spin back up and comes to full speed once the car comes to a complete stop. The fan still blows some air so it's not completely off - usually.

I'm fully aware that the AC and the blower motor spins down with acceleration and as the car goes into boost - but the AC is not on in this scenario.

Settings when this happens:
1. Set the ECC fan switch to full (all the way to the right) or to Auto (all the way to left) - really any setting besides 0 but it's most noticeable when the blower is running full.

2. Set the temp switch for both driver and passenger side to anything above cold (blue) and below hot (red).

3. Set air circulation to outside air

Settings when this doesn't happen:
1. When temp switch is to cold (turned 6 o'clock to the blue) or hot (turned 12 o'clock to red)
or
2. When air circulation is set to recirculate internal air

Is this normal behavior? Have I just not been paying attention previously? I usually keep the ECC set to outside air, 68 degrees, auto fan. Temp gauge in the instrument cluster is sitting right above 3 o'clock where it should be.

My guess at this point is if it's not normal behavior then it's related to a temp sensor like the thermostat, an internal temp sensor is malfunctioning, or there's an incorrect signal coming from the speed signal impulse sensor.

Here's what the ECC climate control, AC & Heater Service manual states:

If fan speed control lever is set to AUT (automatic) mode, fan speed is influenced by the position of drivers side temperature control dial, drivers side interior temperature sensor, vehicle speed, and engine coolant temperature.

The highest fan speed is selected if drivers side temperature control dial is set to maximum or minimum cooling or heating. The greater the difference between the desired and actual temperatures, as sensed by the drivers side temperature sensor, the higher the fan speed.

As vehicle speed increases, the fan speed will be reduced to maintain a constant airflow throughout the passenger compartment. When heating the passenger compartment after starting a cold engine, the fan speed is gradually increased as engine coolant temperature rises.

But I don't recall it ever being the case where setting the temp to say 70 degrees when it's 50 degrees outside and the car is already warmed up (thermostat gauge at 3 o'clock) with the fan set to full power (all the way to the right) and the blower motor essentially shutting down once I start accelerating and then turning back on to full blast when I come to a stop.

What am I missing here? Does anyone else experience this?

[z2003]

ECC should have ECU control. did you try to check the code?

[taxi]

Hi!
I can only say, something is wrong. With the blower on maximum speed it should stay there.
One more thing comes to mind: the way the blower is mounted could make it sensitive for the acceleration of the car if the blower motor is worn. The thing that comes to mind is my previous blower's squeak before it broke. I could decide how much squeak I wanted by breaking and turning..

[jblackburn]

I have never noticed it on anything other than 'auto' fan speed. Set mine to full, and it stays there no matter how hard you stomp on it.

Is your serpentine belt slipping or has the tensioner failed?

I might also check grounds - by the passenger side headlight and by the battery itself.

[Burn-E]

Thanks to all of you, this is primarily what I was looking to confirm - is something that sends a signal to the blower malfunctioning and where else I should look. Because I've definitely tackled the usual culprits and none of them have fixed the problem. And you've confirmed I'm not crazy, there's definitely something wrong.

I'll check the serpentine belt and the grounds and see what I find.

This car only has 63k miles on it so we're still dealing with relatively new components as far as wear and tear go but the parts are still 15 years old.

[LakeFlambeau]

I am seeing similar things with my 1998 V70XC. A search popped up this thread.
So, I am looking for an answer myself.
I have another 1998 V70XC that I just had the fan motor die on this summer, but
do not remember the symptoms being like this.
Sorry I am not of any help, other than confirming similar symptoms.

[LakeFlambeau]

An update on my blower motor issue. I was seeing the changing of speed, as stated above.
It kept getting worse. Finally the fan would not start. I could bang the dash just
below the glove box, and the fan would start and still vary in speed.
It is cold in Minnesota now, so I gave up and just installed a new blower.
New one works perfectly, with no change of speeds.
It is a easy fix, if follow the directions in the video I found on youtube.

[madspeed50]

easy to replace for sure. Mine was doing the same, i was able to find a low mileage unit with a date code of 2009, so should last a whle

[tdietz]

Found this forum when searching for a similar issue on my 1998 V70 GLT. Regardless of the position of the blower speed selector, the blower will go haywire on startup... it'll blast, stall, blast again, and finally regulate to whatever setting it "should" be on. I cleaned the connectors to the resistor and blower, and now it does it less frequently. I'll call that a success.

Here's where it gets weird - When it's hot out and the A/C is on, occasionally the passenger side will start blasting hot air. The only thing that mitigates this is turning on the floor vents, closing the dash vents, and waiting 2-5 minutes for it to switch back to "cool." When this happens, you get a nice coolant smell in the car. When blasting the heat, you get the same smell, but the opposite happens - the passenger side will randomly blast cold air for a couple of minutes.

I'm stumped. Any ideas?

[57gretsch]

Contamination of sensors from coolant leak in heater core?

Grounds are critical. If they are loose the smashing about may trigger them.