Just got the blower motor out the other day and weirdest thing happened. As I was pulling it out, it seemed stuck so by the time I got it out, it loosened up. I reconnected the plugs and was going to turn the ignition on to see if it was going to work. Well before I even had a chance to turn the ignition on, it started working. Good thing I didn't have my fingers near it! So I turned the ignition on and it stopped... I grabbed the unit and then it started working again. The plug housing on the back doesn't make a proper connection for some reason. Should it be working when the car is off also???

 

No it should not come on with the key off or you'll end up with a dead battery. I can't remember off the top of my head what causes it. Either a bad control head or a bad blower motor resistor.
Do you have the manual temperature control or the electronic control ??

Someone will jump in or you can do a search for that blower staying on.

 

Ok, I found a thread on another forum, read that and let us know if it helps...


http://volvospeed.com/vs_forum/topic...ys-on-for-850/

 

Oh I forgot to mention it's a 96 850 Turbo... I think its manual (just has dials for the temp setting, not led screens or buttons). If I remember right (have to double check) when I did turn the key on, the fan speed was actually controllable... When the car is off, it turns at one speed. Where is the BMR and ECC located???

 

My guess would be that you have a bad ignition. The fan should not be getting power with the key off.

 

How do I pull the plastic backer off the blower motor unit??? I pulled the little screw from the back out, but it just won't budge. I don't want to put too much pressure on it and then break with the fan or cap.

 

If it was a bad ignition, other things should be running also, right???

Okay so I tested it out again... It runs full speed no matter if the key is on or off and what position the fan speed control is in (auto, low, medium, high). I had a hard time trying to get it working this time around. The fan does turn a little harder than it should (my personal opinion) and there is dust from the bearings around the unit but there isn't any play in the bearings. The very first time I had it going, it did squeak a little at the start and now it doesn't anymore. Now when I bent the plug in a certain position, it works fine, so I'm thinking what ever is in behind the plastic cover is dirty. I would also like the take the plastic cover off to oil the rear bearing too. From what I've read, the fan can stay on from either a bad ECC or resistor block. I have unplugged all the wires around the unit before (assuming one was for the ECC) and it still continued to stay on. I'm wondering if the motor was turning harder, it put too much load on the resistor block, and then finally burnt it out.

And I tested for codes... Nothing comes up.

 

Bad ignition, other things running ..... not always. Take a look at all the contacts on the back of that switch. My switch was bad and it's because it would drop my cruise control here and there. Had no clue till I came across a couple different threads complaining of things an ignition switch can cause as it's starting to fail. Who would think the ignition switch could disengage your cruise and prevent it from resetting ?? NOT ME.

From what I remember you are right in that the ignition would cut the blower out but if the fault is a stuck control head or blower motor resistor it acts as if the ignition is on.

It's like a starter staying on because the solenoid is stuck on. It doesn't need the "keys" signal from the ignition. Same with the blower. The blower gets its main power through another circuit and is supposed to be switched on and off by the ignition but if there is a failure the blower can get the power without the switch being "on".

The fact that the key is off and the blower is running tells you you have a good blower, good fuses but a control head or resistor that has failed in the "On" position.

I'm sorry, it was late when I wrote the first reply or I would have tried to tie it to one of the threads on the problem.

Please let us know what you find.

 

I've been playing around with it today some more...

So I finally figured out how to pull apart the fan from the plastic housing and the terminals are definitely dirty. The brushes and armature is done though, so I do need a new fan. Now I have used contact cleaner on the ignition switch and I also unplugged it and I'm still getting constant power to the blower motor plug(I switched to a volt meter because I have the blower motor unit apart). I've also unplugged the control unit (I guess there is no resistor block because I have climate control) and there is still full voltage at the plug.

 

If you have the automatic temperature control or ECC unit it is the one with the dials that have the temperatures in degrees stamped on them then you do have a blower motor resistor. It is the more expensive of the two, around 200 bucks new and for some reason there is a different part number for a sedan than a wagon ??

If you unplugged the control head and still had power to the blower motor than it is the resistor that has failed and is powering the blower motor when the system is in the "OFF" position.

Blower Motor Stays On For 850 - FWD/AWD 1998 and Prior - Volvospeed Forums

 

Yep, it has the degrees stamped around the dials... Okay I think I'm falling behind on the electronics now lol. It probably doesn't help that my head is still stuck with the terminology from my other vehicle haha. That thing you posted a photo of with the aluminum fins is the control head (I called it the control unit) right??? That is what I unplugged... I assumed the ECC was a computer box under the dash, not the actually in dash hvac controls with the dials and switches.

 

The finned thing is the power module (or blower motor resistor) and should be bolted into the plenum to the left of the blower motor.
The "ECC" electronic climate control is the designation for this type of system but most refer to the "head" unit in the dash with the dials and blower speed slider switch as the ECC too.
If you're even close in terminology most of us can get it as I'm pretty sure most of us have been caught using some other manufacturers name for a part the Volvo engineers chose to call something else but has the same function

If you don't have this Volvo service manual please down load it, it's priceless.

http://www.matthewsvolvosite.com/for...pic.php?t=8018

Once you have it downloaded you need the forth file down, "AC heater system auto". That will have a diagram of the wiring.

 

Thank you for the manual

Oh, it has it's own separate diagnostic system that is different from the OBD2 test... So I didn't scan for codes. But I do remember when I first got the car running, the a/c and rec leds were flashing. I don't have the Volvo test unit though.

What I've unplugged from the system:
-power module
-passenger side temp sensor
-ignition switch
-damper control units
-some blue relay in front of the duct



So if I unplug the ECC and the blower does stop, will that mean the problem is within the ECC???

 

Picked up an ECC for $20 :P Well that wasn't the problem, so I have a super cheap spare which is good... Teared the wood grain off and it was pretty bad so I threw it out. I'll replace it with new stuff hopefully.



So it's got to be the power stage unit then, right???

 

Bumping back on my old thread here... Just finished school, so now I finally have time to trouble shoot this thing over again. So I checked out it does have a fuse under the hood, pulled it, and there is still power going to the blower motor plug regardless if the power stage unit is attached or not.

I really hate buying a new part that costs me $150 and finding out it's not the problem. And I can't exactly find them used either.

 

Just to stay on the same page, when you say ECC are you talking about the unit in the dash ??

 

Yup with the control temperature and fan speed dials.

 

Still having the problems... Ordered my parts and just got it yesterday. Installed the new power stage unit and the new fan and it's still on with the key off.



Any ideas... Now I'm thinking it's a relay. What relays control the hvac system and where are they located???

 

I put together a picture video on "How to remove and lube the blower motor fan on a Volvo 850". Hope it's useful to someone.