1999 V70XC HVAC fan with a mind of it's own

[Frogerelli]

Good afternoon,

My A/C still puts out cold air and the heater still warms, but the fan speed fluctuates constantly and never reaches max output.

I presume the temperature sensor must have something to do with it, but I don't know how much fun that is to replace or it that will solve the problem entirely.

Thoughts?

[erikv11]

I'm assuming this car has ECC (Electronic Climate Control)?

If it works like on the 98 and earlier cars, then the fan speed is controlled by something called a power stage, also referred to as a blower motor resistor. It sounds like it has gone bad.

[Frogerelli]

Yes, it has electronic climate control. Do you have any details on the resistor, such as where it is located (dash or on the motor)?

[erikv11]

It is under the dash, you will have to pull the glove box to get to it.

Here is a picture of it; the big metal fins are in the ductwork so you can't see them until you pull it out.

https://www.fcpeuro.com/products/volvo- ... 70-9166694

[erikv11]

This is an expensive part, I am replacing one this weekend on a 98 using a junkyard part. Hopefully it will last a few years ...

[erikv11]

Check out these posts, good info:

https://www.matthewsvolvosite.com/forums ... =1&t=53024
https://www.matthewsvolvosite.com/forums ... =1&t=56904

I think I would check out the contacts first, unusual for the resistor to be intermittent.

[scot850]

Also take out and clean the temp sensor. IT sits behind a small grill to the left of the ECC on the end of the line of switches running from the steering wheel to the ECC unit. You have to pull the radio, and the ECC unit (takes about 2 minutes, but make sure you have the radio code!!).

Volvo radio and ECC unit

Temp controller grill in facia

Radio retaining clips

If you have the Volvo radio, there are 2 retainers you push in to release the radio. The are near the bottom of the sides of the radio. Push them in and they pop out, pull gently on them and the radio comes out. Disconnect the various cables from the rear and remove the radio unit. Push up on the bottom of the ECC unit from its rear and underneath. It can be reluctant to move but it will come out. I wear gloves for this as there can be some sharp edges in there. Again undo the cables from the back and remove the ECC. Pushing up helps depress the top 2 retaining clips making it easier to push out.

ECC unit removed

ECC unit and view of 2 top retaining tabs. 2 below also

Rear of ECC unit and 2 cable connectors

You need to prise out the last switch unit to the left of the little grill and disconnect it. This gives better access to the cabin temp controller. If you use a torch, and look into the left of the hole left by the ECC unit, you will see the cable that connects to the end of the cabin temp controller. Remove the cable.

Rear of cabin temp controller

Temp controller left side with lower left tab

Now the fiddly/PITA part, removing the cabin temp sensor. There are 2 'buttons' you have to compress toward the front of the unit. The upper on is at about the 2 o'clock position looking from the front, and the other at around the 8 o'clock position. The 2 o'clock one is easier to access (relative) so push it in (they can be tight) and gently lower the rear of the unit to loosen it. Then tackle the other one. This is where removing the switch to the left can help give access. It is a pain, but take your time and don't break it!! There is a rubber ring on the front face of the unit that acts as a seal to the facia. Make sure that has come out with the unit. Carefully clean the unit with cotton buds and rubbing alcohol. If you have compressed air, gently fire some air in the side of the unit to make sure the little fan moves ok. I give the fan unit a little silicon oil lube to make sure it moves good.

Temp controller orientated as I remember!?

You can reconnect the temp sensor cable but don't install it. Also connect the ECC unit and sit it in the radio hole. Switch on the ignition, and see if the little fan moves ok, and move the controls on the ECC unit to see if that fixes the problem. I find the sensor tends to only really affect the fan speed in AUTO mode. If the fan works ok in the manual speed adjust, but not in AUTO this is likely the culprit. Others may disagree. When these fail they do throw a code (don't know what that is though).

If not, it doesn't mean the unit is good, but before spending money (unless you want to chance one from a breaker yard (I paid $10 each for 2 from a pick-n-pull). and then tackle the resistor pack.

The resistor pack may not be the issue though. It could be the fan motor is binding up. It is a little tricky to remove, but you could try doing that and give it a little lube to the bearings to see if that helps.

Neil.

[Thunderbox]

here's a little trick I tried recently with my ECC and weird fan issues. I pulled the ECC and sprayed it on the inside with Quick Drying Electrical Contact cleaner. CRC makes a good one. I paid attention to the slide switch for the fan speed. I suspect that the contacts in the slide get dirty or corroded. It seems to have fix my fan control issues for now. Good luck.

[RigsPGT]

i've had similar issue before and after replacing the fan motor, things came back to normal. I'd say take a trip to the JY and source one there as it might end up cheaper.