98 S70 GLT Temp control is finicky

ferocity02 · Post by **ferocity02** » 27 Oct 2014, 18:13

Noticed this issue several months ago. The driver's side temp control acts very strange. It seems to randomly switch to full heat all on its own, even with the knob set on not full heat. When this happens, sometimes I can turn the knob one click in either direction and it will start putting out the correct temperature of air. The passenger side temp control seems to be working fine.

Occasionally when I start the car the orange lights on the HVAC control using will flash, indicating a fault with the system. I suppose these may be related. Perhaps a faulty blend door?

Car is a 1998 S70 GLT 2.4L turbo with 184K miles.

Post by **FlyingVolvo** » 27 Oct 2014, 18:57

Mine does the exaaaaaact same thing, so I'm just going to add to the pot of symptoms to hopefully help solve this.

Full cold = cold.
Full hot = hot.
72 = nice warm mix of air for a few minutes, randomly goes to full hot after a while.
Exact same thing, where I can adjust the temp by a couple clicks, I hear things moving and it blows correctly for a short period before either getting too hot or too cold. It's random, but tends to err on the side of being hot.

As far as settings, I never use the AUT. I always keep the blower in manual control and use the front dashboard vents, full open.

I've never really bothered to look for an answer I think, because I'm assuming it means some serious surgery to fix damper motors etc...

ferocity02 · Post by **ferocity02** » 27 Oct 2014, 21:23

Thanks for adding your experience. Do your HVAC lights blink when you start the car?

For the most part, when mine is on full cold it blows out full hot instead. One click from full cold then it usually blows cold and eventually goes hot. Or sometimes just stays hot. It seems to be almost completely random.

Post by **N_D** » 28 Oct 2014, 12:22

My HVAC lights were flashing and I had no idea what it was, the climate control didn't seem very responsive either. I eventually replaced the temperature sensor in the dash. Problem solved. The little fan on the back had seized up with dust and hair which caused the hvac lights to blink. Been working good since. The sensor can be accessed if you pull out the hvac controls and reach behind the dash.

Post by **FlyingVolvo** » 28 Oct 2014, 15:16

I've got the flashing lights as well. I used compressed air to blow out the fan, but it's possible it may have just died. Where did you buy your replacement?

Post by **N_D** » 28 Oct 2014, 15:27

I pulled it put of a scrap car at the wreckers, cost me $5. Ipd has new ones for something like $150.

ferocity02 · Post by **ferocity02** » 29 Oct 2014, 22:57

What little fan are you talking about? The blower fan, or a fan on the back of the HVAC head unit?

Also, is there a way to test the temperature sensor? If it's faulty it would certainly make for some incorrect temp control, but I would have thought that it would get stuck on either full cold or hot.

ferocity02 · Post by **ferocity02** » 09 Nov 2015, 22:14

Finally was able to get the codes from the ECC using Vol-FCR...

ECC-316: Recirculation damper motor, no position change
ECC-141: Passenger compartment temp selector left, signal faulty
ECC-414: Fan motor pass comp temp sensor, faulty signal
ECC-135: Engine coolant temperature (ECT), signal missing
ECC-124: Passenger compartment temperature sensor signal high
ECC-413: Fan motor pass comp temp sensor, Signal too high

I cleared the codes just in case some of these were stored from the last time I did some HVAC work. I'm going to rescan in a few days and see if any of these come back.

Post by **scot850** » 09 Nov 2015, 23:16

Sorry for the poor picture quality, but the cabin temp control looks like this:

: Cabin temp controller (1)

: Cabin temp controller (2)

Careful when removing this unit from behind the dash, as having been there for some time the rubber front cap tends to stick to the rear of the locating hole and then fall down behind the dash.

Remove the rubber cap and then you can see the fan blades and the temperature pin head on 2 wires.

Clean the unit carefully with IPA (rubbing alcohol) and cotton buds and a small artists brush. Finally squirt a little silicon oil at the base of the fan blades.

To remove from behind the dash, you need to push in the 2 'lugs/ears' on either side at the front of the unit. One is at 2pm and the other at 8pm when viewed from the front of the dash.

Neil

ferocity02 · Post by **ferocity02** » 09 Nov 2015, 23:20

Neil, I've replaced that temp sensor unit. I took mine out to clean and ended up breaking it, so I bought a replacement and confirmed it was working when I installed it. This was about a year ago.