1999 S80 heater blowing cold air

retcoastie · Post by **retcoastie** » 31 Oct 2011, 11:03

We have a 1999 S80 T6. Any position of climate controls results in cold air coming out of the vents instead of heat. The thermostat is good as the water hoses get very hot. The hoses going into and out of the heater core both get very hot. I flushed the heater core backwards and forwards several times with good clean water coming out with a decent flow. The electric duct doors on both sides of the air plenum move. I don't know which motor does what. I suspect an interior plenum door is not moving, allowing air to pass thru the heater core.

What should I check before tearing the entire dash apart to open the air plenum chamber?

Thanks

Ken

Post by **boosted5cyl** » 31 Oct 2011, 11:38

Does is ever get warm at all? For some reason, this year my S80 has decided to take a good 30mins before putting out warm air, despite the water temp gauge being smack bang in the middle for 20 of those.

I suspect an air door in my case too, but I dont know to be honest. Typical though, I got my AC working awesome for summer, now the heating is giving me guff LOL.

retcoastie · Post by **retcoastie** » 31 Oct 2011, 12:07

I don't know if it ever will change to hot air, but the normal 1 hour commute is cold!!!!!!

retcoastie · Post by **retcoastie** » 22 Nov 2011, 09:45

Checking the hoses and pipes did not find our problem. Both were very hot. After doing all the normal stuff, I accidentally touched the bottom of the heater core on the passenger side. It was cold while the pipes and hoses were hot. I removed the core and found that the plastic wall between the input and output chambers had disintegrated, allowing the hot water to enter and leave without passing through the tubes.

I snagged a life time warranty core for $27 with shipping on Ebay. Problem solved.

Post by **boosted5cyl** » 22 Nov 2011, 21:38

Thanks for posting back, that's interesting. Was it a big job to remove the core? My water/coolant temp gauge has been creeping one to two notches to the right as well as having intermittant cabin heat. Unless the air flaps move back to a "cold" position after the car has been stopped I can rule those out. Once it got warm (eventually) a couple of days ago ive left both temp dials at full heat. Sometimes its warm, sometimes its not. Complete luck of the draw it seems.
Wonder if the same thing happend with my core...... I'll keep everyone posted when (read if) I get a chance to check it out.

retcoastie · Post by **retcoastie** » 23 Nov 2011, 20:16

You're welcome.

No! The core was not as bad as I had expected and easier than some I have done. Now that I have done it once, I think it is probably less than an hour job. The main things that gave me problems were the aluminum tubes between the heater hoses and the core itself. The clips on the core required me to make a special tool to engage and pull them. The twist connectors on the firewall side gave me fits. I expected them to require a larger turn than is necessary to release them. I kept trying to turn the collars and nothing was happening. After getting one off I learned that it only takes about 1/8 inch of turn to cause the tabs to raise far enough to release the tubes.

Volvo says they have a special tool to remove the brake light switch and that most DIYers just break the switch and put in a new one. (Neat sales pitch) I used a mirror to look at the top of the switch holder. It looks just like what you see from the bottom. A carefully placed small screwdriver blade will push the tab down and allow the switch to be removed. I had trouble replacing the brake light switch because, laying on the floor looking at it upside down, I kept thinking that it went in level. After two or three trips in and out of the car (hard on an old back) I realized it is at an angle. Lowering the rear of the switch allowed it to go right back into the bracket. DUH!!!!

We do have a steady temp gauge reading. If your gauge is creeping you should really keep an eye on it. That could be an indication of a completely different problem. I have seen a couple Volvos with more than one problem at the same time.

Good Luck and lets us know how things go.

Ken

lotus4s · Post by **lotus4s** » 24 Nov 2011, 08:02

You're right on the switch, it comes out pretty easy when you release the tab on the top. Here's a pic.

BerniniCaCO3 · Post by **BerniniCaCO3** » 25 Nov 2011, 23:55

Cool! I'd never looked inside a heater core, and I had no idea there was just an internal plastic wall-- I am understanding you correctly, right?
I agree- heater cores are very easy on a volvo. There are some very frustrating design decisions, but the heater core is one of the smart ones.
On my old ford, I did have to remove the entire dash to do the heater core. Not so with volvo.

Those heater core hoses are one of the frustrating designs. I use a heavy right-angle pick, and pry the grey lock collar over to the open position. Sometimes I go with long, 45-degree pliers (where the tips of the pliers bend down).
You cannot reasonably get your fingers around the collar in the space provided, as I think maybe someone had intended with the ridges that are cast into the collar.
There are two plastic barbs that the collar forces back out. I did have one heater core where the barbs, having been forced out, did not spring back into locking position. Yes, I had the collar rotated all the way into the lock position. I had to get a new hose, no other way around it; it would have blown off once the system pressurized if I'd tried to use it. *sigh*.

A low coolant level can explain creeping temperature rise AND little heat from the heater core. But... these cars have low coolant indicators, so I presume you'd have seen that! But check your overflow bottle just to be sure.
A dealer should be able to quickly tell you if the air flap (blend door, controlled by a servo/ damper motor) is functioning correctly. The software (VIDA) lets you communicate with the climate controls, and it knows where the damper motor should be, and where it actually is, and if it's very far off something's wrong in the climate box.

retcoastie · Post by **retcoastie** » 26 Nov 2011, 06:44

Yes, you are reading correctly. The heater core has four rows of tubes. There is a serpentine wall separating them into two row chambers. That wall had a huge section missing. I could stick a soft wire into one hose opening and see it through the other opening.

Post by **Lynette** » 23 Jan 2016, 08:14

After replacing the heater core, cold air is still blowing. What should i look for?