960 Jumping in on the heat issue bandwagon

Hey all - hopefully this is pretty simple but I figured I'd ask. This has been like this for the past three years - when ever it's below say 50 degrees, Cloud will take about 10 to 15 minutes to start blowing warm air in the cabin, and the water temp gauge will never reach half way. Last night when it was 29 out, it never got past a quarter the way up. I get luke warm air, but that just keeps the engine from warming up at all.

I had the heater core replaced about five years ago, so I don't think that's an issue. Dad thinks it's the coolant thermostat - which would be nice since that looks to be only $20 for the real Volvo part. What do you guys think?


EDIT: So I take there is a temperature sensor (reads temp) and a thermostat (controls flow of coolant) - would one of these be more likely than the other?

I've been having a similar issue. I'm also thinking its a thermostat.
Make sure to get the seals as well when buying the thermostat!

The thermostat is the most likely. If you had heat and no gauge function then sensor.

Make sure you have the system fully filled with coolant which can affect both.

If they put the 71 degree thermostat in there I doubt the heat would be very hot in the weather we are getting. A standard temp 88C should get things proper.

Thanks guys!! I’ll order a new thermostat and seals!

I should also add that last year I wired the flap in the air box open - the flap that lets in fresh air from the grille vs hot air off the exhaust manifold was no longer working and in the summer it needed fresh air so it’s more or less permanently wired open (for whatever reason the default position is closed). I know that’s not ideal and I’m sure it’s not helping, but that shouldn’t hurt too much should it? What I mean is - these low of temps is likely a coolant issue and not a fresh air issue?

On my 240, I noticed absolutely no difference with the preheat hose attached to the air box or not. Mind you, that is in Vancouver where it rarely drops below freezing.

If I had a car with poor heat the first thing I would suspect is a blend door. Not sure how it works on these cars, but I would research it and manually go in there and open valves/doors by hand and see if i could get warm air. I might also try stuff like pulling the heater hoses and blasting water thru there and see if it were restricted. Shouldn't be too hard to figure out.

dl242gt said:

If they put the 71 degree thermostat in there I doubt the heat would be very hot in the weather we are getting. A standard temp 88C should get things proper.

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Thanks, I'll look into that. I checked VADIS and it says my thermostat should start opening at 87C, and be fully open at 102C - so I guess it already has the one you're talking about?

ZVOLV said:

If I had a car with poor heat the first thing I would suspect is a blend door. Not sure how it works on these cars, but I would research it and manually go in there and open valves/doors by hand and see if i could get warm air. I might also try stuff like pulling the heater hoses and blasting water thru there and see if it were restricted. Shouldn't be too hard to figure out.

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Thanks, I'll check that out! I believe mine is on a servo and I believe I can hear it groaning as it opens and closes, but I'll take off the kick panel and see if it's working or not.

I know the auto climate control head on the 7 and 9 was somewhat common to fail. Intermittent points more towards electronics than a mechanical failure.

You are going to have to spend some time researching the electrical and vacuum schematics and figure out where the voltage or vacuum is going missing. A simple vac guage may help.

First thing i would check is not the heater core or climate control, If the engine shows cold, It is not a climate thing. My guess would be your cooling fan thermostat is not shutting off, and the fan is running too much, like all the time. The fan should not pull much air at all through the rad until the engine is warm. If it is pulling air like a hot august freeway drive, the car won't warm up.
This next trick shouldn't be needed until it is below freezing: Cover half your rad with cardboard. If it is running fine in the summer, and this cold snap is temporary, cardboard is king. Less air through rad=warmer car. In cold climates, they make snap on grill covers they call winter-fronts because NO car will warm up if it is -40 outside.

Vernet and Wahler make the oem thermostats. They both work fine. I think the vernet is 88C and the wahler is 87C but one degree isn't any real difference.

It's -23 F here today, just to put in perspective the hell I live in. So yeah over the years I've had some experience with heaters.
Number one first thing you figure out is the thermostat. You want that engine coolant at around 180 degrees, more if possible. Keep in mind the heater core is heating outside air so it's got to be warm. If you try to get smart and run the heater recirculating inside air the windows will fog up in short order. That's why they pull fresh air.
Some vehicles just don't run warm in that kind of cold no matter what you do. You'll freeze in a Geo Metro for instance.
Ok after that is the heater core plugged? Is it plumbed right? (sometimes the lines are just reversed) Does it use a valve to regulate coolant flow? Is that working? If it's a "blend door" is that working? Is the core plugged?
BUT over all that coolant temperature has to be hot first and foremost. And circulating through the core!

Odd ball things. Some engine have little tubes inside that rot away and cause poor circulation.
Very odd is the water pump impeller that's bad or fell off, normally that'll overheat the engine pretty fast too. Saw it happen once on a piece of logging equipment where the engine didn't overheat but operator was freezing at -30.

Sometimes, on some vehicles, you will need to cover the radiator, most often on newer ones you don't. Put 500,000 miles on an 88 F350 and one night at -50 I was really glad to see an empty case of beer sitting by the road !

Thanks for all the replies guys! I was going to order and do it myself, as it doesn't seem too hard at all, but since I don't have a back up car in case anything goes wrong, Dad suggested I just take it to our mechanic and he'll do it for me - he agreed it sounds like the thermostat might be stuck partially open, so he's going to replace it, the radiator hoses, and flush the whole system.

I'll report back next week to let you know how it goes!

Hey guys! Late reply, but I got the thermostat replaced and upper and lower radiator hoses replaced, as well as a coolant flush which my mechanic said was really clean still (no crud inside). He replaced the original 90C thermostat with a 92C.

Good news is it heats up great now! No longer takes 15 minutes for the engine to get even close to halfway and for warm air to start blowing; it's fully warm and starts blasting hot air in about 3 minutes or less

Nice nice nice. Start with the easy stuff, right?

Glad you are warm in the car. Enjoy.