I just got a new blower motor and have heat/AC for the first time. But the heat doesn't come out anywhere near what I would call "heat". The engine just doesn't seem to heat up enough when the blower is on to produce heat. The thermostat was replaced a year ago with whatever was stock (180?) so I know that's ok. I did just replace the radiator and flush the crap out of it at the end of summer so it's been running much cooler since then as it is. I know the radiator fans aren't running, I have that on a switch I control in the car. It definetely will switch from hot to cold, the AC blows COOOOLD. What should I look at tinkering with here?

 

What is your indicated engine temp?

Are both lines to the heater core hot to touch when in Heat mode?
The heater core may be blocked ?

 

I haven't seen the temp above the second line with the blower running. I'll have to check the lines. And the integrity of the housing for the motor, maybe I'm just getting cold air leaking into it? Thanks for the start, I'll check that out.

 

I've seen this with quite a few cars over the years, especially if the cooling system was not well maintained. The heater core starts to get blocked up with.... snot, basically. Degraded coolant.

Take the heater core lines off at the engine or the heater core bypass assembly, whichever your car has. NOT off the heater core- you can easily break the heater core hose nipples getting the hoses on and off of them. Then take a garden hose, no sprayer on the end, and flush water through the heater core BACKWARDS of it's normal flow. Just jam to garden hose against the end of the (return-side) heater core hose and seal it up with your hand the best you can. What flows out the other (input heater core hose) will look pretty nasty, if I'm right. Then flush it through with the garden hose a couple times in each direction until it flows clean both ways.

On a later 3rd gen the "return" heater core line is the one that goes back to the hose nipple on the pass. end tank of the radiator, FYI. The "feed" line is off the engine and should have a vacuum-actuated bypass valve in it.

Done. You have full heat again. Remember to fill the cooling system back up with fresh mix when you put it all back together.

 

You could try pinching off the upper rad hose & see if the heat gets better, it goes without saying that you shouldn't drive it with that hose pinched off. If you get heat then replace the t stat with a 195* (stock) t-stat.

 

I've been trying different things since it seems temperamental, I did get some lukewarm air blowing out when idling at about 220* before I flipped the fan on, and I've also gotten some decently warm air when temp was indicated much cooler, but it never stays that way. So you're suggesting a backflush? Or is that something different? I only ask because my T stat ws called into question, but since it warms up nice and still no heat, that can't be it. Either way, I will do this and report back, sounds like the most likely culprit so thank you.

 

replaced the heater control valve and flushed the heater lines. Found a piece of plastic in the neck of the radiator that comes off the heater hoses that was blocking flow from the core to the radiator. Had the same issue as you do. I would check all the ports and hoses for clogging.

 

when you did this flush, did you have your heater on high (hot) to circulate the coolant thru there as well? you may have an air pocket in your heater core and until it's "purged" or bled out, you'll never get heat. had this happen to me before with my truck (was the victim of someone else's maintenance)

 

That is a damn good idea! I wasn't running it since my blower was shot at the time. Would it sound more likely the culprit if I said that I let the engine temp hit about 240 one night and since then I *sometimes* get heat?

 

the blower working or not shouldn't have an effect on it, cuz obviously it only controls the airflow. the temp control needs to be on high in order to allow the valve to open and circulate the coolant thru the core.

the knucklehead who had my truck before apparently didn't know to turn on the heat when doing a coolant change so there was always that air pocket in there. he even changed the control panel (used one with no rear defrost function, too) and must have given up. when i got the truck, there was only two temps - cold and hot. soon as i even started to go to hot, it was straight-up hot, no in-between, so very frustrating trying to adjust the temp. i put the right control panel in, had it tested before-hand, but still no joy and i just had to deal with it. then one day it just wasn't getting hot (like yours) and i had the system serviced and everything works as it should now - including the temp control. i would have never known otherwise, had it not quit getting hot, but this is some of thee issues that can be inherited with a used vehicle... but i will also say that if i had to choose changing a heater core in my truck or my Z28, i'd do the Z28 anyday...

good luck - i hope purging and filling the sytem takes care of it

 

Looking like I need to blow it out or maybe flush the core itself again. It was staying pretty hot but now it only does when it wants to again. Floor heater seems to work slightly better than vents for some reason. This is becoming very annoying.

 

i have that similar issue with mine, but have not had the time to work on it. it seems to have better airflow out the heat ducts than the vent or defrost. i assume for now that that issue is related to a "duct door" malfunction, such as the vacuum on it... not sure. but it would really suck to have to replace any of those actuators behind the dash.