Help! Heater blowing cold air
Thread Starter
Burning Brakes
Joined: Aug 2000
Posts: 1,143
Likes: 0
From: Charlotte NC
Help! Heater blowing cold air
95 blows cold air when the heater is set to hot. Bleeding air from the cooling system did not improve the situation. Any suggestions on a fix will be greatfully appreciated. Thanks in advance.
Racer
Joined: Jul 2001
Posts: 346
Likes: 0
From: southwestern Michigan USA
Re: Help! Heater blowing cold air (Fang S-289)
probably your thermostat is shot. usually if the heater core is gone you would have a residue on your windshield. and if its the water pump you would have water leaking and/or a squeal...so, probably the thermostat.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Re: Help! Heater blowing cold air (Fang S-289)
Do check your operating temps. Could be a plugged heater core. The passages aren't that big and if plugged, coolant will flow from the inlet to the outlet, but not through the core. To check further, feel both the inlet and outlet hoses. If both are hot, then coolant is getting to the core, but probably not through it. Having the system flushed might cure it. Also you can try flushing the core by disconnecting the inlet and outlet hoses at the engine and running water through it. You can also try blowing compressed air through it, but go easy on the pressure. If you are changing and flushing coolant on a regular basis, but the coolant is cruddy, now's a good time to find out why. Have the system pressure tested for leaks.
Thread Starter
Burning Brakes
Joined: Aug 2000
Posts: 1,143
Likes: 0
From: Charlotte NC
Re: Help! Heater blowing cold air (SunCr)
SunCr, I think you've nailed it. Operating temp is normal. I should've noted that in my original post. Both hoses are hot, so I think you're right about the core being blocked. I'll try flushing it tomorrow. Thanks for the advice. :D
Le Mans Master
Joined: May 2000
Posts: 7,009
Likes: 0
From: Ideaology is a straight jacket for the mind
St. Jude Donor '06-'07-'08-'09-'10
Re: Help! Heater blowing cold air (Fang S-289)
If that doesn't work, check the heat exchange valve. My car had similiar symptoms. Replaced heat exchange valve. solved my problem.
Le Mans Master
Joined: Jul 2001
Posts: 8,183
Likes: 3
From: Santa Maria, CA
Re: Help! Heater blowing cold air (Fang S-289)
This is a common problem on our cars. Well maybe not common, but happens more than it should. I know mine doesn't work. There is a controller (vaccuum signal) on the interior firewall next to the steering column (on my 89 anyways) that might be a culprit. Check to see if the little door is getting vaccuum. Can you see it move open when you switch on the climate control? Cold weather is coming so I have to tear into mine pretty soon here.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Re: Help! Heater blowing cold air (89 Paul in cal)
As pointed out, another thing to check if your System is set up that way (I don't know). On an '89 the device on the driver's side is the A/C Programmer (Electronic Air) and that controls vacuum to all of the doors in the system. The door on the passenger's side controls flow into or around the Evaporator. Easiest to check by pulling the Blower Module from the Evaporator Housing on the Firewall and then going from full hot to full cold at the dash to see if it moves. At Full Hot you should see that no air can get to the Evaporator; hence, everything is going to the Heater Core. If the door doesn't move, something is broken. However, what generally happens when these things break is that you get cool air, then warm while using the A/C. Again, I don't know if your Model Year is set up this way, so perhaps someone with a Late Model C4 can chime in.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Re: Help! Heater blowing cold air (SunCr)
If you have the C68 electronic Climate Control, try disconnecting the battery. A friend's 90 ZR1 just had this happen and everything works just fine after doing this.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
