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Old 10-30-2003, 12:57 AM   #1
Debbi's 94 coupe
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Member Since: Oct 2003
Location: Duncan BC
Default Heater blows cold air

I've only had my car for a couple weeks, and I've found out the heater won't blow warm air. OK, my coupe just came north from Arizona, so the heater was probably never used.

The car is set up with the automatic electronic climate control option with the temp set digitally. Can anyone suggest things to check out and/or ways to correct this condition. Is this a sympton of a thermostat problem... or potentially overheating of the engine.

This form is great. I got great help on my questions on DRLs for my import into canada.

:D
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Old 10-30-2003, 01:00 AM   #2
BAM92
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Location: Houston Texas
Default Re: Heater blows cold air (Debbi's 94 coupe)

Some people bypass their heater cores since it is easier than to replace it. Have to check hoses in engine compartment on passenger side leading into firewall that they are not blocked off and bypassed. Just one idea.
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Old 10-30-2003, 01:35 AM   #3
rodj
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Default Re: Heater blows cold air (BAM92)

Where the hoses (if connected ) go through the firewall there is a vac operated valve that controls the flow to the heater core.Check that this can be moved by hand(can get crudded up if not used).If so check to see if it changes position when you move the controls inside. Also posible vac leak/ no vac to control valve.
If the valve works or can be manually operated, both hoses should be hot with the engine warm.If so then hot water is getting to heater core , so possible problem with flaps / doors in the heater itself.Have not gone this far , others know the internals of heater better.
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Old 10-30-2003, 09:47 AM   #4
COMPVET
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Default Re: Heater blows cold air (Debbi's 94 coupe)

I agree with rodj, it is probably the water control vave if the plumbing has not been screwed with. They are prone to breaking up insde. Just because it apears to move on the outside does not mean the inside is moving. Like rodj said, check the pipes to see if they are hot. This will verify water flow
Pete
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Old 10-30-2003, 11:42 AM   #5
SunCr
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Default Re: Heater blows cold air (Debbi's 94 coupe)

No heater control valve on a '94. Verify the air door is working by removing the blower module from the evaporator housing and while someone operates the controls, make sure the door is moving. If the door moves and the core is hooked up, it may be plugged. Try flushing it by removing both hoses and connecting a garden hose to it. Flush the entire cooling system too; otherwise it may plug up again.
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Old 10-30-2003, 06:37 PM   #6
Mark-44
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Default Re: Heater blows cold air (Debbi's 94 coupe)

Welcome to the forum.

My suspicion is that the heater has been bypassed due to a leaking heater core. Check the hoses on passenger side frame rail just as they come from the radiator; that is a good place to install the $2.00 bypass hose connector.

Since you just bought the car -- perhaps there is a warranty. LOL.

Mark
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Old 10-30-2003, 07:39 PM   #7
Goody
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Default Re: Heater blows cold air (Mark-44)

:iagree: Gotta make sure it passes the "warm hose" test.
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Old 10-30-2003, 09:42 PM   #8
pablocruise
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Default Re: Heater blows cold air (Debbi's 94 coupe)

Welcome to the forum! Glad you could join. We need pics of your car! :D
OK,
it is possible to view trouble codes by way of the display panel on the HVAC unit itself. Click on this link for more info on that:
http://www.idavette.net/tech/c4diag.htm
I happen to feel it's poor vacuum signal from the engine. As mentioned above. The tubing gets brittle and breaks real easy. Vac leaks real common.
Now, if none of that works, you may have to dig alittle deeper.
Here is what you are trying to see thru the little opening when remove the controller in the engine bay(I know your 94 is probably different, but just trying to ballpark you)

Click the image to open in full size.
Click the image to open in full size.
in yellow, is a cheap plastic link that can possibly break. Can test by inserting a thin stick of some kind down in there and gently push back and forth on it. If it flaps loosly, broken link. If firm both back and forward, link good.
THEN, look into this scenario:
loosened solder connections on the circuit board (under the dash, on the firewall, next to the steering column) from heat

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
note: the above pictured circuit board is covered in a black plastic box.

Hey SunCr, we CA folks can't tell it's fall till all of these "no heat" hreads start popping up huh? And summer when the "No A/C" threads pop up.
How are you folks doing with the fire lines?


[Modified by 89 Paul in Cal, 6:46 PM 10/30/2003]
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Old 10-31-2003, 12:11 PM   #9
SunCr
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Default Re: Heater blows cold air (89 Paul in Cal)

I think a New Englander posted the first "no heat" topic of the Season at the end of September. I usually recommend a flush since that intially worked for me. A month later I was replacing the core and the biggest headache was keeping the glue from the plenum off of the carpet. After I got it out, I took the old one and ran hot water through it and though the top was hot, the core was ice cold. I then put 125 psi from my compressor into the outlet and with my thumb momentarily blocking the inlet, I finally got a loud pop from it when I removed my thumb. I reran hot water through it and verified that the entire core was getting hot and put it in my pile of spare parts.

Fire has moved East and it's now damp and I heard that the black cloud raining soot and ash over us on Tuesday had reached Vegas yesterday. Assuming another Santa Ana doesn't follow the cold front, things are looking better.
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Old 10-31-2003, 12:38 PM   #10
sothpaw2
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Default Re: Heater blows cold air (SunCr)

Why do the LT1 C4's have such poor heater core design? My car has blown 2 of them, and it is just now 11 years old.
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Old 10-31-2003, 02:00 PM   #11
Mark-44
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Default Re: Heater blows cold air (sothpaw2)

Quote:
Why do the LT1 C4's have such poor heater core design?
I don't know. "It's just another one of those things." Look at it this way, it gives the 'do-it-yourselfers" another thing to become expert at so they can help the rest of us on the forum.

Mark
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Old 10-31-2003, 10:43 PM   #12
SunCr
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Default Re: Heater blows cold air (Mark-44)

I don't think the problem is limited or greater for the LT-1. In my experience and from what I've seen posted here and other boards, some things seem to promote the problem. These include an exhaust leak into the cooling system, Stop Leak products, Coolant Tabs, and Dex-Cool, particularly in a neglected cooling system. The passageways in a typical core are quite small and when they plug up, coolant flows across the top of the core but not through it.
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Old 10-31-2003, 10:43 PM
 
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