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aspiringcarguy's 1965 GTO

2018 April
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rajalx

Heat/ac problem on 1999 grand prix

Question

Hello any one know what causes the heat to only work on the passenger side vents and cold air on the driver side vents,,,its freezing winter and half my heat works,,,but when i let my car sit and idle for awhile the temp gauge gets to about 180 or higher the heat works on the driver side,,but as i drive and the engine temp drops to about 170 to 160 the driver heat stops working and blows cold air while the passenger side blows heat...

is it a sensor or something ? please help....

Roger

1999 grand prix gtp

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16 answers to this question

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Are you getting hot air in the summer instead of A/C through the driver vents too?

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To me it sounds like the actuator for the flapper door maybe starting to go.

The only thing I am not sure of is if the HVAC controls on those years are cable, electric or vacuum.

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To me it sounds like the actuator for the flapper door maybe starting to go.

The only thing I am not sure of is if the HVAC controls on those years are cable, electric or vacuum.

i think its digital dual climate control in that year.

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I can think of a couple of possibilities. Let's start with some questions...

1. Have you flushed and filled your cooling system lately? Say, since September?

2. Have you checked your coolant and overflow bottle levels lately?

3. Have you tested the effectiveness of your water and anti-freeze?

4. Have you done any repair work on the cooling system?

It sound like your car's heater core is either not getting enough coolant or it is paritially plugged somehow. I suspect you have a 180 degree thermostat in your car. Sounds like coolant is not flowing much until you get to the 180 degree mark. You might also be low on coolant.

A plugged radiator or heater core maybe helped with a flush 'n fill. Worst case is that they may need to be replaced. Check all your radiator and heater hoses. They should be hot if the coolant is flowing correctly. If they are old, you might need to replace them

You might have an air bubble in the cooling system. This can cause overheating problems too. This is tough to get rid of if you have one, but you have to be dilligent about checking the coolant. An air bubble could be trapped in your heater core.

Your thermostat could be wrong for the car or may not be working properly. You can test this by removing it from the engine and drop it in a pan of boiling water. Put a thermometer in the water next to it. Drop the thermostat into the water and see what temperature it opens at, or if it opens at all.

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what temps do you have the digital climate control set on?

:lol: also could be a faulty inside air tempture sensor

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Thanks,for all the replies,,my coolant is new,system has been flushed,, the ac works in the summer

my temp setting goes upto 90degrees,but only blows heat out the passenge vents

,cold air driver side,,,,,i will check the other possible causes thanks

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As said, the GTP did have the feature of climate controls, either that the flaps for where the heat flows (vents, windshield, etc) is stuck, or something is physically clogged in the vent system.

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' timestamp='1325818288' post='64159']

As said, the GTP did have the feature of climate controls, either that the flaps for where the heat flows (vents, windshield, etc) is stuck, or something is physically clogged in the vent system.

if it was clogged it woulnt blow cold air out. i think it may be a electric issue

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if it was clogged it woulnt blow cold air out. i think it may be a electric issue

Really? Seems odd that the electronics would allow A/C and not heat...

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' timestamp='1325818639' post='64163']

Really? Seems odd that the electronics would allow A/C and not heat...

Well from what I've read here, If it is dual climate controls, electronics can be sending false signals to the heater core/AC

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Well from what I've read here, If it is dual climate controls, electronics can be sending false signals to the heater core/AC

Maybe it's a fuse? Relay?

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' timestamp='1325819068' post='64172']

Maybe it's a fuse? Relay?

or a senser

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or a senser

Well, it's electronic...is there sort of a resistor unit controlling it? Like how your blower motor resistor blows and you can only use high for example.

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' timestamp='1325819407' post='64176']

Well, it's electronic...is there sort of a resistor unit controlling it? Like how your blower motor resistor blows and you can only use high for example.

im pretty sure their is a senser on both sides of the dash to maintain what temp its set at.

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im pretty sure their is a senser on both sides of the dash to maintain what temp its set at.

Behind the dash to get to it?

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' timestamp='1325820024' post='64187']

Behind the dash to get to it?

i dont know exactly where it is i just know their are sensers. maybe one is faulty

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