# Maybe heater problem?
**URL:** https://forums.speedlife.net/t/maybe-heater-problem/103588
**Category:** SON240sx Automotive
**Created:** [February 5, 2007, 9:16pm UTC](https://forums.speedlife.net/t/maybe-heater-problem/103588 "2007-02-05T21:16:45Z")
**Posts on this page:** 12
**Page:** 1
### Author:  [@Dxero](https://forums.speedlife.net/u/Dxero)
#### Post date: [February 5, 2007, 9:16pm UTC](https://forums.speedlife.net/t/maybe-heater-problem/103588/1 "2007-02-05T21:16:45Z")
Ok I don’t know the full mechanics of how a heater works and I’m not so sure if what’s happening to my car is normal for a 240sx. Anyways…the temp gauge on my car can get to operating temp when I leave my car alone in the driveway while it’s on with the heater all the way to the right and the fan turned off, or at #1
Now, when I start driving and then hit the highway, the temp slowly goes down to cold. Even goes down faster if I turn up the fan to lets say 3 or 4. Becomes quite a problem after awhile cuz it’ll be blowing cool air. If I bring down the fan speed or even turn it off, the temp gauge would only then go up once if i’m still in the highway. When I get off the highway, it would then go back close to normal if the fan is at speed 1 or if it’s turned off.
Ok now I don’t believe this is normal, and if it isn’t then my guess is that I’m damaging my engine in some way. So please, help me out, cuz I have no clue why this is happening. Thanks!
Dave
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### Author:  [@system](https://forums.speedlife.net/u/system)
#### Post date: [February 5, 2007, 9:26pm UTC](https://forums.speedlife.net/t/maybe-heater-problem/103588/2 "2007-02-05T21:26:29Z")
well your heater is basicly a fan blowing air over a line filled with heated coolent. being that you are transfering the hear to the moving air it will cause the coolent to cool down more lowering your motor’s temp. It seems like your thermastat is probably stuck in the open position meaning the coolent does not have enough time in the motor to let the temp rise.
just replace your thermostat
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### Author:  [@boostaddict](https://forums.speedlife.net/u/boostaddict)
#### Post date: [February 5, 2007, 10:26pm UTC](https://forums.speedlife.net/t/maybe-heater-problem/103588/3 "2007-02-05T22:26:29Z")
yep, thermostat is probably stuck open. just replace it and you’ll be good to go.
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### Author:  [@Dxero](https://forums.speedlife.net/u/Dxero)
#### Post date: [February 5, 2007, 10:52pm UTC](https://forums.speedlife.net/t/maybe-heater-problem/103588/4 "2007-02-05T22:52:00Z")
i’ve never changed the thermostat nor figured out where exactly it is…is it easy? cuz well…i’m a noob lol
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### Author:  [@boostaddict](https://forums.speedlife.net/u/boostaddict)
#### Post date: [February 6, 2007, 9:35am UTC](https://forums.speedlife.net/t/maybe-heater-problem/103588/5 "2007-02-06T09:35:52Z")
on most cars you undo the upper rad hose from the engine, undo the 2-4 bolts that hold on termostat housing (being the thing you just took the upper rad hose off) and its in there, just get it out, probably need to use a flat head screw driver put in a new one (make sure its in the right way.) with a new gasket (Make sure the old gasket is all gone) bolt it back together and its a job well done.
I was waiting for someone who has done it on a 240 for respond, but since that didn’t happen I thought i’d post.
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### Author:  [@system](https://forums.speedlife.net/u/system)
#### Post date: [February 6, 2007, 10:11pm UTC](https://forums.speedlife.net/t/maybe-heater-problem/103588/6 "2007-02-06T22:11:30Z")
you are correct sir
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### Author:  [@l2iceboy](https://forums.speedlife.net/u/l2iceboy)
#### Post date: [February 6, 2007, 10:13pm UTC](https://forums.speedlife.net/t/maybe-heater-problem/103588/7 "2007-02-06T22:13:36Z")
hey guys, my problem is related, wonderin if it’s the thermostat as well…my heater doesnt work…well the blower works, but it’s not hot/warm air…just cold air lol…the guy i bought it off(got it last week) told me that it _was_ working before he took the deck out…but i’m guessing he didnt drive it for awhile and didnt really check…
but yea, only cold air blows…would it be the thermostat? everything else is fine, meaning the engine runs fine, the temp gauge goes up to normal temp after warming up n stays there while driving…but just blows cold air, it’s all the way to the “red” side and whether it’s on 1-4, all cold air…
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### Author:  [@boostaddict](https://forums.speedlife.net/u/boostaddict)
#### Post date: [February 6, 2007, 10:23pm UTC](https://forums.speedlife.net/t/maybe-heater-problem/103588/8 "2007-02-06T22:23:06Z")
if its staying up at operating temperature youre either getting no coolant into the heater core or its stuck on the cold setting.
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### Author:  [@Dxero](https://forums.speedlife.net/u/Dxero)
#### Post date: [February 7, 2007, 5:43am UTC](https://forums.speedlife.net/t/maybe-heater-problem/103588/9 "2007-02-07T05:43:32Z")
check the fuse on your panel just by the drivers door. might have crossed some wires cuz i think one of them is related to heater and ac.
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### Author:  [@S13GG](https://forums.speedlife.net/u/S13GG)
#### Post date: [February 7, 2007, 6:34am UTC](https://forums.speedlife.net/t/maybe-heater-problem/103588/10 "2007-02-07T06:34:49Z")
> [@l2iceboy"](#):
>
> hey guys, my problem is related, wonderin if it’s the thermostat as well…my heater doesnt work…well the blower works, but it’s not hot/warm air…just cold air lol…the guy i bought it off(got it last week) told me that it _was_ working before he took the deck out…but i’m guessing he didnt drive it for awhile and didnt really check…
>
> but yea, only cold air blows…would it be the thermostat? everything else is fine, meaning the engine runs fine, the temp gauge goes up to normal temp after warming up n stays there while driving…but just blows cold air, it’s all the way to the “red” side and whether it’s on 1-4, all cold air…
I had a CD player stolen from one of my S13’s, the hack who removed it managed to disconnect the metal (plastic sleeve)wire that connects your temp selector to your airbox. Took me about an hour to correct/re-connect the wire.
Its a metal wire (not for electricity) within a whiteish plastic covering.
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### Author:  [@chineybutu](https://forums.speedlife.net/u/chineybutu)
#### Post date: [February 7, 2007, 2:20pm UTC](https://forums.speedlife.net/t/maybe-heater-problem/103588/11 "2007-02-07T14:20:09Z")
yeee same problem i had, temp gauge would goto cold while driving, just replace thermostat and your good to go,
WOuld a stuck open Thermostat give you bad gas mileage?
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### Author:  [@Mista\_Sparkoh](https://forums.speedlife.net/u/Mista_Sparkoh)
#### Post date: [February 11, 2007, 8:36am UTC](https://forums.speedlife.net/t/maybe-heater-problem/103588/12 "2007-02-11T08:36:48Z")
> [@HC Turbo Manifold](https://forums.speedlife.net/t/hc-turbo-manifold/8532/25):
>
> yeee same problem i had, temp gauge would goto cold while driving, just replace thermostat and your good to go,
>
> WOuld a stuck open Thermostat give you bad gas mileage?
apparently it does
I had the same problem but for some reason, when I got a used SR thermo from matty, it’s smaller than the one I have
I jus replaced it but it seems that my original therm didn’t look like it was stuck open because the bottoms spring can still move.