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No hot air from car heater


TheRealNips
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So for the past week the car hasn't been giving out any heat, Its been off the road since beginning of October due to failing its MOT. I finally got a pass and started driving it again to find it wont blow hot air. This may have been a longer problem as I wouldn't have noticed it during the summer, it was definatly warm last winter.

Using the service manual (http://www.300zx-twinturbo.com/cgi-bin/manual.cgi?list=ha&slide=125) I found the sensors 52 & 55 have open circuits leading me to diagnostic 6 & 12. I decided to start at 6 and got stuck, (http://www.300zx-twinturbo.com/cgi-bin/manual.cgi?list=ha&slide=142)

I cant seem to find where the sensor actually is. I was on my back on a fully reclined drivers seat with my head by the pedals (much to the amusement of my neighbours) looking at the ducting and found possibly a duct with a sensor with a two wire plug that I cant seem to separate. There is also a plug leading into the same loom as the aforementioned plug that has three wires but no where to plug into. These two plugs seem to match to the diagrams here: http://www.300zx-twinturbo.com/cgi-bin/manual.cgi?list=ha&slide=165 (The in-vehicle sensor lower & foot duct sensor) but the diagram of the shape of the ducts don't seem to match or the location of the sensors on the actual ducts.

There also seems to be a short piece or ducting missing from the centre area of the dash leading to the duct that I mentioned. The is also a rubber hose (maybe 1" diameter) not plugged into anything. The duct should attach to the side of what looks like the motors/mechanisms that move the flaps that change air flow and air temperature. I have attached a link to a short video I took to show the area of the missing duct, the three wire plug missing something to plug into and the two wire plug. 

 

I have done the usual check coolant level etc and have done the actuator test and all the motors seem to move the flaps when told to following this: (http://www.300zx-twinturbo.com/cgi-bin/manual.cgi?list=ha&slide=119) so I don't think its jammed in the cold position. All the other sensors are working fine and the only two fault codes are 2 & 5 which are lower and floor open circuits. I think they have become unplugged or not even plugged back in after a garage has done some work. 

Could someone explain to me where those two sensors are located so I can try and plug them and test them?

Thanks

 

 

1990 Black MT NA LWB = 2014 - 2020 (Sold)

1991 Red MT TT LWB = 2015 - 2017 (Stripped & Scrapped)

1991 Red MT TT LWB = 2017 - 2021 (Sold)

1991 Black MT TT LWB = 2018 - 2021 (Sold)

1989 Red AT TT LWB = 2021 - XXXX (Kept)

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I have just fixed the same problem yesterday. Which ended up being a stuck closed thermostat. I would check your bottom radiator hose if it is cold or barely warm when engine is hot. Could be something as simple as that. Tho not the easiest to replace.

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4 hours ago, Tutis said:

I have just fixed the same problem yesterday. Which ended up being a stuck closed thermostat. I would check your bottom radiator hose if it is cold or barely warm when engine is hot. Could be something as simple as that. Tho not the easiest to replace.

Cool, thanks. I'll drive it tomorrow and see. Would that make the car engine warm up quicker than usual. I've noticed I get to normal running temperature quicker than usual when going to work.

1990 Black MT NA LWB = 2014 - 2020 (Sold)

1991 Red MT TT LWB = 2015 - 2017 (Stripped & Scrapped)

1991 Red MT TT LWB = 2017 - 2021 (Sold)

1991 Black MT TT LWB = 2018 - 2021 (Sold)

1989 Red AT TT LWB = 2021 - XXXX (Kept)

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39 minutes ago, Tutis said:

Temp gauge would go up in about 5mins. If you drive keep an eye on the temp as it could overheat quickly

It doesnt overheat, just gets to temp very quickly and stay normal for my 11 mile commute

1990 Black MT NA LWB = 2014 - 2020 (Sold)

1991 Red MT TT LWB = 2015 - 2017 (Stripped & Scrapped)

1991 Red MT TT LWB = 2017 - 2021 (Sold)

1991 Black MT TT LWB = 2018 - 2021 (Sold)

1989 Red AT TT LWB = 2021 - XXXX (Kept)

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Mine wasnt either. I guess only because it is cold up here in scotland. The thermostat was definatelly stuck, didnt pass the tea test ?. Radiator was also cold at the bottom. And thats after 15mile commute. The replacement thermostat opened straight away when i put boiling water over it. Both same opening at 76.5c. It actually is not that hard to do. I managed with the radiator shroud on. If you find thats the problem let me know. I will go step by step how i did it.

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On 07/12/2020 at 16:58, Tutis said:

I have just fixed the same problem yesterday. Which ended up being a stuck closed thermostat. I would check your bottom radiator hose if it is cold or barely warm when engine is hot. Could be something as simple as that. Tho not the easiest to replace.

I had a similar - albeit intermittent - issue with my heater last autumn. On those occasionally cold mornings, I found the heater only blew out cold air, yet later in the day, it worked fine.

Then after Jimmer did a 120k service, cambelt, tensioners and a more significant to this thread, a new thermostat, the heater works fine once more.......?

I have something to say............ It's better to burn out than to fade away..... :tt2:

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