Warm air through vents

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Saltman
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Warm air through vents

Post by Saltman » 26 Apr 2009 07:30

Hi Eveyone

My 2007 4.8GL has an annoying feature! I have not yet found the pattern to it, but here are the symptoms:

I have found on occassion that the interior becomes quite warm, even when the top vents are set to cold air only. At first I thought it was the sunlight through the untinted windows, but now on a number of occassions I have realised (confirmed by friends that travelled with me) that it is actually hot air that enters the cabin through the vents.

Has anyone else come across this problem and if so, how was it solved?
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Re: Warm air through vents

Post by Vaatjie » 27 Apr 2009 08:36

Yes herbie, got the same problem. Will ask Nissan to check it out.
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Re: Warm air through vents

Post by fralanti » 07 May 2009 14:19

I also have the same problem, and mine is a little older model. Let me know if you find a cure.
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Re: Warm air through vents

Post by Saltman » 07 May 2009 18:29

Having had a look at the Aussie Patrol Forum (Patrol4x4.com), they recognize this as part of the Patrol terrirtory and I have not yet picked up a real solution.
Here are some of their comments which might help us to start looking at possible causes:

1. The air pickup is from the vents which are in front of the windscreen on the outside.
2. Maybe there is a lot of heat transfer through the panels and hot air gets dragged in as a result, but it still does not explain why when on recirc with windows down nothing changes.
3. Always thought it was that the heater flap doesn't close allowing hot air into the cabin. I was going to fit a valve to the heater hose to hopefully stop the problem.

I intend taking the issue to Nissan on Friday, but in the meantime I am going with the warm air flow theory through the vent intakes. Now I want to look at possible solutions - will wait to see what Nissan has to say.

Where is that Nissan Patrol 4.8 Manual!!! Any news on the softcopy version ... ? :pray:
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Re: Warm air through vents

Post by Ross » 27 May 2009 14:48

Yep...I have this problem as well. With my van it is noticably worse at low speed (eg when driving off road), and I have always thought that it was just the heat soak from the turbo. It would be nice to solve it, as it does get quite annoying. Earlier in the year on a 40degree day driving through Baviaanskllof, the effect was such that the aircon could not completely overcome it, and actually cut out completely (must have some sort of safety that cuts in when the compressor works too hard).

If anyone finds a solution please keep us posted!
Ross

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Re: Warm air through vents

Post by Saltman » 27 May 2009 19:25

Hi Ross and welcome!

I have spoken to Imperial Nissan (Parow) and there are 2 possibilities as the root cause:
1. The vents are controlled by flaps. The hot air stems from the warm water that is circulated through the pipework continuously.
The only barrier that prevents the heat from being circulated through the cabin is a set of flaps (or air mix doors as Nissan calls them) that are operated by the radial knobs (in the case of the 4.8 GL with manual controls) It is suspected that a flap (or more than one) does not close properly when the setting is selected on the dash.

2. The second option is that the warm air does indeed come from the external vents and this would explain why the air remains warm when the vehicle works hard in offroad conditions at low speed.

How to check? - verify where the warm air comes from.
Check that the flaps close properly, a mission as you have to take the dash partly to pieces to get to them!
Put a deflector between the bonnet and the vent intakes in an attempt to block the heat flow from reaching the intakes.
Put a thermometer in the internal cabin vent exits and measure the temperatures and compare with ambient external temperature.

Short term fix? Run with the aircon on ...

And that brings me to Ross's second problem. The a/c stopped working. I do not have that much experience with the Patrol a/c system, but if it is a fairly standard system then one potential problem I have experienced on other vehicles in extreme heat conditions where the a/c has to work very hard, is that the system "freezes up". To overcome this problem I have learnt not to run the a/c flat out, but to maintain an "in between" setting. Instead of running the compressor flatout, it then cycles and prevents the freezing up from occurring.

My 2 cents plus VAT's worth ... Please post a response and let us know if a suggestion does indeed work.
Thanks
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Re: Warm air through vents

Post by tour de frans » 28 May 2009 22:32

Patrols are clever
When you are useing the ac, the electric fan in the front comes on to help with the air flow through the condensor and radiator.There is a sensor in the radiator(a normaly open switch)that will switch the ac pump off,(yet the electric fan stays on) to prevent the enjine from over heating.Reason, the condensor gets hot infront off the radiator when the ac is on.The switch will only cut the ac pump in very hot conditions or with a blocked radiator,over heating problems.The 4.5s has one switch on driver side off radiator and the 4.2s has got two switches both sides off the radiator.The petrol Patrols has two fans in the front and the diesels only one. (that is the GUs,i am not sure about the other models.)
So, if your heat guage is normal and the ac is working and it is hot outside,and you are working your Patrol and the ac suddenly stop working watch the heat guage.It should not climb,but you know the car cutting the ac is only making life easy for the water in the radiator too cool better.
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Re: Warm air through vents

Post by Saltman » 21 Feb 2010 08:07

OK, the problem is still there after Nissan has checked that the flaps close properly.
Due to the permanent flow of hot (engine temperature) water through the heater matrix, the heat will always be in the cabin, but masked by the flaps.
On a hot day or slow offroad driving where a lot of engine heat is generated that is not quickly dissipated by airflow (wind), the flaps also heat up and subsequently the heat is transferred to the airflow that passes the flaps on its way to the interior airvents.

I am proposing the following solution, but would like some crirital comment on whether it is a good solution, or whether I am missing some vital point:

I would like to insert a manual valve in the hot water line before the firewall in the engine bay. That way I can close the valve in summer and open it in winter if I need hot air in the vehicle.

Can anyone think of detrimental impacts I need to watch out for?
Under what type of pressure does the system operate and what type of valve would be best suited to the job?

The older VW's (Golfs etc) had such a valve in the line and there one had to follow a maintenance routine to prevent the heater radiator from rusting through if not used and the valve getting stuck - the preventive measure was to open the valve once a week or so to allow hot water to flow through it and therefore ensure "clean" water in the heater.

I am going to Botswana for a month and do not wish to drive with the aircon on all the time due to hot air through the vents (serious impact on the fuel consumption when driving slowly) I am therefore hoping this mod will solve the problem.

Cheers
Herbie
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Re: Warm air through vents

Post by Family_Dog » 22 Feb 2010 07:33

I don't see any problem with this, many of the older cars had just such a system. Just ensure you use high-quality components and good hose clamps, you certainly do not want any leaks to develop there.


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Re: Warm air through vents

Post by AndriesS » 22 Feb 2010 07:58

I'm not that familiar with the Patrol yet and the solution should work- if you want to get snazy get add a cable and link it to a new slider mechanism in the dashboard. I would shop around for cars that used a cable operated valve that did not ever give problems (notably not Opel heater valves).

Just check that nothing is dependent on the water downstream, i.e. something that might need water for enriching, or cooling of something else. if thats the case you might need either two way valve or two valves and add a junction on the return pipe.


I have noticed by AC does from time to time cycle often (i.e. revs at idle drop from 900(AC pump on) to 700 (AC pump off)) and will check whether it need regassing. I've also noticed that AC pipes on mine does not have any thermal insulation, maybe some thermal insulation in the engine bay will increase efficiency.

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