GTD AC problem

[Yuji]

Hi, I’ve been driving my GTD40 for more than 20 years in Japan except hot/humid Summer time due to AC. AC has been working well after the maintenance inclusive of compressor replacement while sitting, I mean stopping, but not while driving as hot air from outside comes in. Therefore, I’m not able to drive my toy during Summer time.
Thus, it’ll be appreciated if you could let me know how I could solve this issue?
Thanks
Yuji

 

[DaveC]

Is the hot air coming in through your heater/ac vents or through gaps in the front firewall? My Cobra lets lots of heat into the cockpit from the radiator and headers (radiator in your case). Block off the air gaps.
If it's coming from the vents, where are you bringing fresh air for the hvac in from? Is it in a bad location? Are you getting heat from the radiator? Either move it or block off the fresh air vent and run your a/c on recirc.

If not, your a/c blower is probably also blowing through your heater core. Install a shutoff valve for the coolant to your heater core and keep it blocked off on the summer months.

 

[DaveC]

Mid engine cars also tend to get radiant heat into the cockpit from the engine coolant lines running through the tunnel, make sure that they are insulated. Driving forward can force that hot tunnel air into the cockpit.

So basically you need to find out if it's just hot outside air (mixed with the hot air off your radiator) vs heat from coolant (always-on heater core vs tunnel coolant lines)...

 

[Yuji]

Hi, let me clarify a bit more detail. Since most of the cars has the switch to change either opening the duct? to bring outside air comes in or shut off the duct? for circulating air internally, I’d like to know whether standard GTD has such a switch, but not my toy?
Thanks
Yuji

 

[Mike Pass]

If I read your post correctly you are saying that the AC works OK when the car is stationary but the cabin gets hot air coming in when the car is moving.
If this is the case then either the AC system is getting hot air forced into it or the AC system is being swamped by hot air getting into the cabin. The standard GTD AC system is not very powerful so could easily be overpowered by a lot of hot air entering the car.
Do you have a deep front nostril panel? These help prevent the hot air from the radiator heating the area under the front clip by ducting it more efficiently upwards and away.
Do you have helicopter vents fitted in the side windows? The usual original style little openings are useless. The helicopter vents can scoop in air which helps to slightly pressurise the cabin and also helps to change the hot air air which builds up in the cabin due to the poor ventilation. The angle of the windows makes the cabin like a greenhouse so an efficient exchange of hot air for cooler air is needed.
Check that there are no openings in the front bulkhead which could be letting hot radiator air into the cabin,
A lot of heat gets into the cabin from two other sources. The bulkhead between the cabin and the engine conducts a lot of heat so insulate this area with some of the modern very efficient thin insulation. The hot water tubes pass through the cabin and are very hot and large and release a huge amount of heat into the cabin. I assume they are on the left side as in my GTD. Cover them with as much insulation as you can.
I find that on most hot days the helicopter vents in the windows give a good flow of air and so I use the AC manly when stopped in traffic.
Cheers
Mike

 

[Frank Catt]

Pictures -

 

[Yuji]

Mike,
Thank you so much for letting me know the detail of Std. GTD AC. After the replacing the compressor, I can enjoy pretty cool air thru the ducts when sitting. However hot air comes in thru the ducts once start moving, so never comfortable in Summer.
As I’ve using deep nostril which Frank supplied several years ago, significant reduction of hot air from radiator which is good!
No helicopter vents might help, but I think I need to find how to prevent hot air comes in thru the ducts?

Thanks
Yuji

 

[Denton Mann]

Maybe use a smoke machine flowing backwards from the vents to the ducting to wherever and narrow down the search?

 

[Frank Catt]

Pictures - second attempt. This is what the guys in high temperature areas use !

 

[Yuji]

Frank,

Thank you so much for the suggestion as usual!
Looks no window there!! Let me see.

Best Regards
Yuji

 

[DaveC]

Don't overthink this.
If it's hot air through the VENTS when driving, figure out where the system pulls air from outside of the car. Pull the air from inside the car instead (this is the 'recirc' mode on standard car hvac systems). It's as simple as pulling the fresh air intake hose off of your hvac unit so it's drawing in cabin air instead of outside air that's hot and humid. And blocking off the external air source. This will also significantly drop the humidity in your car.

I wouldn't be surprised if you are running hot coolant through your heater core year-round, this will substantially decrease your evaporator's efficiency. Install a shutoff valve to your heater core for summer use.

You have a functioning a/c system, the last thing I'd do is remove your windows.

1. Run the system on recirc (free)
2. Install shutoff valve to your heater core ($15)
Problem solved. Yes, it's really that simple.

 

[Yuji]

Dave,

Thank you for the follow up. I do need to check where outside air comes in and to install shutoff valve there to prevent hot air.

Regards
Yuji

 

[DaveC]

Dave,

Thank you for the follow up. I do need to check where outside air comes in and to install shutoff valve there to prevent hot air.

Regards
Yuji

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