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1995 300tdi ROW
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Discussion Starter · #1 · (Edited)
So I figured I'd pass along how I did my AC kit as I did deviate from the original design a bit.

Starting with the wiring, I added another relay and have it setup so that when the AC is on it will automatically start the fan. When the AC is off, the normally closed contact off relay 1 will power relay 2 so that if the pressure is high in the system it will power the fan.


For the wiring itself, I did add a dedicated fuse block from painless and a bypass valve so that when the valve is closed it will loop coolant back to the engine.(as pictured) I did have to modify the throw of the valve so it would fully open n close


For the compressor itself, I did have to grind the top mounts as they were hitting the hood


For the switch itself, I originally installed the rotary knob But didn't like that it didn't match. i also opted use an own OEM style switch for the engagement of the AC itself. (Not pictured is the OEM style switch mounted under the cluster on the left side in that blank) I wired it up to an unused indicator in the warning cluster. I also modified the stock 2 position switched ground switch to use a 3 position switched positive for the fan speed control.






Also installed dash vents into the mudstuff center console.

 

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1989 D90 ("The Coal Must Roll") | 1997 D110 ("Sweet Coniston Green Bliss")
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I realize that it is now the wrong season for a real test, but how much cold air does your "Ministry of Defender" system put out? (And how does it compare to the "standard" under dash systems?)
 

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1995 300tdi ROW
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Discussion Starter · #7 · (Edited)
What vents are those and also the stereo head?
The vents are from nostalgic ac. The quantity from the screenshot needs to be changed based on your needs. For the ducting, for 2 vents and adaptors I went with 2 feet, but looking back go with 3. Will make taking off the console easier.

For the radio I went with this unit because it was cheap to be honest. I mounted the unit to the back of the console using 2 of the screws used for mounting the console and I mounted the screen itself to the face of the console. The ribbon cable is pleny long enough to reach. The attached picture was before I added AC so it doesn't show the ducts. But they are mounted along the sides of the radio into the HVAC plenum


 

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I realize that it is now the wrong season for a real test, but how much cold air does your "Ministry of Defender" system put out? (And how does it compare to the "standard" under dash systems?)
I had Trevor (https://www.british4x4specialists.com/) put mine in last year, It made a HUGE difference in the height of summer. I'm very impressed with it. The issue now is the total lack of insulation (and cracks) keeping the cold air in.
 

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The issue now is the total lack of insulation (and cracks) keeping the cold air in.
I think this is the point most people miss with both heating and cooling. The stock trucks have zero insulation. Adding insulation and stopping drafts should be the number one job.
 
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I think this is the point most people miss with both heating and cooling. The stock trucks have zero insulation. Adding insulation and stopping drafts should be the number one job.
This AND, in talking to Jonathan at MOD, figuring out a way to remove hot air. From his POV, the unit has ample capability in being able to supply cold air into the cabin but the main issue is being able to exhaust the hot air.
 

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This AND, in talking to Jonathan at MOD, figuring out a way to remove hot air. From his POV, the unit has ample capability in being able to supply cold air into the cabin but the main issue is being able to exhaust the hot air.
That statement does not make sense, since he designed it as a full recirculation system. It does not do anything to change air. In a cooling mode, there is no need to exhaust air. Recirculation improves cooling performance.

When in heating mode, you must bring in fresh air or the humidity will simply increase until there is mass condensation. The way the system is designed would make it unusable for heating in a cold climate.
 
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That statement does not make sense, since he designed it as a full recirculation system. It does not do anything to change air. In a cooling mode, there is no need to exhaust air. Recirculation improves cooling performance.
From him directly:
The Defender is basically a tin shed on wheels. It has no thermal
efficiency and was never meant to have AC at all...

Modern cars are designed with AC in mind and have underfloor and side
pillar ventilation outlets as well as pressure vents to circulate the
air and maintain a regulated temperature.

Therefore, everything we do to the Defender is in some way compromised
by the basic design, which is now 50+ yrs old.

The #1 problem is not about adding AC and getting cold air in... It's
about getting the hot air out. This is the biggest issue by far.

The best advice I can give is to add roof vents towards the rear of the
truck to allow hot air out. This for sure is the most effective solution
to cooling on a Defender, without doubt.

On mine, I added a Subaru Impreza hood scoop to the roof, but in
reverse. So rather than doing its usual job of forcing air into an
engine bay, it creates a low pressure above and actually sucks hot air
out.

This makes a massive difference because as it draws hot air out, it
pulls cold air from the front.

Adding insulation makes very little difference.
 

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The guy is clueless and makes no sense. He designed a recirculation system with NO air exchange and then suggests air exchange is important. It is not for cooling. Less air exchange is better. I can explain the reasons, if you want. Stating that adding insulation makes little difference makes me feel like I'm talking to an anti-vaxxer.
 
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Why are the pressure and temp switches on a relay? You can get receiver-dryers with both sensors built in so you just daisy chain them into the circuit for the compressor clutch.
 
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Discussion Starter · #19 ·
Didn't wanna run that many amps thru the high/low pressure sensor on the receiver drier so I use it to trigger the relay to run the fan that draws almost 15 or 20 amps. If it was just for the clutch I wouldn't use the relays.

As for the temp, I think the limiting factor is the amount of air in the summer. And right now in the winter my truck barely reaches 150°F so the air coming out isn't that hot. I am going to try blocking a bit of the radiator to try n get the engine temps up. I have the AC grill that has that extra opening at the bottom
 

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If your engine is not getting to temperature, your thermostat is most likely leaking. It can be a crap shoot to find ones that seal. I've run down to -40 and have no heat issues.
 
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