Modern AC in a 308

I have owned my 308QV for over 30 years. The air conditioning system has always ranged between useless and worthless. I live in the sunbelt area of the US where temperatures can reach 90F or more degrees every month of the year. It can get really hot in the summer! I decided it’s time to upgrade the 308 AC system to modern car standards.

First rule for mods- My philosophy for this and all upgrades. No drilling/cutting or modifying the car body/frame or wiring. All mods can be fully reversed. The only item that deviated from this was the evaporator box, it was falling apart, so I didn’t mind cutting or re-working it. A replacement evaporator plenum would allow for return to stock should someone desire to be hot in the summer.

There are lots of good threads on FC detailing AC fixes and improvements. I think the consensus is the AC will blow cold air if everything is in working order but lacks sufficient blower speed/circulation/vents to cool the car, driver, or passenger on a 90F+ degree day. That is certainly the case for my car. There just isn’t enough directable airflow.

My AC needed a few repairs prior to upgrading the low airflow issue. If your AC works properly and you are interested in just upgrading the air flow issues. Skip to the end.

Preparation

I replaced the hi & lo pressure lines with new Vintage air lines w/new connectors. This eliminated Freon leaks from the old hoses. The Vintage air hoses have a smaller exterior diameter than the originals and are easier to pull thru the chassis. Not easy, but easier! In fact, there was enough room to also pull one of the turbo intercooler lines (5/8”) thru the same chase-way as the AC lines.

Additionally, I insulated the console tunnel to minimize heat from the water pipes traversing the car.

Replaced the R-12 expansion valve with an identical unit from NAPA designed for R134a ($35 USD)

When using R-134a, the AC would not blow cold air when the car was idling but worked ok when driving (just not much air). Lack of airflow across the condenser was the culprit. I replaced the condenser with a new larger aluminum cross flow unit, along with a new aluminum radiator. I constructed and fully shrouded the new condenser and radiators including installing 2- 10” Spal fans. Weight savings was about 8lbs.

See pic.

Once I had a solid AC system it was time to address the other shortcomings.

Blower motor

Replaced the cabin blower motor with upgraded blower from Spal.

Installed new aluminum plate in the evaporator for blower motor mounting as required.

The evaporator box was literally falling apart when I removed it. A bunch of fiberglass repairs along with the new aluminum plate made it better/stronger than new.

See pic

Blower motor voltage fix

There is a large voltage drop to the blower motor due to the wire-wound voltage divider that limits the fans speed/power. I used a relay to supply 13.8VDC directly to the blower motor when hi speed is selected. This made a 30% increase in air speed out of the ducts when max is selected compared to the stock arrangement. I did not increase the voltage/blower speed for mid and low power settings although that is changeable if desired.
Most of these fixes have been covered elsewhere on FC. I think most of the updates below are new.

The VENT FIX

Most cars/trucks/SUV’s have a least 4 large forward facing AC vents on the dash. I think this is a minimum requirement for decent AC operation. To remedy this, I decided to remove the existing car radio that I never use and install 2 new AC vents in its place. Weight saving 5lbs. This freed up valuable space next to the evaporator and allows for the construction of a proper air vents and ducting. I constructed the new ducts from fiberglass and wood. I constructed the vent surrounds from wood and wrapped them in marine grade vinyl.

See photos

Most HVAC controls systems can switch between forward vents or defrost vents. I decided the 308 would benefit from this feature as well. I built a flapper valve in the defrost exit of the evap. box to stop or vary the amount of air going to defrost vents. The choke cable temporarily mounted under the lower vents to control the flapper valve. Depending on how testing proceeds I may convert the manual cable and devise an electric control for the flapper valve.

See photos

Next- I upsized the 2 existing small under dash vents and moved them slightly forward. To feed the new larger vents I redesigned the plenum with a larger opening and built a duct for the two new lower vents. This improvement provided more foot room near the gas pedal as well as allowing more airflow. This is welcome improvement in foot room around the gas pedal.

Results- I baselined the airspeed from 4 different vehicles to see how the 308 compares. I used a handheld anemometer to measure the highest air speed from each vent for comparison. I can post a table of the results for those interested. The 308 exceeded all the other vehicles airflow by a wide margin!

Results- The 308 now exceeds every vehicle I tested across all 4 vents. Vehicle comparisons Toyota 4-Runner, Chevy Silverado, Kia Soul

All 4 vents are fully adjustable up/down right/left. The airflow is strong enough to support a couple of floor vents if desired.

Ferrari provided us with suitable basic components to deliver cold AC. It just needs work on the delivery system. This was my solution. I hope others can benefit.
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About 25-30% by my measurements

 

My car came with a block-off plate and no radio. So I don't know if Ferrari intended for a radio to go in that spot or a homemade vent
I contemplated installing a Bluetooth radio and using a smartphone for music. Then I realized I hadn't listened to the radio in more than a year. So, I probably will just listen to the music of the turbo and shifting gears. But I will be cool doing it!

 

Ray,
I located the relay in the passenger side footwell. Depending on your year model there may be several devices located their. Euro cars may only have the interior dome light timer. Lots of room to mount the relay. Sorry, I dont have photos. I will attached a schematic with my notes. Hope that helps. You do not need to cut any wiires! Just unplug the proper red wire on the fan speed switch to triger the relay. Run a wire from the fan switch to the relay. Parrellel existing connection at blower motor.
However, while this will increase your blower speed, it is still like trying to blow air thru a straw!

 

Mike,Yes, the mod only affects the high speed setting.

 

I want to add a few observations from bench testing as the project progressed.

For most people who are unhappy with their 3x8 AC system. Just upgrading the upper or lower vents will make a huge improvement. I did not want to come up short, so I added the upper vent and increased the lower vent size.

It may not have been clear in my photos, but the upper duct and the lower ducts are completely separate.

The stock 3x8 evaporator has approx. 4in vent for the defroster and less than 3in for the lower vents. The defrost vent system is very inefficient. That’s why I added the control flapper valve to shut off o reduce the defrost flow when desired.

There may be some marginal gains by re-working the evaporator housing while maintaining the stock appearance (restrict the flow to the defroster etc.).

The AC is quieter with the new blower. Less restrictive evap plenum helps. Think of a vacuum cleaner when you hold your hand of the end and release it.

Choose the upgrades you can live with.

 

30C is often our low temp at night

 

Sure. It will need to be on a weekend for the next few months. PM me and I will send you my phone #
Ron