Box Fans on Deck Lid A/C Condensor Work

Hugh R · 08:01 AM

Installed 3-4" 12 volt computer-type box fans on the rear deck lid condensor and I saw bumper-to-bumper center dash temperatures drop from 60 F to 48 F. It was about 95 degrees F outside. With no other modifications. I would have installed more box fans, but that's all I had room for between the cooling fan and the A/C compressor. I connected the fans to the wires that power the back left fender A/C condensor fan on my 84 ROW Targa. Total cost for the fans, wire, wire ties, and a small electrical connection block was $18.75. I saw no change in engine oil temperature. Its not exactly cold inside, but its certainly tolerable.

88911coupe · 09-03-2003, 08:14 AM

Could you give some detail about "to the wires that power the back left fender A/C condensor fan"? I am not sure what this is referring to.
Thanks,

Hugh R · 09-03-2003, 08:41 AM

My 84 has an A/C condensor in the back left quarter panel. It has a cooling fan that comes on when the A/C is turned on (you can see and hear the fan). I snipped the wire ties that hold the fan wires and reached up on the car front side of the fan and unplugged the two connector plug that powers the fan. Then, I carefully peeled back the insulation on the wires and soldered in the new wires to power the new fans. I then electrical taped and shrink wrapped the connects and plugged the existing fan connector back in. When the A/C is on, the original quarter panel condensor fan and the three new deck lid condensor fans come on.

targa80 · targa80's Garage

How about some pictures of the fan setup and location?

Hugh R · 09-03-2003, 08:49 AM

I'll try and take some pics tonight when I get home.

Jim Sims · 09-03-2003, 08:52 AM

I would check your model year wiring diagram to see if the left rear quarter panel condenser fan is powered through the A/C switch contacts up front or through a relay. If through the switch you are likely putting a lot of current through that switch (front condenser fan?, rear condenser fan, the three fans you added to the decklid plus the compressor clutch). I know of a case where the A/C switch failed (contacts burned up - fans and compressor clutch were fine) with just the OEM set-up currents flowing through it. If there is no relay in the system you may want to consider adding one. Cheers, Jim

krichard · krichard's Garage

Are the fans sucking air into the deck lid or blowing out? Also how did you mount them?

Hugh R · 09-03-2003, 10:21 AM

Jim

Your right, I should check on the system to see if it has a relay. The fans draw 0.36 amps each or about 1.2 amps total. I used plastic wire ties to attach the fans through the condensor fins. You have to remove five screws from the condensor holding bracket and drop the condensor down an inch or two, then reattach. No need to break any freon lines. The fans suck into the engine compartment

scottb · 09-03-2003, 11:42 AM

What's the CFM rating on each fan?

Hugh R · 09-03-2003, 02:33 PM

I think they're about 250 CFM each. Computer surplus stores usually sell slow, medium and fast speed. The slow speed (100 CFM are about 0.16 Amps and the fast 250 CFM are about 0.32 Amps. Faster are noisier, but inside an engine compartment, who cares. Outside you can barely hear them.

silverc4s · silverc4s's Garage

The condensor / fan unit in your left rear qtr panel sounds like the ProCooler unit, a fairly well-known add-on for P cars..

Hugh R · 09-03-2003, 06:30 PM

Here are pics of the box fans on the deck lid condensor and the fan on the condensor in the left rear quarter panel. Since I've only owned the car a few months, I don't know if its original or not. I don't seem to have a front condensor. In the picture of the quarter panel fan/condensor you can see a white plug to the right of the fan in the background, that is what I pulled (after snipping a couple of wire ties) and I soldered in the wires for the new deck lid condensor fans.

In response to previous post, I don't know if its wired to a relay or not. I know its not wired to any of the relays in the front fuse box, or the relay in the smuggler box. I'll have to keep looking, but it seems OK, and the fan and t-stat controls on the dash seem OK. I'd stick in another fan or two, but those were the only places that I could squeeze them in with them striking the engine fan or the A/C compressor. The temp used to go up to 70 or more at the center A/C vent at idle and bumper-to-bumper traffic here in LA. Now it stay pretty consistent at 48-51 degrees. Also, I can run the top outside air vent and fan to get a good breeze and it cools that down as well and keeps it at 48-51.

Lucky · 09-03-2003, 06:39 PM

Hugh,

Great idea... one question: how much moisture/dirt/heat can those computer fans take?

Hugh R · 07:31 PM

I don't know, I'm Beta testing this. When was the last time you heard of a computer box fan crapping out. Besides, at $3.25 each and about two minutes to put new ones in, they can crap out every year for all I care. BTW, they make slow, medium and fast, speeds and 1" and I think 2" thick, get the faster and thinner ones if you need the space.

turbo6bar · 09-04-2003, 04:29 AM

Hugh, one of the reasons this might work so well for you is the fact air can totally bypass the A/C condenser when pulled in by the engine fan. Air will take the path of least resistance, which is through the unobstructed deck lid grill. 930s use this style condenser to accomodate an intercooler, if I'm not mistaken?

The stock condenser on non-turbo models covers the entire decklid grill surface, so most of the air pulled in by the engine fan is pulled through the condenser.

Griffiths sells the rear quarter panel condenser unit, as well.

Jürgen

911pcars · 09-04-2003, 02:20 PM

Do your fans work all the time or just at low speed? I'd think you wouldn't need them once you got up to a certain vehicle speed.

If you A-B compared the outlet temps at a steady speed with and without the fans working, you'd know whether they're necessary at that point.

If effective only at low speed, then you could connect the source wires to a mercury switch to sense throttle opening or some other vehicle/engine speed-related signal.

It'd also be trick to reverse the polarity so the fans blow air OUT of the engine compartment once the engine is OFF using a timer relay in order to reduce engine heat soak and to transfer more heat out of the condenser.

Some ideas to consider,
Sherwood Lee
http://members.rennlist.org/911pcars

Hugh R · 09-04-2003, 03:30 PM

Since the fans are connected to the rear quarter panel condensor fan, they will cycle with the t-Stat. Turbo6bar, your right, the engine fan doesn't pull air through the rear deck A/C condensor, which is exactly why I put them in. Since I live in LA, stop and go is a way of life, and since it takes time for the freon to cool down once I get going, having the fans run off the other condensor fan makes sense.