J-Rat

iTrader: (2)

So, I have been dabbling in AC with limited success for some time now, so when my wife decided to buy an 89 Vert with no AC, I knew I had that fix locked down, but in reality I learned a pretty valuable lesson about AC and electric fan cooled cars.

The basic lesson here is, if you have a car thats cooled by an electric fan, be SURE you have a default that trips the fan to FULL ON when your AC is utilized, or the pressure in the condenser will rise to really cool levels and blow up the receiver dryer, as my wife found out the next day.

I wouldn't have even known this neat little fact if I had not hooked up a manifold gauge set to the system (after I repaired the damage), and was trying to recharge it. The pressure kept going high, then all of a sudden the coolant got hot enough to trip the E-Fan. Unbelievably enough, thats when the pressure dropped 100 PSI on the high side. Thats when I figured out why Black Magic 150 fans have a default port for AC that turns in full on when the AC is used...

So if you blew up your AC, and you are on electric fans only, this is probably why. And this is ALSO WHY I am going back to a STOCK FAN!

micah

So are you saying that e-fans aren't enough for AC+Rad in the summer? Or only if the e-fan isn't configured to come on FULL with AC?

scrip7

iTrader: (6)

Here's another lesson for us with 7s. Our stock condenser is a "serpentine" design, meaning it has a flat tube that runs back and forth across it from top to bottom. With r12, it is efficient enough with a stock fan or electric if it's on any time the compressor is on. If we convert to r134a, the efficiency of the stock condenser isn't enough to keep high side pressures at a level for good cooling. One thing that helps, as I did on my n/a, is to use a TII stock electric "pusher" fan in front of the condenser, and wire it with a relay so that it's on any time the compressor is on. The best way to get r134a to cool like newer cars is to go with a universal "parallel flow" condenser which has many more tubes (smaller, narrower ones) and more capacity and efficiency than a serpentine condenser. Hoses would have to be custom made to use this type of condenser, but it's not expensive to have it done. I plan on doing this type of condenser swap, but it's another project of it's own. I will do a writeup with pics some day.

scrip7

iTrader: (6)

Just for opinion's sake, I haven't seen an electric fan cover the entire surface area of our radiators and most have a minimal shroud at best. The s5 fan is a 10-blade mother humper and with a shroud and a functioning clutch it pulls tons of air across all of the radiator. You won't see me go with an electric EVER. PERIOD.

J-Rat

iTrader: (2)

Agreed.. We got the car with the E-Fan already installed.. I just have to source the parts to reconvert it.

J-Rat

iTrader: (2)

The E-fan is fine, but it needs to come on as SOON as the compressor is kicked on. It cant wait for the coolant to trip the fan.

And whats with this SERVER TOO BUSY crap?

ramello

iTrader: (1)

not to hijack but yea its becoming a pain in the *** like every other page i try to view keeps coming up too busy!

slo

iTrader: (1)

My 90 GTU which was originally an Auto trans car, came with the E fan in front of the condenser, as it was stock the efan came on only with the AC.

J-Rat

iTrader: (2)

Yep, some do come with that fan.. its in ADDITION to the stock fan.

Sideways7

iTrader: (7)

I actually have the stock e-fan, which I am going to put back in whenever I get around to fixing my A/C system. I am actually screwing with the a/c system in my DD (a MX-3) which is remarkably similar to the FC. It has 2 e-fans covering the radiator (and condenser obviously). I had been wondering why it stopped cooling when I stopped driving, and I though that the system was just overcharged or something. I just noticed yesterday that only one of the fans was turning, so I might have found my problems. That or 1 is only for when the coolant gets hot enough, I haven't figured out yet. I just know that the car has never overheated.
Also, I never realized how blessed we all are with the vast support we have for these cars. Whenever I try to find anything about the MX-3 there's just nothing out there like this. Just 1 forum thats so-so at best.

scrip7

iTrader: (6)

I concur. Despite some of the flaming and bashing and misinformation, there is a wealth of good input from people that have gone through lots of crap with their 7s and a few good stories as well. Kudos to the people that keep this boat afloat. I have subscribed to a couple other rx7 forums, but they're pretty much ghost towns when I visit them. I mostly come here daily to offer what I can.

arghx

iTrader: (3)

yeah if i recall correctly the FD will automatically switch on one of its electric fans if the A/C comes on

oh and +1 for the stock clutch fan. I have kept my stock fan on my T2 even though I am just about done with a full turbo upgrade. so I have the stock clutch fan with a T04S and HKS log manifold. the clearance is tight but it works (had to cut a small portion of the fan shroud to fit in the intake).

RotaMan99

So you should wire a relay to the AC clutch wire to activate the fan right? I havn't messed with A/C so I wouldn't know.

HAILERS

For what it's worth...............On the stock ECU, there is an output from 1F that puts a gnd on a relay whenever the a/c is turned on.

pfsantos

iTrader: (1)

Yes. If you look at the '88 FSM wiring diagram portion showing the auxiliary electric fan, the only model exclusion is 5sp. Non-turbo. So all Automatics and Turbo's should have them from factory.

jackhild59

iTrader: (7)

Not too harsh of a lesson-since no one got hurt.

Here is an item that is a must for anyone who is converting to 134A:

http://www.ackits.com/merchant.mvc?S...onversionitems

The switch fits over your high side access port -3/16" on our RX7 and wires in series with the compressor circuit. It protects the compressor, hoses and yes, the filter drier against excessive pressure. It also protects against low pressure, but the factory switch already does a better job than that.

The EPA Says that this type of pressure switch is a legal requirement for a correct R12 to 134a conversion, but most shops ignore it.

HAILERS

That blue/black wire puts a gnd on the a/c relay up front.

ericgrau

iTrader: (1)

Not to mention all the other things you need to do, like bearings and lubricant. I hate those conversion kits sold in stores that just have a couple fittings so you can attach your A/C to the can of R-134a. The car companies or government probably made the fittings different to keep idiots from using the wrong refrigerant . Good way to slowly destroy an A/C. Anyway you can get Freeze 12 or HC-12 (Canada only) to avoid the hassle of a conversion.

insenothepunk

OK. I do A/C work at the shop I work at. Not only can the high side head pressure detonate your dryer. It can also kill your compressor. Normally what we do about a rad fan that does come on with the ac is just wire it to a switched power source. That way there isn't a posiblility to build up too much head pressure. And as far as converting to 134. I'd say as long as you can get Freeze12 stay with it. 12 is actually much colder when the system is in proper working condition. The 134 systems I've worked on normally get down to about 45 degrees idling and about 40 going down the road. The R12 systems normally get about 40 idling and down to 30-33 going down the road. So I'll stick with R12.

Sideways7

iTrader: (7)

I have had very good success with Freeze-12 in my DD. It cools great, other than the thing when it is stopped, which happened when it had r-12, also. Plus its cheap. I get it from www.sherco-auto.com or something like that.

jackhild59

iTrader: (7)

Another glowing endorsement for Freeze12! There are not too many places that have tougher conditions for a/c than Killeen, TX. Hot and Humid.

How times do we have to say it before *they* learn?

Really, people, if you can't get the full Monty (R12), go with Freeze12!

cpubugs

jrat I have an extra stock fan and clutch if you want it, make me an offer.

RotaryResurrection

iTrader: (8)

I found this same lesson out a few months back when I was just getting my FC running after the build. I had charged it full of freze 12 but it wasn't cooling at idle. I was in the engine bay fooling around while the engine was idling with the a/c on, to see if I could see any issues. After several minutes I hear a loud noise and see freon being blown out in the engine bay, so I kill the a/c.

Get to looking around and see that there is dye/freon near the compressor on the firewall, and near the radiator at the dryer.

Come to find out the stock clutch fan wasn't moving enough air at idle to keep the pressure down (or the system cool). When pressure got too high, the "pop off valves" on the compressor and dryer opened and vented the pressure (and freon with it). Apparently these are setup to prevent compressor and dryer explosions like you had.

I had to recharge the whole thing, and after I went with the escort e-fan, not only have the pop off valves never opened again, but the system is a WORLD colder at idle than it was previously. Now, instead of being like 'what the ****, why isn't the air working" while in traffic, I am like "wow, this is actually sufficient". Granted, it never gets cold enough to make me want to turn it down from high while in traffic, but for an rx7 a/c it is truly kick ***.

Going down the road the thing gets really cold though, still not as cold as some other cars, but certainly enough that you want to turn it down to 1/2 or 2/3.

I have my fan set up to come on with the coolant thermoswitch on low speed, and the a/c relay activation on high speed. This seems to work very well so far.

imloggedin

what kind of relay are you using to do the low/high thing?

TehMonkay

iTrader: (-1)

Who really NEEDS AC?

Oh yeah, you're in AZ.

Temps here are crawling up to the low 100s, windows down/sunroof open is still sufficient enough, but the AC on my car is nice, however i will be ditching it when i do my T2 swap.