Yet another question for the brain trust.
 

Once again I have a question that likely has a simple solution that I can’t figure out on my own. My trusty daily driver El Camino has a great air conditioner. It will blow a lot of 40 degree air on a 100 degree day. That is as long as you are moving. Once I come to a stop at one of the many LONG red lights the cold air becomes not so cold. I added a 12 inch Spal pusher fan right in front of the condenser which sits right in front of the radiator. The water temp is not the issue it is the lack of air to the condenser. The fan makes a huge difference and the air stays cold now. All of this is because I like to tinker and make things better than GM did in the 80s. Sometimes that is not hard at all.

http://forums.pelicanparts.com/uploa...1377267355.jpg


The point of the post is the fan is not needed at all if I am moving more than 25 MPH. The fan only runs when the compressor runs so it cycles on and off a lot under light AC loads. It starts to whistle at speeds above 40 MPH. It is not doing anything at that speed and is unnecessary. If the fan is not running it does not whistle at speed.

My goal is to figure out a way to make the fan run only when stopped or the car is moving below 10 MPH. It is not a temperature thing. The water temp is fine with the big radiator I have. The AC system is typical GM orifice tube system. I can’t see using a pressure sensor to run the fan. Right now it reads the 12 volt signal from the compressor clutch to pull a relay to start the fan. It cycles perfectly with the compressor.

There is a speed sensor on the speedometer that the fuel injection system reads but I have no idea how to tap into that signal. Throwing away that carburetor and going to fuel injection is the best thing I ever did to the Elky.

I could put in a manual toggle switch that activates the system only when needed but that is just not an elegant solution. Every time I come to a light flipping a switch instead of watching traffic just does not make sense. I can just ignore the fan noise and it does not hurt anything for it to run.

Any suggestions?

What year is the El ?
Post 1996 they have OBDII and you can pull a speed signal from that. Of course, you will need some sort of computer gizmo to take that data and say, "If speed > x, then fan is condition 0."

If pre-OBD, then get a GPS sensor and do the same thing.

Or take the signal from your TPS. If throttle value > X, then fan is condition 0.

Dump the electric fan, get a parallel flow condenser, a new fan clutch and a variable orifice tube.

Live with the whistling. ;)

Another solution would be to keep what you have, but tie in the fan to a temperature switch, which activates the fan by reading condenser temps.

I love it when you talk dirty

Another option would be to add a water misting system in place of the fan, or with it. What you could do is get a pump, a reservoir, and nozzles to have a condenser mister activate when you are stopped. Tie it into the brake light switch. Or tie the fan into the brake light switch to activate the fan.

It is an automatic if IIRC.

lol :D

Are you serious about the water mister? :confused:

Although I like the idea of using the brake light switch. Probably the simplest way.

Fan relay driven by the brake lights?

This. with one of these to control relay: 12V Digital LCD Thermostat Temperature Regulator Controller Aquarium Fish Tank N | eBay

It is a 1986. They quit making them in 1987. No OBDII. The GPS sensor sound like a fun Rube Goldberg option. I might be about to tap the speed sensor signal from the ALDL connector. That is what they called the connector back then.

The TPS is a good idea as well. I will have to dig into the Fuel Injection system to figure out the speed sensor or throttle sensor.

That is a neat gadget as well. It would have to work at temps aroud 40 to 50. The one problem I see with that is on mild days when the AC is on a low setting the fan would kick on when it is not really needed. I don't like 40 degree air blowing on me if it is just 75 and sunny out.

could you rig up a micro switch at the base of the throttle (carb?) -? - get fancy and thread the bracket so the switch is adjustable ala MFI.
My 77 Buick 3.8 L had a similiar switch that would shut the compressor off at full throttle. (for that extra umphh)
Bill K

It was just an idea, not a very good one knowing he probably won't want to fill the reservoir when needed, but it will work.

He's fighting an issue with climbing high side pressures because there is little air flow across the condenser at idle. Not trying to be a smart ass, it is what it is.

Do you have a variable orifice tube already? Or is it just the one recommended for the R4 system?

Have seen good results out of them with an oe condenser and good fan clutch.

No no, it would only kick the fan in when the condenser temps rise above a certain temperature.

If you don't like 40 degrees at 75 ambient, slide the temperature lever on the control unit towards the middle.

The AC system is 100% stock. I replaced the 27 year old rubber hoses when I replaced the compressor the last time. I took the hoses to a local AC shop and they used my ends and replaced the rubber parts. The evaporator was replaced when it developed a leak about 12 years ago. The accumulator gets replaced every time I open the system.

The fan clutch is probably due another replacement. After 20 years of driving it over 300,000 miles I can't blame the previous owner for much. ;)

The AC has done this since I first got the car. It still has a better system than my 85 Carrera with 4 condensers. I just want a AC like my wife's 2008 Infinity. That is never going to happen.

The orifice tube is the original stock system. I really need to figure out how to engineer a pre-filter in front of the orifice tube. I am not familiar with variable orifice tubes.

Wow. For 30 cents, I replace the orifice tube anytime the system is open, typically skipping the accumulator depending on the time frame of how long it's open. But that's not the problem. Fluctuation in pressure is, and that, you already know because you have a fan trying to pull down the high side.

Variable orifice tubes will do just as they are named, they will allow more or less refrigerant and oil to pass through and automatically adjust under certain pressure conditions. It's not an add on, it replaces the orifice tube.

The orifice tube is a filter and expansion valve in one little bitty piece.

Variable

http://t3.gstatic.com/images?q=tbn:A...9LUmirHmvISExQ

The one you have
http://t0.gstatic.com/images?q=tbn:A...QY7LFt8Dl0w263

Usually the only time I open the system is after another compressor dies. I use my AC a lot. A compressor last about 90,000 miles. The orifice tube is always replaced. For less than a buck it is a no brainer. Most of the time there is some gunk on the old one. The accumulator is replaced only if the compressor is replaced.

I did find this filter that I may order and have on hand for the next system purge.

A/C IN LINE FILTER

Hopefully the current compressor will last another few years.

The suggestion I like the most is to tie the fan to the brake lights. Now I need to figure out how to tie the brake light switch into a relay that will signal the fan to come on if the compressor is running.

So if the AC compressor is running and the brakes are pressed the fan runs. If either the compressor is not on, or the brakes are not on the fan does not run.

This is my current setup (no pun intended)

http://forums.pelicanparts.com/uploa...1377281719.jpg

It IS a temperature thing though. ...but not temperature of the engine, temperature of the output!

So why not use a temperature switch on the output of the AC itself. It the AC is running and the output is above, say 55 degrees, then turn the fan on?

I thought about that. It is a good suggestion. But what about the times in spring and fall when the AC is mostly de-humidifying the air and not working very hard. The temp will get that high and the fan comes on. That will not hurt anything but it is not needed then for sure.

I am one of the folks that only rolls down my window to talk to someone like a toll booth attendant or something like that. I don't ever ride around with the window open even on a perfect day. I have too many allergies. I drove an un air conditioned 914 for over 20 years. I have had a lifetime of open air driving. BTDT. I an't gong back. Either my heater is on or the AC is on.

A pressure switch might work if I could calibrate it to the high pressures, but that is going to be a challenge to graft into the system. The brake pedal seems to be the best suggestion so far.

Not a bad idea, but the condenser is closer and easier to adapt a thermal sensor into the system he already has in place.

It's all about the delta T from condenser input and output, not the evaporator or vent temps, although 40 degrees at 100 ambient is a bit high for my liking. Should be down in the 20's

The 40 degree temp is the air temp with the fan on MAX blow. If I lower the fan speed it gets Down to 32 degrees air temp from the center vents.

Drop the pressures a tad so where it nearly ices up the evaporator. LOL.

Naw, it's cold enough.

Did you integrate a cabin air filter to rid yourself of outside pollens?

Flow switch.

Air Flow Switch for DC/ AC Voltage Supplies (Type 3201.-/3204.-)

These are factory set to 3m/s or about 10 feet per second. You will need to duct some air or place it in an area sure to sense flow.

Now he has to go with a 24v DC supply. I like where this is going.

Actually, if he is willing to DIY, he could build his own flow switch.

Use a piece hard metal dryer duct with a flapper at the end. Put a switch in the duct so that the flap activates it when there is no airflow. You will probably need to add a weight to the flap to get it to activate the switch. I would put a relay inline, since these types of switches are not really well suited for lots of current.

http://ecx.images-amazon.com/images/...6L._SX385_.jpg

Now we're jumping the shark! Bout time!

James I like it! I would have NEVER thought of that.

Now I gotta figure out how big that is and where to mount it. It will have to be hidden fairly well. I love the out of the box thinking. It would be something to talk about when I show my boring stock 350 engine. As Spock might say Fascinating.

I will look into that as well as the speed sensor idea.

I was thinking about the speed sensor idea. I know that I can hook my laptop up to the ALDL and monitor output from the fuel injection computer. It shows the speed, and throttle position and O2 sensor readings. It also know what gear the transmission is in and other values.

Nothing can be changed from the fixed program, but you can see what is going on. I really need a motor-head 18 year old programming geek to figure out how to integrate all the readings just to turn a fan on and off. ;)

I could not find a price for that flow meter. It is 100 bucks or 1000 bucks? That does make a difference. ;) Where did you find the metal vent? I need one of those for the house. Or crazy dog decided the plastic driver vents are tasty and destroys one about every two months.

5 prong relay. Compressor closes one portion, then the brakes close the loop, energizing the relay to turn the fan on.

Just go off the TPS.

That is very logical. I just need to figure out how do do that.

We're going to need a bigger ramp: variable pitch propeller | eBay

Going to then have to figure out how to get more output to make that relay work. TPS range on a TBI motor is said to be .5v to 5v DC at WOT.

Hmm...my Audi has a visco clutch fan + electric fan that only kicks in when gas pressure is too high = cooling flow is bad. Can't you use something similar?

I don't think cheese meant to use the TPS voltage, just the movement to activate a switch. Problem with this is having the fan run on cool days and cold nights at idle.

RB's idea sounds pretty good except for the same problem. Same with the GPS. The solution can't have anything to do with speed, motion or air flow, IMHO.

The orifice sounds interesting, but even with the explanation I don't completely understand if it will do what Glen needs to do, activate a fan in hot conditions when stopped. The in-duct temp sensor might be tardy in operating the fan and shutting it down. He could be doing 40 before the duct temps fell.

That's why he asked here because if it were easy, he'd have done it already.

I guess I'd install a horn button within reach and use the horn ring to run the fan. Not going to help the valet. :D

I would not touch any reference voltages with the ecu. I like the brake light switch recommendation as it's 12v and not ecu/tune impacting at all. Just put the relay in series with the clutch feed so only when ac is running. Cost is near nil.

You could also use a shift light with programmable 12v output to kick a relay as well.