Yet another question for the brain trust.

[GH85Carrera]

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.




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?

[cashflyer]

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.

[mattdavis11]

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

[sc_rufctr]

Live with the whistling.

[mattdavis11]

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.

[scottmandue]

Originally Posted by mattdavis11

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

I love it when you talk dirty

[mattdavis11]

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.

[mattdavis11]

Originally Posted by scottmandue

i love it when you talk dirty

lol

[sc_rufctr]

Originally Posted by mattdavis11

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.

Are you serious about the water mister?

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

[Aerkuld]

Fan relay driven by the brake lights?

[dad911]

Originally Posted by mattdavis11

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.

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

[GH85Carrera]

Originally Posted by cashflyer

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.

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.

[GH85Carrera]

Originally Posted by dad911

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

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.

[bkreigsr]

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

[mattdavis11]

Originally Posted by sc_rufctr

Are you serious about the water mister?

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

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.

[mattdavis11]

Originally Posted by GH85Carrera

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.

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.

[GH85Carrera]

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.

[GH85Carrera]

Originally Posted by mattdavis11

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.

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.

[mattdavis11]

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



The one you have

[GH85Carrera]

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)