Exactly, pop the cover off and put an extension on the shaft.

Ok, after looking around at possible solutions here is what I came up with.

Thanks Matt for the idea.

Get another fan relay just like the first one.

http://forums.pelicanparts.com/uploa...1377805777.jpg

In this crude drawing I flipped the relay 180 degrees. Just power that new relay from the old relay using the wire that did run the fan.

The ground is the same but the sensor now it the 12 volts of the brake lights just like the old one saw the 12 volts from the compressor. The output of the second relay runs the fan.

Now the fan will only come on IF the compressor is running & the brakes are on.

The fan will come on anytime I hit the brakes if the compressor is running even if it is when approaching a corner. This is not the most elegant solution, but it will keep the fan from running while cruising down the road. It would be cool to figure out how to add a 5 to 10 second delay from the brakes coming on until the fan starts.

OK folks, will this work?

Not in a parking lot.

OK, why not?

Unless you mean while the transmission is in park and my foot is not on the brakes.

With the parking brake on, your foot will not be on the brake. The fan will not operate.

Glen, I don't think your design is bad, but I think if I were doing this, I'd add a manual switch in parallel. This way if you were stopped and parked for a while, you could switch the flip and get colder A/C. It would also work as a backup main cooling fan.

Well yea, I thought about the few very few times I am stuck at a train crossing. Now I just put it in park and park and sit. Now I will have to rest my foot on the brakes. No big deal.

Make your own pressure switch. Mount a normally open push button switch behind the grille. Make a flap out of aluminum flashing and mount it on a light hinge (like a piece of duct tape)at the top so that it will press the switch when air pressure against the aluminum flap is great enough. Wire your aux fan through the switch. Adjust the speed that it activates the switch by trimming the aluminum to the right size.
This is such a simple, elegant solution that you should figure a way to mount it on top of the hood so everyone can see it.

Simple, yes. Elegant? No.

I like the theory, but I see problems. It is windy in Oklahoma I could be sitting at a light and the wind could keep the fan from running. ;)

Buy a 12VDC on-delay relay. 5 to 10 second delay....

My thought. How does it sense and control idle? The EFI on my '88 Carrera had a microswitch that sensed when the throttle returned to idle position and activated the ICV. Very simple, just a microswitch that was pushed in by the throttle linkage. If yours has a similar switch, you could tap it. Otherwise you could just rig up a microswitch that was pushed by your throttle linkage when at idle.

Edit: here's the microswitch used on the Carrera, you can look at the diagrams to give an idea of what I'm trying to explain.

http://www.pelicanparts.com/cgi-bin/smart/more_info.cgi?pn=911-606-013-00-M100&catalog_description=&Microswitch%252C%2520%25 20%2539%2531%2531%2520Carrera%2520%2528%2531%2539% 2538%2534%252D%2538%2539%2529%2520

From what I gathered, Glen was looking for a simple solution utilizing what he has already. The way you diagrammed it is exactly the way I had in mind.

The peanut gallery here is pretty rough, but if you want to please them, refer to the other two methods.

As an a/c guy, I prefer the cooling fan pressure switch grafted into the condenser or liquid line previously mentioned. The Derale fan controller with a probe would be second.

The reason I like those two approaches better is because they are not dependent on driver input. They activate the fan automatically depending on pressure or temperature. As previously discussed, as the pressure rises, so does the temperature of the condenser.

No doubt the pressure of the condenser would be ideal. It will be a challenge to figure out what pressure point is ideal.

Haven't read all responses but had an identical problem on my 528. Replaced fan clutch and it works perfect even at long traffic lights. YMMV

We've passed up the option for a new fan clutch, a variable orifice tube and a parallel flow condenser. LOL:D

He has an electric fan, and wants to use it.:p

That compressor has a high side trigger that's supposed to CLOSE the vents to recirc when you are on MAX A/C- in other words, it supplies a ground when either you go to MAX, or high side pressure reaches a certain point- like the temps are high..

Without going complicated you can run a relay off of that, and trigger your fan. So when it's on MAX the fan activates. You can't run on MAX all day, it's not healthy (no outside air) so, at idle switch it over, let fan turn on.

Otherwise, you may need some seriously messed up electronics to make it seamless- like a VSS tapped to the cruise control sensor thing under hood.

OH- you can also go off a sensor on the upper hose, when it gets to a certain temp (215?)- fan triggers.....only way you'll hit that temp is idling.

rjp

this.

I really appreciate all the input. I really do. No doubt the pressure switch is the best way to go. BUT, that requires recovering the R-12 and opening some connections that are factory sealed from 1986. I have flushed the condenser several times over the years when I replaced a compressor. I have never removed the liquid line from the condenser to the orifice tube. I know that is not a big deal, just another place for a new leak.

I was hoping to do this the lazy man way and just add a relay. I have owned the Elky since October of 1991. It is my daily driver. I have personally driven it 280,000 miles. I know the car. The AC has operated the same way since 1991. It is not a major inconvenience, but it is annoying. My Elky operates better in every way than when factory new. With a 4 speed lockup transmission, limited slip rear end, a fuel injected 350 and numerous other improvements over the years. If my fairy god mother came along and said she could wave her magic wand and make it just like it rolled off the showroom floor I would punch her in the face and break her wand.

http://forums.pelicanparts.com/uploa...1377865570.jpg

If I take off the liquid line and take it to a local AC shop I presume I can get them to splice in a T connection for a high pressure or temp switch. I would for sure would like to have a inline filter added. There is always some minor gunk on the orifice tube every time I replace it. I guess the T connection would have a Schrader valve so I can change the pressure switch without recovering the refrigerant.

Glen, all the connections are sealed by o-rings. The factory didn't invent them and they are cheap.

Any a/c shop should be able to incorporate a tee into the liquid line to allow for a pressure switch. 7/16 or 3/8ths thread for a female pressure switch is your best bet for testing. Your accumulator has a schrader valve for the LPCO, it would be the same.

If you decide to go that route, I'd place the T on the liquid line just after the union from the condenser. If you choose to adapt an external thermo fan controller, anywhere near that union or in the condenser fins would suffice. Wrap it if you put it on the line.

I don't think you should be having this problem with an R12 system though. Having admitted that your vent temps are 40 degrees with an axillary fan tells me four things, 1) the compressor is weak (hope it's not a compressor works), 2) too much oil in the system, 3) bad fan clutch, 4) external fins on condenser won't allow air flow.

Your system should blow in the 20's all day long.

Another in line filter (orifice tube is one) just creates another possible restriction, but if you insist, I have one for an R4 that mates to the back of the compressor before the hose assembly.

Edit: five things, 5) overcharged.

I think that most here are over thinking a solution with-out finding more about the cause.

1) Identify whether the car was converted to R134 when the previous major A/C work was done. If it has therin lies part of the source of the issue; deviation from stock designed components. R134 is less efficient and runs significantly higher high side pressures than R12. If indeed it has been and all below items addressed a higher effficiency condenser may be needed.

2) Dirty / clogged condenser fins. You would be so suprised if you removed the grill for access to the condenser, then liberally applied a good cleaner like simple green then power wash and watch the debris hit the ground. What a huge difference it makes in the high side pressure

3) Clutch fan worn out. No airflow for sure will make this happen everytime. From your description of the cars condition and mileage sounds as replacement is no brainer.

4) System is slightly over charged. Pressure = heat. Depending on the vehicle it could be just slightly overcharged but the difference in cooling would be substantial to point of activating the high pressure cut-out switch (if equipped) to cut the compressor when pressures get too high.

If it was the fan clutch, wouldn't he also see the temp rise on the cooling water system? Several of my older cars had the hydraulic fan clutch and they definitely go bad.

The center dashboard vent temps with the system on MAX high fan is 40 degree air and a lot of it. It gets uncomfortably cold after 10 minutes blowing on my face. I would not want it any colder. I need to dig out my IR thermometer and read the evaporator temp. The entire accumulator will get cold enough to be covered in condensation while it is sitting in the engine compartment in 15 minutes of drive time. It blew ice cold air last weekend on a 100 mile trip down the highway at 75 MPH. Without my new fan while sitting at a long red light the vent temps go up rapidly.

The fan clutch will go into lockup if I wait at the light for long. I was careful with the oil and the pressures when I replaced the last compressor. The systems is great except at idle. It really has been that way for 22 years.

I remember the day I bought it I took it for a test drive. I loved the AC since at that time I had a non AC 914. I left it running and popped the hood to watch it idle and see what it would do. The engine got warm since it had the stock 2 core radiator. The AC was blowing much warmer. A quick drive down the street and it was back to cold. The only instruments at the time was the speedo and fuel gauge. I replaced that with the factory gauge package back in the 90s sometime.

I have replaced the fan clutch at least twice over the years. There is not much on the vehicle I have not worked on over the years.

I will talk to the AC shop and see what they have for a T connection for the liquid line. I will have to get motivated to want to R&R the system to get the pressure switch in place. That might wait until the next time the compressor dies.

If he had a stock radiator, but he has a larger radiator, a 3 or 4 row core I presume.

If the inside temp rises that fast, you have a vacuum leak, or the heater valve and or blend doors don't work properly. Both are vacuum operated. Sounds to me like the heater core is fighting the evaporator, raising the low side pressure.

Normally, if you can't bring down the low, the high won't come down as well. However, you can bring down the high with a fan to make the evap happier on the low. Using a water hose on the condenser, or a fan in your case, can help the system find an equilibrium where it's happy. This is what you are doing now.

Focus on the low side now.

The engine was replaced 20,000 miles ago. All new rubber hoses and vacuum connections. There is no sign of a vacuum leak. I had periods in the past of vacuum leaks. I know the signs.

I went and bought a new fan clutch today. The old one has been on there a long time. I will see if it helps. If I hear it lock up more I will know the old one was work out than I thought.

I think the low pressure switch turns the compressor off at 35 PSI but it might be 30. It sure works now.

Grab the fan and have someone fire up the motor. If you can hold on to the fan, bounce the blades around, then clutch is no good.

The LPCO should not have a cut out that high, maybe 10-15.

Replacing the motor doesn't much matter when the problem lies within the cabin.

I'd look to see if you are losing vacuum at the back of the control head.

I went ahead and replaced the fan clutch yesterday. It is a real simple task, and pretty cheap. It has not been hot yet so I don't know if that made any difference at all.

The system is still R-12 and is the typical GM CCOT style system. The low pressure switch is attached to the accumulator and I will have to check the specs but as I remember it cuts off the compressor in the 30 to 35 PSI.

I did get the second relay installed yesterday. Now the fan will ONLY come on when the compressor is running and the brakes are on. I still need to find a relay with a 10 second delay. Swapping the relay should be a piece of cake. With the delay relay it will keep the fan from running every time I hit the brakes to slow for a corner or traffic.

No doubt the best option will be to graft in a pressure-temperature switch in the liquid line from the condenser. Obviously that requires opening the system. My dual relay jury rig should achieve my goal of running the fan while at a light, but not while motoring down the road. I am sure my alternator will appreciate the lightened load.

For the few if any folks that are curious how things turned out on this project:

I finally found an affordable (17 bucks) weatherproof automotive 10 second delay relay. I could find lots of expensive ones that were close to or more than $80. :eek:

Now while driving along the fan never comes on. If I use the brakes to slow down to change lanes the fan does not come on. Only after 10 seconds of braking when the compressor is running does the cooling fan run. :cool:

We did had have a nice hot 95 degree day the other day. I took the wife to dinner and the traffic was heavy. Lots of sitting at long lights. The AC was blowing cold and the engine temp even stayed lower that before.

Overall I am real happy with the results.

Thanks all that made suggestions and especially to Matt Davis.

Well done Glen. Very creative solution to the problem.