A/C and Fan Controller, what's this timing control?

[Desert Patina]

Hello all,

I'm pouring over the wiring diagrams for the 2.3L Mustangs, the 86 SVO included, and I notice a funny little circuit in the Fan Controller called "TIMING CONTROL".

The circuit, for the most part, activates a relay that simply grounds and the A/C pressure switch. I'm not sure what timing it is trying to achieve. The circuit itself is driven by the WOT (wide open throttle) on the ECU, but what and when either are open or closed, I know not.

Don't know the answer? Then feel free to enjoy this tribute to the 89,88 (t-bird),86,85 mashup my SVO is becoming while we hope for someone who can...

http://www.youtube.com/watch?v=hAMVslql9t8

[Chuck]

I believe that you are describing the WOT cutout circuit for the A/C compressor.
HTH

[Desert Patina]

Thanks Chuck. You wouldn't happen to know if the WOT circuit is closed (hot, powered) or open (dead) at wide open throttle would you?

[scenario]

would like to know the answer as well? anyone?

I am thinking it is a normally closed relay and then when the eec detects WOT it grounds the circuit to open it. This in turns breaks the power between the black/yel and the pink/lt blue wires which respectively go to the AC clutch and the AC pressure switch. The end result would be no power to the AC clutch when WOT

Please chime in and especially if I am wrong. I have been beating my head on the wall for 3 days rewiring my fan control to duplicate what the factory has but with better wiring and better relays. I have it all working but the only thing I do not have wired is the WOT wire (orange/lt blue).

[scenario]

Ok I have tested the circuit and have confirmed that the WOT cutout circuit is Normally Closed and activated by a Negative signal from the Orange/Lt Blue wire that comes from the EEC. The Negative signal occurs when you accelerate hard and will stay activated until you let off the gas pedal and after a 2 second or so delay will cancel itself re-closing the circuit.


8743

[scenario]

I made up a schematic of what I have done. Def pretty complicated but this seems to work pretty good and does what I want. Please chime in if something could be a problem. It is protected by a 30 AMP fuse on the battery wires. It uses most of the original wiring.

8744

[MikeFleming]

The EECs are programmed to provide a limited time of no AC for more burstable power - the AC does not stay off forever under WOT (15 seconds, iirc for the PE). And that short time frame is fine for street use as it's very difficult to [legally] use WOT for more than 125 seconds.

However the system does nothing to protect the AC clutch. Example: The Taurus SHO (89/90) that we used at the Bondurant School. A few years newer than the PE/SVO strategies.

The SHO engines [usually] were fuel-cut limited to 7300 RPM and the AC was cut during WOT. Problem is when one releases the throttle at 7200 RPM+ to shift, the AC clutch re-engages. We were seeing AC clutch failures in the low 2000 mile range so Ford sent a couple AC/Climate Engineers out to check it out. We eventually ended up with a larger clutch pulley and longer serp belt to slow down the shaft speeds. Helped a bit but the same issue existed - the AC was engaged at 7200 RPM as soon as the throttle was reduced for shifting. The PE does the same thing - except it's limited to 6500 RPM.

After visiting with these chaps I learned some interesting tidbits on corporate knowledge (or lack thereof). For example the v-ate GT cars, when pushed hard for 15+ minutes on-track in 100+ weather, would get really hot, like 250+F (still not boiling over, but too hot for the AC to work) - AC stops engaging when coolant is over 245. I pointed out that my SVO, with elec fan and all, was faster than the GT models and did not have ANY overheating issues in 120F+ temps. That comment was immediately met with "The SVO is a dead car, we're not going back." I showed them something that WORKS, and there was no interest whatsoever.

Interestingly it took them about 20 years to go to electric fans across the board, going back in time.

So keep in mind that using the AC at high RPMS and WOT will shorten AC clutch life.

[Bob Holmes]

Someone has AC that works?!!

[scenario]

Yes. I have a/c that works. I recharged it with R12 about 3yrs ago. Still working for now.

[MikeFleming]

Someone has AC that works?!! Slightly off-topic: My Prius has AC that works without the engine running. Timed it once and it ran (on a 115 F day) for 8:32 (8.5 minutes) without the petrol engine starting.

I looked over the engine under the hood and from underneath and there's no V- or serpentine belts. Nothing to drive AC, water pump, PS or alternator. Almost no extra parts at all.

[Under Pressure]

It's Magic!

[Under Pressure]

Mike are you using the Spal FRH relay?

[brsvo]

So you are saying the Prius runs on electricity and has a big battery, tell us something we didn't know.

[MikeFleming]

So you are saying the Prius runs on electricity and has a big battery, tell us something we didn't know. By today's standards, it's a VERY small hybrid battery, ~1.6kWh that delivers 550Volts to the hybrid system. The smallest Tesla battery is 54kWh - a bigly amount more - and they go up to 100kWh for current production cars (a yuuugely amount more).

The 12Volt battery that runs the electronics is really tiny too - about 18 Lbs worth. This battery only runs the electronicsm lights, etc. It is not used to start the SI engine.

[Under Pressure]

What about the relay you're using in the SVO?

[MikeFleming]

What about the relay you're using in the SVO? Me? I have a Bosch 30A & associated socket controlling my elec fan on the SVO.

9537

Rear-most (under the ignition coil) is the fan relay. Next two are the low and high beam headlight relays and the forward-most thingie is a 20A fuse for the fan relay power side.

It all almost fits under the stock coil cover except for the rather large bundle of wiring along the frame rail.

[Under Pressure]

I was reading people who used the Spal 16" fan were using the 30A relay were having trouble. They were told to go with the 40A relay. I don't want to be drawing 30 or 40A. I was reading the amp draw on the Spal fans. Some of them were Big. I don't want to run much over 20A on startup. I know 30 or 40A is not nominal but it could. I'm going with the 14" Spal 30102042 and the FRH relay.

[MikeFleming]

The fan I'm using (curved blade, 14" iirc) used about 13A on initial start-up and 7.5Amps running at full speed on the bench. Hence the 20A fuse. I have the model number somewhere but it's a ten+ year old model now.

I was also specific to NOT select one of the 20-30A+ units.

I have not measured the current draw with it installed in the car behind the radiator.

[Under Pressure]

The Spal 14" fan I ordered is a crurved 10 blade that draws 17 amps and flows 1864 cfm. It should work well for the A/C.

[MikeFleming]

The model fan I have is a SPAL # VA18-AP70/LL with curved blades.

9538

According to this:

http://www.universalpartsinc.com/shopping/productDetails.aspx?i=750048&c=10502

It's 16" and rated at 3000 CFM.

[Under Pressure]

I was going to go with the 16" but the amp draw was 26A I see that the one you have is the same 26A. I read different post that it was drawing too much amperage and causing problems. Not just SVO but other model engines. I'll see how this works I don't want to smoke the wires.

[MikeFleming]

I was going to go with the 16" but the amp draw was 26A I see that the one you have is the same 26A. I read different post that it was drawing too much amperage and causing problems. Not just SVO but other model engines. I'll see how this works I don't want to smoke the wires. I have absolutely no idea where they got that 26A value. Mine measured half that.

[Laredo]

I pointed out that my SVO, with elec fan and all, was faster than the GT models and did not have ANY overheating issues in 120F+ temps.....

With the stock rad / fans? Or was this after your mods?

[MikeFleming]

With the stock rad / fans? Or was this after your mods? Stock radiator and stock electric fan/shroud assembly. Time frame was summer 1990.