ULTM8Z

So I'm looking for a way to have the condenser fan turn off when I'm at speed, like how the 7730 ECM does it with the main radiator fans. I use a condenser fan to help with efficiency on the A/C and it does help significantly when at idle and low vehicle speeds. Even in this crazy heat wave, the system blows extremely cold air.

As of now, the condenser fan comes on with the A/C clutch and remains on until I turn off the A/C. But it'd be nice if I could have fan disable once the car is up to a decent speed.

As far as I can tell, in $8D, the only speed-related cut-offs are associated with the radiator fans and the fuel pump.

I'm currently using both cooling fan circuits to run my two speed Ford Taurus fan.

Is there anything in the 7730 that's speed related that I can take advantage of?

Is there something I can buy that's stand-alone that I can wire in to the condenser fan relay to turn the relay off at a certain vehicle speed?

Btw, this is in a 2nd gen with an aftermarket AC system running independent of the ECM.

Fast355

iTrader: (2)

Just use a trinary switch like I did ob my G20. Will only run the fan as needed for pressure control.

ULTM8Z

Interesting,

The other thing I was thinking about was mapping the condenser fan relay switched ground to the same switched ground as the ECM primary fan circuit. The speed cutoff for the primary fan circuit will then apply to the condenser fan.

I figure that around town at low speeds on a hot day when I have to run the A/C, the primary fan is typically going to be mostly on to keep the engine cool. So the ground for the condenser fan will be available through the primary fan relay when I turn the A/C on. When I'm at speed and don't need the condenser fan anymore, the ECM will have already disabled the primary fan anyway,

Fast355

iTrader: (2)

7730 has two outputs for fans as well as one for the AC compressor.

RBob

iTrader: (1)

Z, I too noticed this a number of years ago when going through the $8D code (fans always on with A/C compressor active). And was surprised. It wasn't something that I expected.

(edit: this isn't correct, see post #29 further down. It is the engine temperature that will keep the fan(s) on.)

But then again, with both the y and f body cars being grill air challenged, maybe that is why.

I recently took a look at the fan code, and as before, would need to rewrite sections of it to have a MPH shut off.

And... did come up with a non-code idea. A flap switch. That is a micro-switch that is activated by a flapper. Placed behind the grill, and activated by the flow of air through the grill, the switch can be set up to interrupt the signal to the fan relay(s).

Not the most elegant solution, but something to keep in mind and expand upon.

RBob.

ULTM8Z

Lol... the brilliant simplicity of it.

Certainly an interesting idea. I guess I'd have to calibrate it to an airspeed that matches the vehicle speed. I do have an hand-held anemometer I could play around with.

Then wire up a temporary indicator light into the cabin to let me know when the fan is on or off to see if the calibration was correct. Then when calibration is verified, remove the indicator light.

Hmmmm.....

I also did notice that TunerPro has a compressor shut off speed (something I didn't notice earlier), along with a shut-off based on %TPS and coolant temp.

The ECM isn't controlling my compressor even though it receives a signal that I've requested A/C. I mapped my aftermarket A/C control to deliver a signal to the ECM to at least have the main cooling fans be based on A/C request.

So I could potentially pull a wire and map to the ECM for hte A/C clutch turn on. So I'd use the clutch enable circuit to run run the condenser fan, which would then shut off the condenser fan at whatever speed I select.

ULTM8Z

Well, looks like my A/C clutch idea is a bust. Even though TP is showing parameters that seem to indicate ECM control over the A/C clutch, I'm not seeing anything on the 7730 wiring diagram that has a provision for that. The A/C clutch appears to be controlled only by the HVAC switch and the ECM only gets a signal that it's on.

Unless there's something I'm missing.

The other option I thought of is TCC clutch circuit. My transmission is also independent of the ECM.

RBob

iTrader: (1)

You are, GM used two different methods of A/C and fan control. One for the f-body and another for the y-body. Naturally the y-body uses a different but equivalent ECM. And controls both fans and the A/C via the ECM.

Check that out, your solution may bear out. See the QuadPlugEcm file for the pin-out between the '7727 and '7730.

RBob.

ULTM8Z

RBob, Awesome....I think you have me headed in the right direction...

According to a wiring diagram I found for a 1990 Corvette

https://ww2-secure.justanswer.com/up...rl_diagram.gif

The A/C clutch control is on Y13 (though I think they meant A13)

https://ww2-secure.justanswer.com/up...7_020752_1.gif

If I go to the QuadPlugEcm file, https://pcmhacking.net/ludis/quadplugecm.html , it's showing this connects to F3 on a 7730.

When I go to the 7730 pinouts, F3 isn't populated (as you alluded to).

I was going through my EFI harness and remembered that I don't have EGR on my engine. So all I have to do is re-pin one of the EGR wires over to F3 and then I can use that to drive the relay switching circuit. That'll save me from having to pull a new wire.

A13 on the 7727 appears to be an ECM grounding circuit for the A/C clutch control relay if I'm reading the schematic correctly. So when my ECM detects my A/C signal request at C9 on the 7730, it should provide a ground out of F3 for the condenser fan relay so long as my vehicle speed is below what I program for the cutoff.

Fast355

iTrader: (2)

As I said before, I used fan 1 and fan 2 outputs. At ~40 mph my fans turned off. Slow down and they turned back on.

ULTM8Z

I'm already doing that with my two speed fan. I have the ECM controlling both speeds using the fan 1 and fan 2 output.

What I'm looking to do is have my A/C condenser fan be under ECM control as well at least for the speed cutoff (it comes on whenever the A/C is turned on).

RBob

iTrader: (1)

C9 is the A/C status input to the ECM. Need to ground pin D3 to request the A/C compressor relay output.

RBob.

Fast355

iTrader: (2)

So you are adding a 3rd fan. Gotcha. Could tie it into fan 1.

ULTM8Z

Got it (I think).

I'm currently wired up per the 7730 wiring diagram https://www.thirdgen.org/forums/atta...fan-wiring.jpg

When I turn on my A/C, I have a 12V wire from my clutch circuit mapped into C9 to tell the ECM that A/C is active. Looks like that maps to C17 which also appears to be the A/C status on the 7727. So I should have that covered already.

D3 on 7730 maps to B15 on 7727, which is (as you said) AC request input coming in from the HVAC control. So if I permanently ground D3, the ECM should permanently enable the ground for the condenser fan at F3 (A13 on 7727). Since the actual on/off for the condenser fan is controlled by my HVAC control, the ground will be permanent available whenever I turn on the A/C.

The speed cut-off would then terminate the ground output at F3, thereby shutting off the condenser fan relay.

If that's not correct, I'd probably have to put in another relay that would provide a switched ground to go to D3. The A/C clutch circuit from my HVAC control would activate that relay to send a ground signal to D3.

ULTM8Z

I thought about that in an earlier post. But I think RBob's approach is a more elegant solution... I get true independent condenser fan control that's directly tied into when the A/C is on or off.

Fast355

iTrader: (2)

Running GM factory AC on my old 83, I tied my condensor fan relay into the high blower relay signal. It was an aftermarket cooling fan wiring kit. The only time it had high ac pressure was when the interior was hot and the blower was on high fan speed. I also put an aftermarket temperture switch in the passenger side head. The fan only ran when the engine was at about 200°F or the ac was on high fan speed. Once I hit the highway and the interior cooled off and I dropped the fan speed the condensor fan shut off.

ULTM8Z

So RBob, i wouldnt think this would be the case, but if the ECM thinks the AC is always on would there be a problem running it like that?

It would be the result of me permanently grounding the AC request wire for the reasons I explained a couple of posts above.

RBob

iTrader: (1)

Probably no ill affects. The A/C request is just that, a request. Being a cycling system the A/C Status input is what the ECM uses to know whether the compressor is engaged.

I didn't look at the code, but you would need to do either that or just try grounding the A/C request and see what happens.

RBob.

ULTM8Z

Ok, cool thanks.

Yeah, I'll probably just try grounding it and see what happens.

ULTM8Z

Grounding D3 worked. I see A/C signal requested in the datastream. Sweet!

Now just need to repin the EGR wire over to F3 and splice it into the relay circuit.

Fast355

iTrader: (2)

The only problem I see with leaving it permenately in AC request is that it will not learn the IAC steps for the ac load compensation when the ac is enabled. That was one of the reasons I added an A/C relay on my old G20 van years ago. It would nearly stall when the compressor kicked on. I added the relay and moved the request signal to the output of the cycling switch (mine was +12VDC) and the ECM could then do its magic with the IAC then enable the compressor. I had to move the request signal on the cycling switch because the signal was tied into the dash switch side being that it was the wire for the original throttle kicker solenoid on the Q-Jet. After it was wired correctly and the compressor was cycled a few times the ECM learned the compressor load and the transition was seamless. Turn the ac on and the idle speed was the rock of gibralter steady, when it cycled the IAC opened and closed even rolling down the road. You could physically not feel any change in the engines output at idle or part-throttle or WOT for that matter since the ECM cut the compressor at WOT. I have had to add an ac relay and proper ac request signal on several LS swaps as well because of this. Nothing like starting a 100K LS swapped car, the ac kicks on and it stalls. My 97 Express running a 2005 DBC P59 is wired correctly as well. That PCM even pulls timing when the compressor cycles off at highway speeds to prevent the feeling of the compressor torque spikes.

ULTM8Z

Hmmm.... never really had that issue. Maybe my mild cam isn't as susceptible to that. But when the compressor kicks on its barely noticeable.

ULTM8Z

Ok, so I have everything wired up... A/C disable set to 10 mph just for a test to drive up the street. Indicator light temporarily hooked up in parallel with the condenser fan.

The condenser fan evidently isn't turning off as the light doesn't turn off. In corroboration with that, the datastream is indicating that the ECM is not turning the A/C clutch off when I'm over 10 mph.

To recap, here's how I have it wired up...

A/C request input => 7730 C19 => 7727 C17 => Receives 12V when I have the A/C turned on.

A/C on input (feedback from A/C relay that A/C is clutch relay is engaged) => 7730 D3 => 7727 B15 => I permanently grounded it

A/C clutch enable => 7730 F3 => 7727 A13 => Wired to the condenser fan relay


My guess is the A/C on input can't be permanently grounded. The ECM thinks the clutch relay is always on.

I'm probably going to have to put on a separate relay that will send a ground back to the ECM when the clutch relay enables.

ULTM8Z

Actually, looking at the schematic...

It looks more like the A/C on input should be a 12V signal back to the ECM at D3.

I'll try re-wiring it and see what happens.

ULTM8Z

Ok, so now I'm finding out that I'm getting a 12V output from D3. It's supposed receive a 12V input from the HVAC switch. Two different ECM's doing the same thing.

Ugh... whatever... this is getting to be too much headache for not enough benefit... lol...

Just going to go back to completely independent operation of A/C from the ECM... So the little condenser fan stays on all the time with the A/C... it's not the end of the world.

Unless someone knows what's going on here...

RBob

iTrader: (1)

Pin D3 ('7730) is an input. There is a 1.2K pull up to IGN+, which is what you are seeing and thinking that it is an output. It isn't, it is an input.

If you want to see the y-body A/C & fan control via the '7730 pin out:

EBL_P4_Drawings_Images/pg5of7.jpg

RBob.

ULTM8Z

Thanks much! This schematic appears to be the clearest and most concise one I've seen so far. Hallelujah...lol

So if I'm reading this correctly, the D3 is in fact expecting a ground signal. On the 7727 pinout diagram that I pulled from online, it looks like D3 is getting a 12V signal... but when I probed D3 and found it already essentially has battery voltage on it, that was confusing.

F3 and C9 I have wired correctly.

Maybe I'll give it one more try. My HVAC control puts out a 12V to the compressor. So I guess I can initially just try manually grounding D3 and see how the ECM commands things. If it works, I can probably wire in another relay off that 12V HVAC switch that will then provide a switched ground source to D3.

ULTM8Z

Ok. so the good news is the ECM is reporting the A/C requested and clutch engaged correctly when I turn on the A/C, as well as not requested and disengaged when I turn it off. So it seems like everything is finally wired up correctly.

The bad news is that the it doesn't seem to be automatically disengaging when I get to the set cutoff speed. The ECM (via the datalogger) doesn't report the clutch disengaged when I hit the cutoff speed. I also have an indicator light temporarly wired in parallel with the condenser fan so I know when it is on/off as a way to physically validate what the datalogger is telling me.

To recap, I have the A/C clutch engage circuit being utilized for the A/C condenser fan so the fan can shut off above a certain speed (the same way the main radiator fans do). Since my aftermarket A/C system works completely independently from the ECM, I was looking for an unused ECM circuit that would disengage as a function of vehicle speed and the previously unused A/C clutch engage circuit from the Y-body 7727 seemed to have that available in it's sister 7730 ECM.

I also unchecked the flag for the Fan switch normally open (which I think is what your schematic is saying to do). I currently have the cutoff speed set at 40 mph, but yeah even at freeway speeds the indicator light and the datalogger are showing that the condenser fan is still running.

Is there something else I need to adjust in the calibration?

EDIT: Started looking through the ANHT HAC file... Search on "A/C" and you get literally 313 references... lol. Hopefully there's something in there that might explain what's going on. But the code is over my head for the most part.

http://www.diy-efi.org/gmecm/papers/anht_hac.pdf

RBob

iTrader: (1)

OK, I got this backwards. As Fast355 stated in post #10, there is a A/C active fan off MPH setting. As long as the engine temperature is good, the fan(s) will turn on & off with A/C active/inactive and the vehicle going above and below a programmable MPH setting.

Where the fans do stay ON, is due to the engine coolant being over the set point. There is no MPH cutoff on this. If the engine coolant temperature is over the fan on set point, the MPH doesn't matter. The ECM will keep the fan(s) on.

This is the part that surprised me.

Note that the f-body setups, the ECM only controls the primary fan. Where-as the y-body cars the ECM controls both fans.

And, it is easy to change the f-body setup to control both fans by adding a simple wire between ECM harness pins D12 (splice into), and F8 (open, add terminal).

RBob.

ULTM8Z

There may be a misunderstanding on what I'm after...

Right now the ECM controls the two-speed radiator fan. I'm using the fan 1 circuit for the low speed and the fan 2 circuit for the high speed. I did the Y-body wiring update for the 2nd fan a while ago. Those turn on and off with speed and coolant temp as you said.

However, I also have another fan that's mounted to the A/C condenser, completely separate from the ECM. I had that fun running off the A/C system which is aftermarket and also completely separate from the ECM. It only comes on when I turn on the A/C and will turn off when I turn off the A/C. But, without ECM control, it'll stay on now matter how fast I'm driving.

So the goal here was to utilize the unused A/C clutch circuit in the ECM to drive the condenser fan such that I can get the ECM to control that fan as well, and turn the condenser fan off when I'm at driving at say 35-40 mph. Since there's a parameter that can be set to turn the A/C clutch off at a certain MPH, it seemed like a convenient option.

So yeah, I'm leaving the existing radiatior fan 1 and 2 circuits alone. But trying to drive the condenser fan off the unused A/C clutch circuit in the ECM.

What's happening now is that I have the system wired up, but the ECM is not turning off the condenser fan when I hit the pre-programmed speed. I also unchecked the flag for the Fan switch normally open (which I think is what your schematic is saying to do for driving the A/C clutch in the 7749 config)

???

iTrader: (5)

old thread I know, but I read of a guy years ago that put the condense fan on the brake light switch. that way stopped at red lights it was on. but not needed any other time.