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Old 05-24-2007, 04:12 PM   #1
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Default MSPNP fan control question

I wonder...how does the MSPNP control the fans? Is the AC fan still controlled by having the AC on? Or did they set it to come on at a certain coolant temp? In other words, I wonder if I should still be thinking about wiring the two fans together, or whether it would be better to eventually play with the fan control settings in MS.

Just something to think about.
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Old 05-24-2007, 04:16 PM   #2
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the a/c grounds the circuit, so that fan should work normally.

in megatune, you set the fans to switch on at a given temp and off at a given temp.

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Old 05-24-2007, 04:23 PM   #3
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the fans essentially work the same. MS turns on the driver's side fan at a set CLT and the passenger's side fan with the ac. The only difference is you can control what temp the driver's fan comes on at, and at its default setting it comes on noticably earlier (175F?).

One of the mods on my to do list is to wire in the oem thermoswitch to the passenger side fan so it would come on either with the ac or at the oem fan trip temp (210F?). Basically that would give me a 2 stage fan system.
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Old 05-24-2007, 04:28 PM   #4
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Quote:
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the fans essentially work the same. MS turns on the driver's side fan at a set CLT and the passenger's side fan with the ac. The only difference is you can control what temp the driver's fan comes on at, and at its default setting it comes on noticably earlier (175F?).

One of the mods on my to do list is to wire in the oem thermoswitch to the passenger side fan so it would come on either with the ac or at the oem fan trip temp (210F?). Basically that would give me a 2 stage fan system.
Ben, when you get that working let me know... That's one of the FIRST things I want to do.

Jerry swapped my MS for me... so now I have an assembled one and that should jump start my turbo project fa realz.. Plus, the S4's back and it's working great... so with a reliable daily driver again, the Miata can go up on jack stands.
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Old 05-24-2007, 04:56 PM   #5
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Quote:
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Basically that would give me a 2 stage fan system.
I was hoping MS would be able to do that, but that's a decent thought also.
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Old 05-24-2007, 05:02 PM   #6
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that's an interesting idea...currently paralelled my fans turn on for about 30secs top.
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Old 05-24-2007, 05:36 PM   #7
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Ben, when you get that working let me know... That's one of the FIRST things I want to do.
That sounds good on all regards. Jerry = The man. Did they cover the A4 driveline bushing under warranty?

It's my understandign that the fans both receive +12v with the key on, and they are switched on the ground side. The thermoswitch is that plastic thing that pokes up on top of the thermostat housing, and when it gets hot enough, it completes a path to ground. So it's just a matter of swapping wires from one fan to the other. And maybe diode isolate the fan gnd wire from the MS, but I am not sure it would be necessary. It's on my punch down list; I'll get to it one day. Probably when I'm doing the intercooler sprayer or wi, or whatever it is I decide to do.

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Old 05-24-2007, 05:46 PM   #8
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Just make sure you wire it in parallel with the stock wiring, so that it is an either/or turn on. Rather, it will turn on by AC being turned on or reaching the thermoswitch grounding temp, instead of only switching on with both criterion met.

Correct me if I'm wrong though, but doesn't the ECU control the AC fan? Wasn't that one of the troubles with having a standalone MS control AC? Or was the trouble only the idle control related to the added load from AC?
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Old 05-24-2007, 05:54 PM   #9
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Yes, definately it would be a parallel path to ground, so either condition indiviudally would trigger the fan. That's why I was wondering if the MS would need a diode to isolate it from the ground path created when the thermoswitch goes to ground--it probably doesn't matter.

Fan control is pretty basic. The real problem is controlling the idle valve to keep the engine idling right when loaded up by the a/c compressor. Jerry's been working on the idle valve closed loop PID settings to get it as stock like as possible, and he's not far off now.

With the MS, turning on the A/C kind of shocks the system, and the MS follows its PID algorathyms to recover to stable idle. It is a reactive system. The factory ecu is proactive and automatically alters its control of the idle valve when ac is engaged.
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Old 05-24-2007, 10:16 PM   #10
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Originally Posted by Atlanta93LE View Post
Just make sure you wire it in parallel with the stock wiring, so that it is an either/or turn on. Rather, it will turn on by AC being turned on or reaching the thermoswitch grounding temp, instead of only switching on with both criterion met.

Correct me if I'm wrong though, but doesn't the ECU control the AC fan? Wasn't that one of the troubles with having a standalone MS control AC? Or was the trouble only the idle control related to the added load from AC?

The ECU controls the AC period-- the compressor clutch and the fan. Unless the ECU tells them to neither engage. The MSPNP takes care of this though.

As Ben said the MSPNP was designed to operate the fans very similar to stock, with the exception that the drivers side fan comes on sooner, though it's programmable so change it to whatever you want. I set it to 175F as 97c (about 206F) seemed a bit hot, and I wasn't sure I wanted to trust the manual on that one. I erred to the safe side there.

The AC fan comes on with the AC. Or if you turn on the AC before the car heats up enough to activate the drivers side fan the AC will turn both fans on.
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Old 05-24-2007, 10:17 PM   #11
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Quote:
Originally Posted by Ben View Post
Yes, definately it would be a parallel path to ground, so either condition indiviudally would trigger the fan. That's why I was wondering if the MS would need a diode to isolate it from the ground path created when the thermoswitch goes to ground--it probably doesn't matter.

Fan control is pretty basic. The real problem is controlling the idle valve to keep the engine idling right when loaded up by the a/c compressor. Jerry's been working on the idle valve closed loop PID settings to get it as stock like as possible, and he's not far off now.

With the MS, turning on the A/C kind of shocks the system, and the MS follows its PID algorathyms to recover to stable idle. It is a reactive system. The factory ecu is proactive and automatically alters its control of the idle valve when ac is engaged.
The original base map sent out with the first units did sortof OK with recovering from the shock to the system when you activate A/C, but the changes I made on your car seem to be a huge improvement Ben. I made the same changes to my car and I've been running them and it's night and day better, it recovers very quickly with no likelihood of a stall as sometimes happened before... that's going into the updated base map here soon. I'll make it available for download.
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Old 05-24-2007, 10:24 PM   #12
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so what about the regular, every day, "dual fan" mod? Will this not work with mspnp?
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Old 05-24-2007, 10:26 PM   #13
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Tell me more... what is the mod? Are you just wiring in the passengers side fan so that it runs on the same relay as the drivers side fan?

If so that would work just fine... the relay is carrying the extra load, not the MSPNP, it's still supplying the same current as before to trip the relay. No issues I can see...
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Old 05-24-2007, 10:35 PM   #14
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Yeah the common mod is to run a lead from the relay to the a/c fan to turn it on with the driver's side fan. I like my dual stage idea better.

Jerry, the current idle settings in my car work well; they're 1000% better than the original settings. Idle recovers nearly instantly when turning on the ac at a stop. The only problem is when coming to a stop, if I let in the clutch too late, the car will stall. It wants to run but I guess it doesn't have enough time to recover. If I let the clutch in before going under 3k rpm, the car recovers fine.
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Old 05-24-2007, 10:37 PM   #15
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Quote:
Originally Posted by FoundSoul View Post
Tell me more... what is the mod? Are you just wiring in the passengers side fan so that it runs on the same relay as the drivers side fan?

If so that would work just fine... the relay is carrying the extra load, not the MSPNP, it's still supplying the same current as before to trip the relay. No issues I can see...
http://www.miata.net/hakuna/parallel...%20wiring.html

thanks
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Old 05-24-2007, 10:53 PM   #16
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Originally Posted by hustler View Post
Shouldn't be a problem at all...

Quote:
Originally Posted by Ben View Post
Yeah the common mod is to run a lead from the relay to the a/c fan to turn it on with the driver's side fan. I like my dual stage idea better.

Jerry, the current idle settings in my car work well; they're 1000% better than the original settings. Idle recovers nearly instantly when turning on the ac at a stop. The only problem is when coming to a stop, if I let in the clutch too late, the car will stall. It wants to run but I guess it doesn't have enough time to recover. If I let the clutch in before going under 3k rpm, the car recovers fine.
Wait a second... did you really just say "I can't stop with my car in gear and the clutch out without stalling" ?? really?

Whenever you come by for a quick gas mileage road tune we'll look at it as see if there's more that can be done. I'll see if I can reproduce it too...
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Old 05-27-2007, 12:19 PM   #17
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Ok, here's another stupid question about fan control. I'm looking at the base msq file for the mspnp, and the boxes for fan control temp are greyed out, and set at 90F/63F on/off. Is that correct? And why are they inaccessible to change?

edit: whoops. I guess Output 2 controls the fan, and is set to come at 175F. That sounds better.
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Old 05-27-2007, 06:13 PM   #18
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Cool-- I was about to respond and see you found it
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Old 05-30-2007, 10:27 PM   #19
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Lets just say that one removes the AC compressor and condensor. Will the AC fan still come on if one pushes the AC button to the on position. I know this will turn on the blower motor if still installed, but will the condensor fan circuit still get power?
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Old 05-31-2007, 09:19 AM   #20
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As long as you don't remove the AC Relay... yep.
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