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 Post subject: Radiator fan "Modes" -- how to relate to fan operation?
PostPosted: Sat Dec 10, 2016 6:29 pm 
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The ROM for my 2007, 2.5, non-turbo (E2UG001B) has tables related to radiator fan "modes". There's three mode tables based on ECT, and one based on vehicle speed. (see attached).

I believe that they combine in some way to determine when the ECM will turn the fans on, and at what speed (i.e., off, both fans slow, both fans high). But I don't understand how the ECM decides which mode to use, and hope someone here can explain the function.

For example, if I'm reading the tables correctly, it appears that in the Mode A, as the ECT reaches 201.2 F, the fans will turn on in M1 (slow speed), and if the ECT rises further to 212 F, the fans will be switched M2 (high speed). On the decreasing side, as the ECT comes down to 203 F, the fans will switch back to M1, and at 197.6 F, they will turn off (M0).

However, in Mode B, and Mode C, the first time the fans would come on is at 210.2 F, and M2 would be implemented only at 217.4 F. This seems to be significantly higher than Mode A. Why the difference?

Vehicle speed seems to be related, based on the fourth table in the attached screen shot. How does this table relate to the choice of mode?

My quest to better understand the fan control was started because some time back I noticed the fans coming on with the ECT at around 203 F, but more recently, I noticed that the fans were not being activated until the ECT was around 212 F. This seems to correspond to the ECT-based mode tables, but why the change? What determines which table is used?

I looked for comparison start/stop data in http://www.subaruoutback.org/forums/66- ... -turn.html, but so far no definitive info.

The Table Properties has some information, but do go as far as identifying the relationships.

Anyone?


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 Post subject: Re: Radiator fan "Modes" -- how to relate to fan operation?
PostPosted: Sun Dec 11, 2016 1:13 pm 
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Check this it might help.

Attachment:
Screenshot_2016-12-11-21-03-16.png


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 Post subject: Re: Radiator fan "Modes" -- how to relate to fan operation?
PostPosted: Sun Dec 11, 2016 6:21 pm 
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Yes, I'm familiar with those Subaru fan operation tables from the FSMs. The one for my 07 is attached -- it's slightly different than the one you posted.

If I read it correctly, when the car is stationary or moving very slowly, with the ECT below 203 F (95 C), the fans are off. If the ECT rises to 205 F (96 C), the fans should come on at low speed, and remain there as long as the ECT is between 205 F and 210 F (99 C). If the temperature goes higher to 212 F (100 C) or more the fans should be at high speed. That corresponds to the "Mode A" table in the ROM tables attachment above.

However, as noted in my SubaruOutback.org thread (linked above), while Mode A-type operation was observed some time ago, more recently the fans come on at their slow speed only at around 212 F (100 C). That seems to correspond to Mode B (or C).

Although the FSM fan operation table makes no reference to Mode B-range temperatures, the ROM certainly does. Consequently, my question: What criteria would cause the ECM to switch from Mode A to Mode B (or C) control of the fans, where, with the latter, the engine would be allowed to run notably hotter than in Mode A?


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 Post subject: Re: Radiator fan "Modes" -- how to relate to fan operation?
PostPosted: Sun Dec 11, 2016 11:46 pm 
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Your car is slightly different, I have 2 Mode tables that correspond to Fan 1 and Fan2. both are relative to vehicle speed, temperature and AC switch.

Yours I guess Mode A = Fan1, Mode B= Fan2, Mode C = Both Fans

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 Post subject: Re: Radiator fan "Modes" -- how to relate to fan operation?
PostPosted: Mon Dec 12, 2016 8:49 am 
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welaish wrote:
Your car is slightly different, I have 2 Mode tables that correspond to Fan 1 and Fan2. both are relative to vehicle speed, temperature and AC switch.

Yours I guess Mode A = Fan1, Mode B= Fan2, Mode C = Both Fans


What year/model do you have?

In my case (07 Outback, 2.5, non-turbo) the fans are controlled by the ECM through a set of relays. The first three tables in my attachment in post #1 relate to different temperatures at which the fans will be Off (M0), Low Speed (M1), or High Speed (M2). In all instances, both fan motors are supposed to run together, at the same speed.

I'm looking at only when the car is not moving (or moving very slowly) and the AC is off, so that coolant temperature would appear to be the only determinant. What I don't understand is why there would be more than one set of temperatures at which the fans will be turned on or off, and how the ECM selects which set of temperature trigger points to use.


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 Post subject: Re: Radiator fan "Modes" -- how to relate to fan operation?
PostPosted: Mon Dec 12, 2016 8:20 pm 
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I have 2012 STI.

What you can do is to log Coolant, Vehichle speed, and fan relay switch 1 and 2.

And take the car for drive on highway, traffic with AC on and AC off again and check when the fans are kicking in.

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 Post subject: Re: Radiator fan "Modes" -- how to relate to fan operation?
PostPosted: Mon Dec 12, 2016 10:09 pm 
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welaish wrote:
I have 2012 STI.

What you can do is to log Coolant, Vehichle speed, and fan relay switch 1 and 2.

And take the car for drive on highway, traffic with AC on and AC off again and check when the fans are kicking in.


Had a look at your STI's wiring diagram for the radiator fans. There's two control lines out of the ECM, manipulating three relays to run the two fans at either slow, or fast, speed; that's the same as mine.

The temperature observations in my linked thread were the result of observing the fan operation in real time in two instances. Again, what is puzzling, however, is why at some time the ECM is using one of the Mode tables, turning the fans on at their slower speed at around 201 F, and at other times using the other Mode table, where the coolant has to reach around 210 F before the fans come on in the slow mode.

Today I simulated coolant temperature by using a variable resistor in place of the coolant temperature sensor, and logged the ECM fan response as the temperature was varied from well below fan operation, through full operation. In this case, with the car parked, engine off, it was obvious that the ECM was using Mode A. The details are at this post: http://www.subaruoutback.org/forums/66- ... ost4477394

The fans almost never come on when the car is being driven (obviously, with the AC off) -- I don't recall seeing the Rad Fan gauges change from "0", so driving and observing might be somewhat futile. The earlier real time observations were both made while stopped, or moving very slowly (traffic "crawling") situations. One in March, when the outside temperature was just below freezing; the other in August with temperatures around 80 F. Interestingly, the fans were operating in Mode A in March -- fans coming on at the lower coolant temp -- and apparently in Mode B in August -- coolant allowed to go to the higher temp before fans came on.


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 Post subject: Re: Radiator fan "Modes" -- how to relate to fan operation?
PostPosted: Tue Dec 13, 2016 11:49 pm 
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I am sure its related to FAN number, in my car I can see that the FAN 1 is working then FAN 2 kicks in once it reaches a certain temperature defines in the FAN tables.
it is also proven by the FAN relay switch log. so each Fan has a table and its following that in my car.

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 Post subject: Re: Radiator fan "Modes" -- how to relate to fan operation?
PostPosted: Wed Dec 14, 2016 9:43 am 
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welaish wrote:
I am sure its related to FAN number, in my car I can see that the FAN 1 is working then FAN 2 kicks in once it reaches a certain temperature defines in the FAN tables.
it is also proven by the FAN relay switch log. so each Fan has a table and its following that in my car.


Interesting. The table you attached to your post on Dec. 11, entitled "B: Inspection" seems to be for the 2012 STI, at least according to the FSM I have, but that table makes no reference to one fan coming on, then the other. (It's just low speed or high speed.) And with the exception of the temperature ranges, it's very similar to the corresponding table for the fans in my 07 that I attached earlier.

Also, I believe the attached wiring diagram (below), is the correct one for the STI. If that is the case (and if not, please let me know!), then it verifies that both fans should be on at the same time, and not sequentially.

for my 07, Romraider displays two fan relay switches corresponding to the two relay control lines from the ECM in the wiring diagram. As I see it, when both switches are showing "0", the fans are off. When Fan relay #1 switch is at "1" but #2 is at "0", pin 11 of the ECM connector is grounded. This activates the sub fan relay. That connects power from MB-4 through the sub fan motor, but the circuit then continues through the main fan relay 2 to the main fan motor and then to ground. So the two motors are connected in series, in which case they both should run, but slower than "normal".

When Romraider shows both Fan relay switches at "1", all the relays are activated (both pins 11 and 12 of the ECM are grounded). This, in effect, connects each fan motor directly to a source of 12 V (i.e., they are no longer in series), and they both run at full speed.

There is a third "possibility". Fan relay 1 switch at "0" but fan relay 2 switch at "1". In this case, pin 12 of the ECM is grounded and both main fan relays would be activated but the sub fan relay would be off. The main fan would be powered through the main fan relay 1 while the sub fan would be cut off from power, so only the main fan would run, at full speed. However, why have only one fan running when the radiator is down-flow, and therefore a good half of the coolant flow through radiator would not be in the path of the air from the one fan? I have not seen this combination of relay switches on my 07.

I do appreciate this discussion and the possibility that I am misunderstanding the way the system works. If you could post a screen shot of the ROM rad fan tables (similar to what I have in the first post above) for the STI that might help clarify things.

That said, let me note that the fans in my 07 are working, and based on my earlier observations and the simulation test I did a couple of days ago, they do come on together at low, and high, speed at temperatures that correspond to the ROM tables. The question remains: Why, and based on what criteria, does the ECM use one or the other table, given that in one case the temperatures at which the fan(s) would be turned on is notably higher than the other?


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 Post subject: Re: Radiator fan "Modes" -- how to relate to fan operation?
PostPosted: Thu Dec 15, 2016 7:53 am 
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Mmm, that makes sense. Maybe I did not watch closely when the FANs were speeding and I though it's the other FAN kicks in. Let me re-check.

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