I know this has been discussed over and over. I know in 165 ECM, only Fan 1 is controlled via the computer. Fan 2 is controlled via a thermo switch on the head which is hard coded to a given temperature.
I am burning chips myself and converted from 32B to 6E. The NO / NC flag is fine as the fan is not off or on all the time.
I have a 180 thermostat and I lowered the Fan 1 On (For both A/C on and A/C off) to 200. Fan 1 Off (again for both A/C on and A/C off) is set to 190.

This issue I have is that Fan 1 comes on at around 180 no matter what setting I put. It also remains on even if the temperature gets down to 176.
I was suspecting that someone hacked the wiring so I connected an ALDL cable to see the Fan Request flag and also monitor the coolant temperature from the ECMs sensor (the dash and ecm sensors are different). From the ALDL stream I can see the Fan Request flag going in 'Requested' state at around 180 and never goes back to 'Not requested'. This confirms what I was seeing from the dash.

I couldnt find anyone having a similar issue. Any help on this strange behavior? Not that it really matters but I am using the 6e_expanded xdf file. The normal 6e xdf still displays the same temperature values in my bin.

Note that for the sake of clarity, I currently do not have gas in the AC lines. AC pressure switch is connected. Dont think it is relevant but wanted to lay out all the details.

 

You just seem to have all kind of issues with this system lol

fans are pretty simple. Sounds like you have things set correctly except for the ARAP cooling fan N/O. That should be set for fbodys

regardless, if ecm data is reading 180, then fan should not be turning on. For some reason its like the ecm is thinking 180 is actually 200. But not sure how that could even be possible

 

Indeed I am always on the chase of a problem on here. The N/O switch is set. Its the first thing i did when i switched to 6e.

Cant understand how the ECM is interpreting 180 as 200!!

 

If you move the temp setting in the chip up or down, does fan respond accordingly?

 

After some late night investigation online, it seems that the Primary Fan is controlled in 3 possible ways:
1. From the PROM with the setting that I am referring to
2. From the AC Pressure switch
3. From the thermo switch on the passenger side head.

What I didnt know is that 2 and 3 work by sending a fan request signal to the ECM and it is always the ECM which energizes the FAN 1 Relay (to GND). This means that even if the temp didnt hit the configured value in the PROM, if any one of 2 or 3 are true, I would still see the 'Fan requested' signal in the ALDL stream. I was mistakenly assuming that 2 and 3 take over the ECM to power up FAN 1.

So now my next step will be to disconnect 2 and 3 and see if I get FAN 1 to switch on at 200 and off at 190. If this is the case, it probably means that the pass side head switch has been replaced by a 180 On switch or else the AC pressure switch is acting up.

Again, will keep my findings updated on this thread to help others which might encounter the same issue.

 

Looking at the wiring diagrams, I believe the main cooling fan is triggered only by ecm and the a/c pressure switch. The “heavy duty cooling fan” is tied into the head switch and a/c pressure switch.

either way, removing the a/c switch and head switch temporarily should let you know what is up

 

You can see below from an 1988 Service manual that both the pressure and the temp switch feed into D11 which is a FAN request signal for the ECM to ground C1 and switch on the Primary fan. The Temperature sensor (under the thermostat) feeds into C10.

 

http://austinthirdgen.org/mkportal/m...ine_wiring.gif

thats not how im understanding the schematic

D11 is just said to be the pressure signal from a/c

regardless, try it all ways to be sure

 

For sure the two diagrams dont match in logic. And what is the E connector in a 165 ECM? AFAIK there are only A, B, C and D connectors labels...
Anyway I will try to short the pass head switch to ground and the AC switch one by one and see what happens just to clarify this logic. Will also monitor ALDL stream for the fan request flag while these are shorted.
Thanks for your help. Really appreciate your willingness to help mate.

 

Some Updates which might be interesting for others. This is what I discovered:
1. Shorted ALDL pin A <> B. This should power on ALL ECM controlled relays excluding the Injector drivers..... No FANs came on
2. Troubleshoot this issue... Blown Fuse. (Long story short, PO had for some reason removed the fusible links for the Fan relays replacing them with a Fuse. I separated the supply into two separate fuses (20A each) directly from the battery for the Fan relays as I was getting this fuse blown intermittently and wanted to see which FAN is causing this and also split the risk). Before I delve into seeing why fuse is blowing intermittently, can someone let me know from where and what type of fusible links I need for the FANs?
3. Once the fuse was replaced, ALDL A <> B causes Primary Fan to power on.
4. Connected laptop to ALDL monitoring the Fan request. Shorting AC Pressure switch, AUX Fan kicks in and FAN request is toggled.
5. Shorting Pass side head switch to Ground, AUX Fan kicks in and FAN request is toggled.
6. Tracing wires (using multimeter), I can conclude that the Pass Head switch and AC Press Switch are logical OR.

Conclusion.
- The diagram that I pasted is for sure the correct one.
- When AC Pressure OR the Pass side switch activate, the ECU is alerted about this via D11 pin.
- Either the PO changed the Pass side switch from 230F to 180F or the switch itself is faulty.
- Most probably even if the fuse wasnt blown, with my current PROM setting (200 Activate), the Primary Fan will never come on as the thanks to the Pass Head switch, the temperature is always swinging between 176 and 186. This might not be the case in summer.
- I am also assuming that the ECM uses the Fan Requested signal from the AC press / Pass head to know that the A/C is on and this allowing for different Fan On settings with A/C on or off. I couldnt find any wires going from the A/C switch in the dash to the ECM so this must be it.

Way forward.
- Will try to see if I manage to read some stamping on the Pass side switch. If I were to change it, do I need to drain coolant?
- Sort out the blown fuse issue. Can someone provide me a link from where to get fusible links and the size required? Couldn't find anyone who knows what they are locally!!
- Will keep the Pass side switch disconnected for the time being to see how the FAN behaves at 200 via the ECM.

 

correct but neither of those activate the primary fan right? D11 does not trigger C1

glad you found the issue with the fuse. Nothing wrong with a 186/176 setting. If you want it to run hotter i suppose you could throw in a different switch

 

Correct. On that I was wrong . D11 does not trigger C1. Its just used to inform the ECM that AC is on. Flag name is a bit misleading (FAN REQUESTED)

Nothing wrong true but in this way the AUX fan will never switch off as the engine will never go down to 176 especially on TransAM without front bumper vents. We have to rely solely on the effectiveness of the Air Dam. Dont think the FAN will like it either.

 

The D11 input is to tell the ECM to turn on the primary fan. That wire/signal also grounds the secondary fan relay coil to enable it.

A/C compressor clutch active input is on pin B8.

RBob.

 

I also thought that D11 is used to tell the ECM to switch on also the primary fan but I tried it (after I fixed the fuse) and I only got the AUX fan running when I shorted the AC pressure switch albeit I could see the 'FAN Request' in ALDL stream.

 

So I disconnected the Pass head thermostatic switch and as expected, FAN is now coming on according to the temperature set in the PROM. I can say this is way better as even if the engine is at 200, before the car starts, the fan isnt powered on thus it doesnt drain the battery if you are on Ign On Engine Off. Also temperature seems to be a lot better handled in these regions.
Will definitely replace the Pass Head switch to a 220 or 230 one.

What was puzzling is the fact that the ALDL 'Fan Request' flag DOESNT get set (Requested) when the ECM commands the Primary fan on. This is set only if AC Pressure is high or of the Pass Switch is shorted to ground.

I guess this concludes my fan investigations

 

Was the engine running? If not the ECM won't enable the primary fan.

RBob.

 

You are right Rbob. Engine wasn’t running. Infact as I said if the engine is not running even if the temp is more than the fan on temp, primary wont start until the engine is running.

 

Good thread. I remember this from the Firebird I had, which was in all aspects an '89 GTA clone. I had a manual overide switch for the secondary fan, and found out immediately that it would trigger the primary to go on as well. After diving into the schematics, I learned the same conclusion in a different way. Yes, you can change the fan switch without draining the coolant, if it's on a cold motor, you work fast, and don't mind a small puddle. :-)