Fans won't turn on unless commanded through Evoscan --- converted 93VR4

[Keyan]

I did the wiring instructions on chromedecu.org to wire my fans to my chrome ecu. I verified that they are wired properly because if i use the command CE in evoscan, they turn on.

But, unless I command them on, they wont seem to want to turn on at all.

I altered the temperatures in my flash to have the high fans come on at 203f and go off at 190f.

Today while logging, my coolant temp got up to 220, (heatwave; its currently over 100 outside) and I couldn't hear the fans running. Commanded them on with CE and they temps dropped right down to 206 and would flucuate between 206 and 210.


Sooooo....... if the ECU has the ability to control the fans as proven by commanding them on, then why wont they turn on when they should? :confused:

[Toni]

Did you remove the "Radiator Fan Motor Control Relay?" Not sure if not removing that will cause your issues but Brett's directions recommends doing so. Haven't read into why or what it really does etc. Also, have you tried changing the turn on temps for something much lower just to see?

[mb3000]

I don't know about the chrome ecu all that much, but there might be some vehicle speed requirements that might be affecting your situation.

[Greg E]

Vehicle speed, AC switch and ECT switch the fans on in the code.

[Keyan]

i will have to take a deeper look at it when i get the time.

[Greg E]

Are you running a Jesters PnP or a clone from Brett?

[striker2]

Keyan, did you ever figure this out? Im having a similar problem, also on a 93. I can activate the fans via evoscan no problem but just sitting at idle the temps got up to over 200 and the high speed fans never turned on (I set the high to come on at 200 and off at 190). the low speed fan works fine though.

[striker2]

did an experiment this morning. changed the tune to have the high speed fans come on at 100F. before starting the car I used evoscan to check what the coolant and intake temps were (should be the same since it sat overnight). coolant showed 73F and intake showed 70F so i figured that was close enough. started the car and as it was warming up the high speed fans did kick on, but not until evoscan showed the temp was at 105F. So im not sure if that means that evoscans scaling is off or if the PCM has a small delay between reaching the temp and actually turning on the fans. I have noticed that Evoscan typically reports about 10F higher than my gauge when warmed up.

[Greg E]

I'm starting to wonder if the 1G coolant temp sensor is scaled differently. That would explain the difference. The connector for it is different so it would make sense.

Where is your aftermarket coolant gauge sensor mounted? In the thermostat housing next to the stock sensor?

[striker2]

yup, mounted in the thermostat housing. if its scaled differently that would explain the fan issues as well as the difference in temp from evoscan.

[Greg E]

If you got time, I am wondering if I could talk you into taking a few readings for me an comparing them to your real coolant temp gauge.

It'd be a simple matter of rescaling the coolant temperature sensor table to match.

...or you could just swap in a 2G coolant temp sensor...

[striker2]

I could probably take some readings Thursday morning since I dont go into work till 3PM that day. I might be able to get some tomorrow morning though. what readings are you wanting? I have a nice DMM as well as an infrared thermometer and the aftermarket coolant temp gauge.

[Greg E]

I need you to get some data point for me. Just tell me what EVOScan says when the coolant temp is actually 60degF, then again at 90, then again at 120, 150, 180.... Precision is key. If you use your thermo coupler, make sure it's setup in the thermostat housing as close to the stock sensor as possible.

I can come up with a revised scaling from there.

Those infrared thermometers are nice but won't work for our purposes. :(

[Keyan]

i havent gotten this figured out yet. havent had time.

with the car at operating temp with an oem thermostat, evoscan reads 179deg.

that's all i know. lol

[striker2]

ok, the coolant was at 83F after sitting over night so thats as low as I could get.

EvoScan...DMM
85............83
91............90
103..........100
111..........110
122..........120
125..........130 (not sure why but evoscan bounced up and down a bit between 120 and 130 on the DMM, it went up to 132 at 131)
140..........140
149..........150
162..........160
170..........170
180..........180
192..........190

the low speed passenger fan kicked in at 193/193 and it dropped it down and kind of stabilized at ~185. its set to come on at 190 and off at 181 (will be changing that to off at 185 though). so it appears that the scaling is probably right (or at least close enough, seemed to be off slightly at cooler temps), my gauge reads about 10-15* low, and the fans dont come on right at the set temp but after some delay (probably a timer in the code somewhere would be my guess).

[dferguson]

hey Greg just saw this post and was reading though it,i have a 91 and noticed that my lcdbc was about 9 degrees higher than my after market temp gauge,
just thought it was my aftermarket temp gauge was maybe wrong.havent looked at in evoscan yet,maybe there is something to what your thinking on 1st gen vs. 2nd gen on the scaling.just thought I would throw that out there had noticed it for a while now.

[striker2]

A few weeks ago I was doing some work and pulled the battery (of course resetting the ECU in the process). I noticed some time after that my high speed fan was working properly. Two days ago I flashed a change to the ECU (and have been doing some more tuning since) and now it seems that the high speed fan isnt coming on again. I will be doing some more tuning so im not going to reset the ECU just yet but after Im done I will disconnect the battery and see if the fan works again after that.

[Greg E]

I highly doubt a flash change caused your fan to intermittently work. Unless you forgot to copy the table over there's no internal reason to the ECU why that wouldn't be working.

[striker2]

I cant see why it would either but since the high speed fan started working properly after disconnecting the battery last time its a simple and free test that wont hurt anything.