Fans run constantly Ls3 with Psi harness and ecu.......

[cpd004]

I really appreciate all the help. At this point, after talking to PSI, I will probably return the ecm to them and try and work with what came with my engine and a local tuner.

I was under the impression that with the fans controlled by relays, the ecm could only turn them on or off. Not vary their speeds as what I would expect the pwm setting to mean. Am I wrong here?

I've read a bunch of stuff since having these issues and the information out there is overwhelming. Oddly, some of it conflicts but the outcome has been right for different people. I found one post that said if anything is put in the 192 bucket, his fans run all the time.

[1989GTA]

"I was under the impression that with the fans controlled by relays, the ecm could only turn them on or off. Not vary their speeds as what I would expect the pwm setting to mean. Am I wrong here?"

That is correct. They only turn them on and off in the discrete mode. No percentages involved. However buried in the "software" of the ECM it appears that the number 50 will turn on fan #1 and the number 90 will turn on fan #2. It also appears that the number 50 will turn off fan number 2 and the number 25 will turn off fan number 1.

In your chart of the engine coolant temperature your lowest number is 40 so the fan will never turn off. It needs at least a 25. Also it is in the 192 slot which I have also read that causes problems. IMHO it is the numbers in the engine coolant temp chart that are the problem. The others look OK.

[terrydmorgan]

I'm certainly no expert on this issue. And no offense to anyone, but based on my understanding, I think there's some confusion here. If I read your comments correctly, you're running two fans from a single relay. If that's right, then you can't control the fans separately. They'll turn off/on together and they'll be on full speed or off. pwm allows you to vary the speed of the fans, but you're not set up to run PWM (you need a separate controller). Now, turning to the charts that show different percentages, they are referring to percentage of full fan speed. For example, the chart/graph in post #12 indicates that if PWM were enabled, the fan would turn on when the temperature reached 217 degrees and the fan would run at 43% of its maximum speed. Thereafter, as the temperature continued to increase so would the speed of the fan. At 221 degrees, the fan speed would be increased to 48%. Likewise, at 232 degrees, fan speed would increase to 90% of the maximum speed.
Now, turning to your problem, it sounds like PWM is enabled. You need to make sure of a couple things: 1) discrete mode must be turned on and PWM must be turned off; and 2) make sure you've got the correct wire from the ECM connected to your relay (the PWM signal and the discrete signal may be on two different wires and you may have the wrong one connected to the relay). I would imagine that PSI could readily answer these questions for you. PSI should be able to program your ECM for discrete mode and to set the temperature you want to cause the fans to turn on full speed.
There is one other possibility. The ECM can also turn on the radiator fans in response to the AC being turned on. Do you have a pressure sensor connected to the AC and feeding an electrical signal to the ECM? If so, it could be turning the fans on too.
Finally, if you're interested in running PWM so that your fans will run at slower speeds and be quieter, then check out my posts from a couple of months ago. I've laid out the parts you need and the electrical connections you'll need to make.
Hope this helps and doesn't just confuse the issue.

[cpd004]

Each fan has it's own relay. There is no provision anywhere in the harness for an AC pressure switch. The signal wires for the fans from the ecm are wired as shown in the PSI instruction sheet. Also, it looks to me like 'Discrete' is the setting the fans are on based on the 'Fan Type' slot.

pwm fans definitely seems like the way to go, but at this point, I'd like to get what I have working properly. I'll try getting the numbers in the 'Fan Desired' portion changed and see what happens.

Again...thanks for the help!!

[cpd004]

I got my original E38 ECM back from Speed Inc. and no fans! All seems to be ok now. I took the car for a very short ride only around a few side streets, and it seems ok. I'm sure it would benefit for a dyno tune, but I won't know till I get some more time behind the wheel. I didn't want to go too far as I was riding around with open headers....very loud!

On a side note, I am running a TCM from a Trailblazer that wasn't touched by Speed Inc. It is controlling a 4L60e built by RPM transmissions. I just picked it up from a local parts yard as I have to send back the PSI ECM/TCM. It did ok on the ride as far as I can tell and only got to 2nd gear since I was going so slowly. Am I causing any damage using the TCM?



MODS, feel free to move this thread as it is no longer an emergency...just trying to keep the posts together for consistency.

[1989GTA]

That is good news. Any idea what the new fan tables look like?

[cpd004]

I didn't ask Speed Inc. I'm not sure that they'd send me a screenshot.

[1989GTA]

That's fine as long they are working correctly that is the main thing.

[cpd004]

Here we go again. Now the relays just buzz. Luckily that's explained in the link above (thanks ChevelleNV). Unfortunately I'll have to send the ECM back to Speed Inc. I'm so sick of this back and forth stuff with this ECM.

I thought the problem was solved but didn't wait long enough for the ECM to kick the fans on when testing it.

[1989GTA]

Sounds like they left it in the pwm mode and should have put it in the discreet mode for your relays.

[rick90gta]

what type of relays are you running? if you are using pwm fans, you need a solid state relay as a standard relay can't cycle fast enough to control them

[cpd004]

The issue has been corrected by Speed Inc. They cycle on and off now correctly.