hmm, there seem to be some problem when changed P28 (which I dont have anymore) to Hondata - AC wont go on anymore and both radiators fans go on when ignition is turned on. Before they both acted normal.

We have checkd fuses, relays (not yet AC relay) and sensors - nothing.

I know theres some option in Hondata where you can determine AC & fans switch off RPMs but thats not the problem here...

Does anybody know is there some other fan/ac options in Hondata - so is this calibration problem or is there some wiring to be done or something?

 

Might be a better question for the engine management section, but...

What ecu is the Hondata installed on, although it shouldn't make a difference?

What car is it installed in? I assume a Prelude that is OBDI.

Did anything else change, or only the ecu?

Sounds to me like a wiring issue, or the Hondata is set up to use an A/C switch for something else, like a nitrous or boost output.

 

Originally OBD2A (fifth gen) but now its converted to OBD1
We made some engine rebuilding (once again) - previously everything have worked ok exept now with Hondata

 

Ok, I would check at the ecu on connectors A12 and A15, those are the fan control and AC clutch, respectively. OBD1 pinouts are on Hondata site as well.

 

I would check the hondata map. check all auxiliary functions and make sure nothing is running off the fan switch. also check the fan override setting, make sure it's set to a reasonable temperature of around 185*F or so, nothing lower.

 

Ok thank you. Some more checking.... Havent made pin modifications to conversion harness, shouldnt it just... work?
I tried that with my previous OBD1 conversion harness and with that too fans were on.

AC seem to be working but those fans live their own life

Fans didnt react to Hondata sensor out put test (bacause they are on), AC did.

can you tip in what section I can see that? Only thing the tuner changed was to wideband to EGR, but I havent checkd others are they normal

 

Ah conversion harness...

I would check all of the leads on that, see if possibly one has had a wire or solder wear through the sleeving, and may be touching another wire, grounding out on something etc. I had that happen to me, a chunk of solder wore through the heat shrink and was grounding out my MAP sensor intermittently. As soon as I removed that harness, the issue was gone. It had been fine for 5-6 years before that, so it was a hard issue to find. I had to pretty much run the car and jiggle and test wires, after realizing that I had checked everything good, and then it started acting up as soon as I pushed the carpet up in the footwell.

But with what motoxxxman said, you have to check each table, all of the nitrous tables, boost tables, etc and ensure that they are turned off if not in use, and check what input or output they have selected. If one is A12, it needs to be changed in the map.

One other thought, what coolant temp does the ecu see as soon as the key is on? If one of the coolant sensors is bad and reading high, it could just be kicking the fan on right away. Not sure if your car has 2 or 3 sensors, but it could be causing the fans to run, while not showing as over temp on the gauge.

And last thought, and relays in the system should be triple checked, in case one is stuck on and energized all the time, even without a signal.

 

That was my first move - another harness but fan issue stayed with both of them

There has been temp reading ok in hondata as well as gauge works normally.
Those 2 sends signal to 3rd sensor - fan switch and we have tried with another fan switch as well - no change in fan behavior

 

Even when we unplugged ecu - fans are on if they get power ignition turned on so ecu signals doesnt really matter?

 

*solved*

fix was 2 mixed (ac/radiator) connectors... :D

 

Haha, glad you found it!