Yamaha f90 iac getting hot

[Mike781matco]

I have an 05 f90 tlrd. With the battery switch on and I cycle the ignition key on then back off, the iac will start to heat up to 134degrees f. I measured with a thermo gun. Takes about 20 mins to get to that temp With the key still off. Won’t cool down until I turn the battery off. Has around 250 hours runs and idles great. Only noticed it when I had the cowling off and leaned my arm against it. Normal? I did some testing. I checked voltage to the ecm. Battery off key off 0 volts. Battery on key off 0 volts. Battery on key on 12.7 volts. Battery on key off 12.7 ( after being on for 5 mins) iac starting to warm up. I don’t get 0 volts again until I turn the battery back off. Then I can turn the battery back on and get 0 until the key is cycled. Can the relay “stick” until power is killed completely and then revert back to normal until I repeat that cycling process? I ordered a new relay should be here in a few days. Any other ideas? Thanks

[boscoe99]

Certainly a relay can fail closed.

Have you tested the relay with a multimeter to see if the relay is closed with no power being applied to the control circuit?

Have you disconnected the main relay connector to see if the IAC valve does not get hot with the battery on and the key off?

[boscoe99]

No one is in a better position to trouble shoot your problem than you are.

[Mike781matco]

Disconnected from power the relay tests normal with a meter. With the battery on, the iac does not get warm and ecu does not get voltage until o cycle the key on and off. Then the iac will start to warm up and ecu will have 12.7 to it from the relay until the battery is turned off. I can then immediately turn the battery back on with No ecu voltage or iac temp until the key is cycled again.

[Mike781matco]

It’s like it’s sticking closed until power is completely disconnected

[boscoe99]

With the battery on and after turning the key off, measure the green wire to the tachometer and see if you have voltage there.

[Mike781matco]

Just went out and tested it. Batt off key off 0 volts. Batt on key off 0 volts. batt on key on 12.5. Batt on key cycled back off 12.3. Turn batt off then back on 0 volts

[boscoe99]

Where are you measuring your voltage?

[Mike781matco]

Green wire at main harness connector? Hope that’s it. I can re test if I was at the wrong spot

[99yam40]

I thought the ecu ran the IAC to 100% when turning the key off.
do you hear it rattling when this happens?
maybe the IAC is not moving,
but I would not think it would try running it for that long at key off because it just sends a signal to go to 100%, it does not get any feedback to let it know if it moved or not

[Mike781matco]

I don’t hear it moving when I cycle the key, but It connected it to yds and it moved when I preformed the test

[Mike781matco]

Also, it Idled fine on the hose yesterday

[ausnoelm]

If you don't hear it "rattle" when turned off, do not continue to operate the motor, or buy a new ECU now!

[Mike781matco]

I went out this morning checked voltage on the green wire going to the tach from key switch. Batt on (key not yet cycled on and off) I got 0 volts. I did have 12.8 at the red wire. Cycled the key on and back off and the green wire to the tach had 11.9-12. Disconnected key switch completely and still had same voltage at the plug. Turned batt off and back on got 0 on tach… does the ecu control the main relay or does the main relay control the ecu?

[boscoe99]

Both I believe.

My computer is down. More to follow when it is up and running.