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Discussion Starter #1
Good day to everybody. Just got my RS warrior a last week ( second one) and having a bit of a problem so here goes.
I got the warrior as a non runner and was sitting . I tried working on it and realized that the bike was missing a Starting Circuit Relay module so I ordered one.
When that arrived, put it on and tried starting it and i would just crank and when I throttle up a bit it would have this big backfire ( like a cannon).
I noticed that when ever I connected the battery , the ECU get warm and if left long enough, will get HOT to touch especially on the thicker side ( the fat part ). Checked the fuses and connectors for short and I dont see any. I disconnected the battery when sitting.
Yesterday I had a breakthrough, I was able to fire it up when I checked the wiring to the ignition coil were backwards (front coil wire for the rear cylinder). I was able to make it run at first w/o the power commander and after installed the old power command unit with came installed with the bike.
Now I tested it yesterday, the ECU doesn't get HOT when its off ( before it gets hot even when off , just with the battery connected) but after riding around my neighborhood about 5 to 10 mins, the ECU is HOTTTT!
Question for the Gurus in the forum, What could be making the ECU hot? No fuses are blown, the aftermarket parts ( electrical wise) on the bike are power commander, a second horn on the middle of the bike, aftermarket tailights and rear turn signal ( which I presume are LEDs)
 

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Welcome to the Forum from Australia.
That’s a big lot of question there Rainman. I can guarantee that there will be more than enough help coming your way. Don’t forget to post a picture of your new ride.
 

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Maybe run the diagnostic feature and see what codes pop up.
 

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Is your warm idle set at 850~950 rpm to support battery charge and oil pump flow? Undervoltage creates heat in circuits, and reduced oil flow creates motor heat.

Also, if the bike's air:fuel is too lean it will run hot and that heat rises up from under the ECU.

Its maybe good to look at external culprits before assuming the ECU itself is failing.
 

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Discussion Starter #5
Ok just rode it around for about 6 mins and the ECU is hot, not from external but definitely internal.
Run the diagnostic mode and my decompressoon solenoid is not cycling.
Engine codes are 19 sidestand, 20 atmosphere value differences and 23 atmospheric sensor.
while I was doing the check, the ECU got super hot again
 

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So your motor and pipes are not generating the heat. And the battery is not physically hot. Correct?

Is the ECU too hot to touch, and is it "super hot" in just a localized area?

If you carefully look closely in the plug area there are little molded pin numbers. If the heat is nearer the pin side then disconnect both POS and NEG battery cables then very gently unplug the ECU to visually inspect pins for damage or corrosion. Gently take actions needed if any, and if it is not broken don't fix it lol. Then gently plug back in. Do not force it, pins will bend. Go slow and square. Its easy once you succeed once!

If no reason for the heat is found then meter battery voltage while running checking for undervoltage.

Let us know.
 

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Discussion Starter #7
Ok I just tried test the sidestand switch.
It function normally but I tried Alanh method to disconnect the blue wire and start the bike, kick stand up, pull clutch, put in gear. It dies. So I’m I looking for a shorted wire? i testEd sthe plug wire from the sidestand switch with a tester and switch is good.Is it related to the ECU getting hot?
Tested the voltahe on the battery. 13.89 when running though won’t go up to 14v when rev up. So definitely its not give the ECU a to much volts :confused:
 

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Discussion Starter #8
The ECU is hot on the body, the thick side (left side of youre looking at it where the part numbers area) battery is new, same response from old battery
 

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Ok I just tried test the sidestand switch.
It function normally but I tried Alanh method to disconnect the blue wire and start the bike, kick stand up, pull clutch, put in gear. It dies. So I’m I looking for a shorted wire? i testEd sthe plug wire from the sidestand switch with a tester and switch is good.Is it related to the ECU getting hot?
Tested the voltahe on the battery. 13.89 when running though won’t go up to 14v when rev up. So definitely its not give the ECU a to much volts :confused:
13.89 is plenty.

Bike running and kickstand-up and put in gear and it dies says the logic side of the start/injection relay has a problem or the relay itself has been compromised OR THE KICKSTAND SENSOR HAS BEEN COMPROMISED and the ECU gets a signal the kickstand is still down. Refer to the manual (or ah's material depending on where you are in the learning curve) and you will discover the next path! Cheer up you are hunting now!
 

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Discussion Starter #12
No luck, check the ECU connector ( no corrosion and sprayed contact cleaner ) inspected most of the wirings, unplug most of the connectors under the seat, unplug the pc3, No change still gets hot on he thick side ( not near the connector but the left side top) when turned on. Even when the bike is not running but the key just on ON position. 😔
 

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Okay then. Just to be certain, let's consider if the temperature is too hot. Its normal for ECU's to be hot. Inside there is even a heat sink to shed heat, and that is located on the thick side of course. Juice flows at key-on because the ECU is working.

On this bike you should be able to hold the ECU in your bare hand and not get burned. But it will feel hot. So the question is how hot.

If you hold a 110F item in your hand for awhile it will eventually turn your skin red and might even burn. If you touch a 150F item its likely to burn your skin quickly. By the time its 175F it will instantly burn skin.

Electronics run hot by nature. ECU's are built encased in order to be handled. If you measure the external temperature it could read as high as 150F if every circuit is active but its most likely going to read external temperature between 110F and 125F (which is cooler than early ECU's ran). There has never been a time when I could not hold the ECU on my warrior even in the garage in desert heat (out of direct sunlight).

Could you run some checks with this info and take a guess if maybe the ECU is operating within temperature limits? Use a meat thermometer or better yet a remote thermo unit. Maybe its okay.

Three other odd rare things to check.

From the battery NEG post the cable runs to a ground point on the frame near the motor oil filler cap. Gently remove that nut, clean away all corrosion including on the wire eye connectors, then gently replace and lightly torque. Post a clear uncluttered picture of the wires that are grounded there.

See the Service Manual for how to meter juice from the bike's voltage regulator. Its actually a Rectifier/Regulator. Because of what you have already posted this R/R is likely fine. But let's be certain its providing power within high/low limits. Note you will want to be certain the POS and NEG battery posts are clean and tight.

Do some reading about 12v parasitic drain. Things that draw voltage even at key-off. It might even be things added to the bike. Or a side effect of modifications. Under voltage creates higher amperage and that would create more heat until voltage rises.

Between me and you, I suspect the ECU is okay. But lets take these items off the table. After that, its usually necessary to send your ECU out to a special kind of test shop but not many are familiar with this one.

If there are no heat marks on the ECU case and if these added tests check okay, then odds are your ECU is okay at this time.
 

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Enclosing FYI only my 2004 under seat wiring that depicts the proper ECU placement above the battery tray. I have several modifications to the factory wiring such as a LEQ for my front & rear LED lighting, COD patch using a 12vdc relay and branched OEM snap connector wiring that is tapped into the main harness.

My .02 follows for troubleshooting only:
  • I would suggest you disconnect your fuel management system and connect as stock.
  • Remove the Headlight (15A) & Signal System (10A) Fuses to prevent battery discharge.
  • Trip the Engine Cut-Off Switch
  • Turn Key-On (you should hear NOTHING) and leave for 5-10 mins.
    • The ECU should be ambient temp
      • Key-OFF
Next Test Same as above but:
  • Reset Engine Cut-Off Switch to Run Position
  • Turn Key-On (you'll hear the F.I. Pump charge the fuel manifold, the Start Circuit Relay & F.I. Sys Relay will be audible and several seconds later you'll hear the F.I. Sys Relay drop-out and leave for 5-10 mins.
  • The ECU will be slightly warm on the tagged side (1st photo) in the ENGINE area of the tag.
Today I did a 100 mile trip in 90° F weather and the ECU was comfortable to hold in hand after arriving home. I would estimate that it was a uniform 105-110° F without any Hot Spots. IMHO 145° F is uncomfortable as an example only.

Installed accessories will not affect the ECU temp. Only the devices the ECU outputs too.
The ECU has a 5vdc isolated power supply that will create minimal amount of heat only.
I suspect that the Click-of-Death would generate additional spotted heat but this isn't the case for your scenario.



 

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Discussion Starter #15
Ok will try this weekend, been busy rebuilding another project ( triumph street triple) . I did try to remove the PC3 and the ECU still got warm/hot. From your pictures Alanh, the part that gets hot is the thick side( not where the wires plug in but the main body itself where its thicker compared to the other side ( left to right). anyways I did check the headlight bucket for wiring mods and it’s dead stock. Like I said in the previous post, the mods that I see is, taillight and back turn signals to LEDs and the fuel Management. I stand corrected on the second horn near the middle of the bike, looks stock.
As a quick fix. I actually bought a second ECU to try on, but still try Alanh’s suggestions 👍
 

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The guru's have given their advise, but I always like go back to basics.
Hot means short of some kind, and you mentioned the decompression solenoid is not working.
Did you unplug this and see if things get still hot (note you will get warnings)

Dutch
 

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Discussion Starter #17
I did unplug the decompression solenoid, and also all the wiring connectors under the seat, still got hot. I might be able to acquire a infrared thermometer soon to get some readings. I used a basic thermometer and it went up to 110 and the thermometer said too high.
 

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Discussion Starter #18
Ok, I done Alanh’s test and on the second test the ECU got
warm/ hotter. I got my second ECU and put it on without the PC3 and 5 mins of running, it’s fine. The idle wasn’t super, I have a vamce and home pro pipe and the coffin cover was out. Sound really lean. No I’m on the fence wheth to put back the PC3. I feel it works fine, the light go up and down, or should I just go back to a stock exhaust
 

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Rainman73 … It's unclear to me why you would replace the ECU?
I've never had the opportunity to open up the ECU but am quite confident that it is comprised of semiconductors and other solid state components that are totally encapsulated with a thermally conductive potting compound to dissipate heat from the components.
I would suggest you take your bike for a ride so that the ECU has a chance to normalize its temperature as I did in my OP.

I don't have a PCIII but would suspect that because it is powered from the Warrior 5vdc isolated power supply that this is the reason for the significant Delta-T (change in temperature) when you Key-On.
  • The PCIII USB is connected to the Injector & TPS harnesses in a daisy chain fashion and a single connection to the chassis ground.
 

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Discussion Starter #20
Given the choice, I would be hapl with the original ECU, I mean it works. The problem I feel will be that it will burn up while riding and leave me stranded with a 500lb plus bike. If it was an R/R heating up like that, I wouldn’t mind but the ECU... like I said if I had a infrared thermometer in hand I would have glady taken the readings since i know it’s way hotter than normal.
anyways I did connect the PC3 back and rode around for a least 5 mins around the neighborhood and the new ECU ( it actually looked tattier than my original one) was cool to touch. The way I always expected it to be. I’ll keep my original one as back up .
this will probably go to the unsolved mystery files in my book 👽
 
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