ECU replaced and now voltage regulator playing up?

Stevea4117

Stevea4117

Joined
Jul 12, 2022
Messages
17
Age
54
Location
Kent
Bike
ST1300
Guys,
My ecu on 04 st1300 has died I have researched replacement options. Does anyone have any knowledge or experience on this subject? If ecu is replaced will I have to replace key ,ignition barrell, etc.
 
You'd need at least an ECU and the ignition barrel and key matched to that ECU. I would assume that you could then remove the transponder chip from the key and transplant it in your own key, thus making it unnecessary to swap out the ignition barrel and all the other locks. The HISS ring just confirms to the ECU that the transponder chip is the correct one. If I am wrong I'm sure someone will chime in!

If it's definitely the ECU, watch out that you get one with the same part number as there were changes over the years.
 
This happend on the return leg of a 1600mile trip. Stopped at a service station filled up and had a quick cuppa. Whilst doing so I could hear a bizzare high pitched tone whilst bike was switched off. One hour later on motorway 85mph bike cut out no electrics rev counter, speedo, lights, indicators the lot went, couldn't bump it whilst rolling. Pulled in absolutely nothing no power. However did hear fuel pump priming. On checking battery noted a large bulge. Recovered to a garage in France, they just constantly kept blowing fuse. They cut black wire between two relays. Fuse didn't blow but bike would not fire.
Waited 53 days for bike to be repatriated and now at auto electrical specialist who tells me that it's the ecu that's dead.

Thanks for that very helpful.

Hound said:
You'd need at least an ECU and the ignition barrel and key matched to that ECU. I would assume that you could then remove the transponder chip from the key and transplant it in your own key, thus making it unnecessary to swap out the ignition barrel and all the other locks. The HISS ring just confirms to the ECU that the transponder chip is the correct one. If I am wrong I'm sure someone will chime in!

If it's definitely the ECU, watch out that you get one with the same part number as there were changes over the years.
Click to expand...
 
Stevea4117 said:
This happend on the return leg of a 1600mile trip. Stopped at a service station filled up and had a quick cuppa. Whilst doing so I could hear a bizzare high pitched tone whilst bike was switched off. One hour later on motorway 85mph bike cut out no electrics rev counter, speedo, lights, indicators the lot went, couldn't bump it whilst rolling. Pulled in absolutely nothing no power. However did hear fuel pump priming. On checking battery noted a large bulge. Recovered to a garage in France, they just constantly kept blowing fuse. They cut black wire between two relays. Fuse didn't blow but bike would not fire.
Waited 53 days for bike to be repatriated and now at auto electrical specialist who tells me that it's the ecu that's dead.

Thanks for that very helpful.
Click to expand...
"However did hear fuel pump priming."The ECM turns on the fuel pump. ECM dead ??
 
Some idiot cut wires?
Just because you hear the fuel pump pressurizing, does not mean it’s holding that pressure.
You may have a damaged fuel line bleeding off pressure.
 
Now the ecu has been replaced would appear that voltage regulator is playing up. At 1000 rpm voltage reads 14.8v when reved up to 2500 rpm voltage rises to 18.3v. Do you know if I can replace the regulator as a new alternator costs £1200 + vat.
 
That doesn't make sense. The generator doesn't fluctuate like that. It's either on or off.
Consult your manual.
 
aniwack said:
That doesn't make sense. The generator doesn't fluctuate like that. It's either on or off.
Consult your manual.
Click to expand...

Stevea4117 said:
My understanding was that the regulator maintains the voltage return to battery of 14.5v
Click to expand...
RR uses linear regulator shunt circuit. Similar to old-style selenium diode regulators with diode replaced by power transistor in regulator stage.

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It splits input voltage into 2 output legs (5) and (4) using voltage-divider ladder. One leg (5) gets 14.5v and any excess is dumped to ground (4).

So at idle with just 18 VAC coming out of alternator:
(5) -> 14.5v
(4) -> dumps 3.5v to ground

At higher RPMs and alternator outputs 40 VAC
(5) -> 14.5v
(4) -> dumps 25.5v to ground
 
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Chris09 said:
doesn't the fuel pump run until a pressure switch makes?
Click to expand...
Only on carby bikes with reciprocating pumps (like bicycle air pump). ST1300 uses rotary pump that runs fulltime when powered by pump relay. Which is activated by ECU.

Internal FPR on pump-assembly builds required pressure to send to fuel-rails. Excess flow-volume is dumped back into tank to prevent stalling pump.
 
Stevea4117 said:
This happend on the return leg of a 1600mile trip. Stopped at a service station filled up and had a quick cuppa. Whilst doing so I could hear a bizzare high pitched tone whilst bike was switched off. One hour later on motorway 85mph bike cut out no electrics rev counter, speedo, lights, indicators the lot went, couldn't bump it whilst rolling. Pulled in absolutely nothing no power. However did hear fuel pump priming. On checking battery noted a large bulge. Recovered to a garage in France, they just constantly kept blowing fuse. They cut black wire between two relays. Fuse didn't blow but bike would not fire.
Waited 53 days for bike to be repatriated and now at auto electrical specialist who tells me that it's the ecu that's dead.

Thanks for that very helpful.
Click to expand...
Those EEEEDIOTS!!!! Every single one of them!!

1. hissing/whining noise is gas escaping from overcharged battery. Venting wasn’t sufficiently fast enough and gas built up enough to balloon battery casing.

2. blk wire is activation power from start/stop switch that turns ON BAS-relay (main power relay) that powers everything on bike. Cutting that wire pretty much disables everything on bike.

Regulator most likely problem part all along. It’s what fried your battery initially. Measuring at this point would’ve identified dead battery as why your bike died. And further measurement would’ve shown RR is what killed battery. Damn Frogs screwed up your wiring and probably blew your ECU.
 
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