Area Representative Richard Price Posted July 6, 2017 Area Representative Share Posted July 6, 2017 I've just assisted my son Tom swapping his EU3 MEMS for an MBE ECU on his ex MegaGrad ex race car. We've cut up a scrap EU3 ECU that I've then used the connector to make an adaptor between the existing wiring loom to the MBE ECU. The engine part works perfectly. Unfortunately, the standard alternator is not charging. I've proved the alternator by fitting it to my own EU3. I guess the alternator is not being excited. It does not look to have had a functioning "ignition" lamp for some time, but the cars Stack dash has displayed healthy charging voltage (but now simply shows battery voltage when running), so that does not look to be the cause. The other connection from the alternator goes to pin 35 of the ECU, which the Caterham wiring diagrams label "alternator sensor".Does anyone know the characteristic of Pin 35? Could the be the cause of our charging issue?Alternatively, what needs to be connected to the two auxiliary connections (Brown/yellow going to the "ignition indicator" and white/red that goes to the ECU) of the alternator to make it charge? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 6, 2017 Member Share Posted July 6, 2017 What sort of alternator and how many terminals?Is the warning light incandescant or LED? Does it illuminate if you disconnect everything and rig a temporary feed and earth?Jonathan Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted July 6, 2017 Author Area Representative Share Posted July 6, 2017 Jonathan,Its that standard EU3 Bosch alternator.It has the one large connection that loops across to the starter motor, then an elongated D shaped connector with two connections. A brown/yellow that goes to the "ignition" indicator lamp (which has not functioned for the three years that he's had the car), and a white/red that used to go to pin 35 of the EU3 ECU. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 6, 2017 Member Share Posted July 6, 2017 I don't know what pin 35 does and would test and fix the warning light and its circuit and then see if the alternator wakes up.Jonathan Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted July 6, 2017 Author Area Representative Share Posted July 6, 2017 would test and fix the warning light and its circuit and then see if the alternator wakes up.I should have said. I've already done that, and it still does not charge. Link to comment Share on other sites More sharing options...
simon_h Posted July 6, 2017 Share Posted July 6, 2017 Pin 35 is a load feedback for the std ecu. It can be disconnected and the alternator will still work ok. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 7, 2017 Member Share Posted July 7, 2017 Are these right: The alternator works in another car but not this one Pin 35 isn't relevant The exciting current for that alternator comes through the warning light circuit The warning light isn't working?Jonathan Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted July 7, 2017 Author Area Representative Share Posted July 7, 2017 Jonathan,Yes. All of those statements were correct....I have no idea how it was charging before the engine swap. It last ran late last year...It now has a functioning "ignition" light which does indeed provide initial excitation. (however, if there is anything connected to the white/red then it won't charge irrespective of what is connected to the brown/yellow ignition light connection) We'd been fooled into thinking the alternator stopped charging whilst mapping (fueled by our concerns over noisy alternator bearings before mapping, but no time to fix it before our scheduled dyno session) . On reflection, it was not charging at any point, and, part way through mapping, the battery voltage dropped below an acceptable limit. Mapping was completed hooked up to a battery charger. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 9, 2017 Member Share Posted July 9, 2017 With the white/red wire disconnected at the alternator what does the warning light show and what's the voltage across the battery: With ignition on but the engine not running Minimum voltage during cranking (ignore the warning light) At 3,000 rpm?Jonathan Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now