Electrical gremlins. Two ideas you can try.
- COOLING FAN CIRCUIT - all your problems could be with that darn fan.
Do you have a former air conditioned car? Assuming you do not, put a voltmeter on the
fan relay’s coil ground, and then let the car run through a fan cycle. Fan actuation
with a bad relay diode can send tremendous voltage into the Emerald - 200V or more.
Instructions:
Use Wiring Diagram in Service Notes manual page Exige-29 as a guide.
Detach the front relay block. From the back of the fan relay mount, disconnect the blue
wire with grey stripe, (can also be a blue wire with grey tape at the end), jam the
positive voltmeter contact into the relay mount where the blue-grey wire once was, connect the negative side of the volt meter to the blue-grey wire. Better yet, connect the negative side of the voltmeter to pin 57 of the ECU.
If you do have an A/C car, you can do the same test, but the blue-grey wire is located
elsewhere, see page PH-24 in the Service Notes manual.
If you are allergic to voltmeters and relays, the alternative to swap the Fan relay for
a fresh, Chinese-made Tyco (perhaps you prefer Bosch) 30 AMP SPST relay. They cost less than the beer you should be drinking by now.
If your Emerald is too messed up to run this test, then run it with the original Lotus
ECU. I assume you don’t care that you fry it.
- CHECKING HI-VOLTAGE RELAYS
Is the wiring in your car altered in any way? Your car could be setup like Sheet 1 in
the Service Notes (Exige-27), or do you have the “undocumented” relay between Splice NN
and Splice H (see Exige-27 to see the splices)? Test the relays, or better yet, just
throw the relays away and put some freshies in. Relays are so cheap why worry.
INSTRUCTIONS
Pull the relay centre off of the back bulkhead, snap-off the black plastic cover on the
backside, and check the wires - I had some wire insulation melted at the crank relay
and the ignition relay - yours may have an intermittent short, especially if it gets
wet back there.
If you do not have the “undocumented” relay between Splices NN and H, "unintentional
activity" between the ignition and crank relays could affect your ECU.
For a great reference for testing relays, download “UNDERSTANDING RELAYS” from the www.autoshop101.com site.
I am sure all my colloquial language translates perfectly to German!