Hi guys, I have a 1980 series 1 with an injected 12a and microtech ecu. I went to fire it up the other day and noticed the generator warning light was on, the tacho was sitting at about 200rpm regardless of the actual engine rpm, and the idle was rougher than usual... the car ran considerably worse when I manually turned the fans on.

Alternator output is 14v, and around 40 amps. .2V drop to the positive terminal of the battery (in the boot). I bypassed the ignition switch altogether but that didn't change anything either. The battery terminals appear to be tight... any suggestions? The car wiring has been extensively messed with, which won't help matters... Thanks in advance

 

You sure the battery is good? Sounds like it may not be taking or getting a charge.

 

Battery is old and not great, but I (incorrectly?) Thought that it wouldn't be the issue as long as the alternator was doing its job?

 

Start with the most basic step. 1.) Be sure that your main ground-to-chassis is a good solid ground. These cars are old, and the main ground wire will corrode over time; of which may not be visible. I've changed my battery ground-to-chassis at least twice over the years; and it makes a significant difference.

My RX is not my daily driver, and stays often in its stable for weeks at a time; and I'm planning on replacing my main ground wire before summertime on mine.

I've also seen Amazon and Ebay sales on voltage stabilizers; and they're interesting, but I don't know anyone that has tried one. I am currently using an FC alternator and I always have strong voltage, but I'd suggest starting with a brand new battery-to-chassis ground, first.

(Oddly, my avatar only shows as a 5-year member; should be 10 years! Wow, how time flies.)

 

Try unplugging the negative cable on the battery while the car is running. If the idle is unchanged (still sloppy) it is probably a bad battery and the alternator is working overtime to do its job. Or just swap the battery from another car into it and see how that goes.