77 with internal regulator

[grantf]

Having some volt/ amp issues with my car. It runs and starts great but at night with the lights on the volts drop to around 11, during the day when driving around 3000 rpms the volt gauge climbs to around 15.5. I am thinking this is a regulator issue. sometime before I bought the car it had been converted to an internally regulated alternator, which I have since replaced. Wondering if the conversion was done correctly. Note only two sets of wires are jumped and the color match up looks odd.

Edited May 30, 2011 by grantf

[Zed Head]

The voltage meters on these cars are typically inaccurate, so the 15.5 reading may not be right. Have you had a voltmeter on it at high RPM? I wouldn't trust the stock in-dash meter. They can be adjusted via the screws in the back though for future use, but you'll still need an accurate volt-meter to do it.

The wiring looks typical of someone jumping the plug instead of cutting the wires. You can check Blue's site to see if the colors are matched correctly. They don't match by color, but by function,and there are several "extra" wires afterward.

Is the "11" reading (accurate or not) at idle, at night with the lights on? Or is it while driving? It sounds more like a weak alternator, low idle speed, or too much current drop through dirty connections. The Z alternators put out just enough amperage at idle to get the job done, if everything is clean and working correctly. Even an extra 500 RPM of idle speed can make a difference.

I have also found that a 10 year old factory alternator from an old parts car performs better at idle than a brand new rebuilt parts store alternator. The parts store alternators are of generally low quality. I had mine die within a year.

[grantf]

No I have not performed an accurate reading with my meter yet (need another body, longer leg, or third hand). And I understand that the in dash gauge is inaccurate. I have compared the 78 and 77 wiring diagram and it does look like the correct wires have been jumped only that there is an open blue and an open black. The black does not concern me as it was for grounding the old regulator but the blue has me wondering. Yes I do have a little bit of a low idle speed, but with the lights on I only get enough amps at around 1500 rpm. hmmm I am going through cleaning connections but no real change yet. I hope I do not have to make another alternator swap.

[Walter Moore]

What kind of lights do you have, and what wattage are they? Have you added any power hungry accessories, like electric fans? The ZX alternator doesn't put out very much current at idle. I have the 70 amp ZX Turbo alternator, but at idle with the lights on if my high current electric fan kicks on the voltage drops to battery. I have street legal 55W/65W H4 bulbs in my headlights by the way, and an after market volt meter that I have verified against my multimeter.

You need to check the voltage readings with a reliable volt meter. If you really have 15.5V at speed then the regulator is shot and you will boil your battery.