backtothe80s

Hi all,


As per the title, my electrical system is lazy. The voltmeter on the dash barely hangs around the 13v mark and often drops a bit below that with headlights and AC on. Applying the brakes seem to cause a significant drop (0.5v or so). It's noticeable enough that you can hear the fuel pump (walbro 255) change pitch, especially after driving for about 20-30 mins in warmer weather (above 90f).


Overall, power accessories seem to be slow. Most noticeably the fan motor and power windows. I know the windows are slow by nature, but it's worse than it used to be. I feel like there's a bigger problem than just weak motors.



I'm running a newer battery, powermaster 140 amp alternator, a 2 gauge ground cable, and a 0 gauge postive cable with a heavier gauge wire to the alternator than stock. It uses a larger side post terminal. I've cleaned the headlight grounds, brake light ground, and the connections to the starter.


I know the wiring in these cars was not the best to begin with. That said, are there any grounds I should check and clean up? Are there places where voltage drop is more likely to occur on these cars? What about the brake lights? Would new terminals help? New bulbs?


I'd rather deal with root causes than compensate. Suggestions are appreciated. Thanks in advance!

Drew

iTrader: (58)

I'd start with the factory power distribution and ground diagrams and verify your connections. With a good battery, cables, and a properly functioning 105amp alt, you shouldn't have those problems. By 89 the electrical system wasn't bad at all.

backtothe80s

Good call. I'm thinking there's unwanted resistance somewhere in the wiring/connections, possibly before it gets inside the cabin.

OrangeBird

iTrader: (1)

My suggestion ?

Only one . Get and use a real voltmeter for any and all measurements you want to be accurate , and disregard the factory dash gauges as any kinds of serious , precision measuring equipment . You may find with a real voltmeter (Fluke , Simpson , etc) your voltage is actually OK , no need in chasing one's tail over a problem that may not exist (the suspected low voltage) .

backtothe80s

I know the dash voltmeter isn't a precision instrument. I measured the voltage at the battery with the engine running and it was, as I recall, in the high 13s/low 14s. That's good. I'll measure it again, but I recall a pretty significant discrepancy between what my meter showed on the battery and what some of the power accessories are showing (0.5v or more). That suggests there's voltage drop somewhere.



I'll recheck and report back. Thanks.

backtothe80s

Update: I cleaned up some of the grounds, specifically G200 at the dash and G112 behind the LH cylinder head. Gauge seems to be closer to the voltage measured at the battery and alternator when the engine is running (14v) and accessories/lights are off. I'll have to check the taillight circuit and see what's going on. I suspect some corrosion at the bulbs. I noticed that the fuel pump sound changed when I applied the brakes. As far as the slow windows, lazy power door locks, and weak blower, it's probably the age of those motors that needs to be considered. Thanks guys.

zed-028

My alternator had the stock charge cable attached to it. skinny and inefficient. I took the cable to an auto electrician to make up a new one. fluctuations went away.

backtothe80s

I built a positive battery cable with 0 gauge cable and a 6 gauge wire for the alternator. To my surprise, it made little difference, but I'm glad it sorted out yours.