macho_mango

Hi all,
I have a 1984 Porsche 944, n/a.
Its been running great for the last couple of years, save for some water leaks (which I think I have finally solved, please god).
But I recently developed a new problem.
I've noticed that when I drive the car for a bit and its gotten warm, I start losing electrical out put.
I've had the alternator changed, and still no luck. WHen the car is cool, seems ok, but once its running for a bit, and I start turning on lights/fan/radiator/heat/etc.
my voltage drops down, even into the 12s or high 11s.
Does anyone have any ideas????
Please help!!!!

spoolinturbo

where are you reading your voltage from? in dash gauge?

macho_mango

The dash gauge just has a warning light, so I took a portable digital voltmeter to read output from the cigarette lighter.

spoolinturbo

check your output of the alternator

check your batt voltage (car running)

then keep a voltage meter on the battery with engine off.

your battery may not be holding its charge well at all, and u are probably running a lot of cars power, off a dying battery.

one of my other cars did that and i was changing voltage regulators, checking grounds, testing alternator when i should have just started with a volt meter =/ the battery was to blame.

macho_mango

My alternator output seems ok, its sitting about 14 volts.
I tried measuring the voltage off the battery and it was about 12.4 with the car off. Is that ok?
I've got an interstate 85 battery, but I'm thinking of switching to Optima. Any experience there?

spoolinturbo

optima is good.

sittin at 12.4 with the car off is good.

hmmm maybe it has a bad recharge rate under load, i would have it tested before u spend the money on an optima.

macho_mango

Its odd that it only happens once the car gets warm. I'll check it out tmw.
Thanks!

944Ross

Check your belt tension. As the belt gets hot, it grows, loses tension.

ballysdad

+1 on the belt tension and one other note. You can check alternator voltage with a voltmeter and read 14.7v ect (over battery voltage) but that will not test amperage output. Take you car to Sears and for about $16 they will check your starting and charging system. Most importantly they will check amperage output with a shunt installed to read output. An alternator rated at 60 amps and only putting out 25amps will still read 13 or 14v on a multimeter.

87 944 C

12.4 is a lil less than 75% of your batteries power. if it's a maintenance required battery, lift to 2 panels off the top and check electrolyte level. also get a battery load test done.

if unfamiliar with that test, a vat is required(a shop, as they can cost mega bucks), they'll put a load of like 112A on your battery for like 15 seconds at most, and then they'll check the battery voltage again, if it falls below 9.6V then you need a new battery....**** i actually learned something from that electrical auto class.


also depending on the voltmeter you use the battery may damage the fuse inside it, so be careful with em...though fuses are cheap enough.


also do check alt belt, bad tension could cause it to not recharge as well as it should

Vonov

Sounds like the engine to chassis grounds may need cleaning. As you drive, any ground which has corrosion or is loose will begin to develop heat; as the heat begins to build, so will the resistance across the connection, causing more heat, which will also increase heat in the cable because the load begins to increase, further increasing resistance, causing a further drop in voltage, diminishing the "apparent" alternator output. You may also want to consider installing additional ground straps from negative side of battery to chassis, and from engine to chassis.

sj340

If it does turn out to be the battery,be careful with the optima battery.
Unless the battery compartment is different on an 84,the battery will be too tall.I bought one for my 87 and installled in before I noticed.Had I not noticed before I closed the hood it would have dented the hood.

bearone

a hi rate discharge tester is under $20 most places, i've had one for years and the batt needs to be fully charged before test with a charger, driving won't bring it all the way up..

87951
95sl320 dd

87 944 C

vat is different than a high rate discharger, high rates can do a couple but a vat can do like 5 that i know of, but i'm still learning.

944Ross

What is a "vat"? Volt-Amperage Tester? What do you mean, "high rates can do a couple, but a vat can do 5"? A couple what?