QTR FMS

Hi,

i have an issue with my voltage dropping to 12.8 or even below when my fan is on and it keep killing my battery, the alternator is from 19370821 i think, its wired with one wire from the engine harness, the fan is from ford taurus which pulls 30-40 amp.

this voltage drop causing all kind of issues and its bothering me,

i dont think its the alternator as its not that old barely used less than 1000 mile on it, it been in storage most of it time mostly of because of this issue, could it be the one wire connector or maybe psi thin alternator to starter wire which is what powers the whole car or is the taurus fan draw too much amp for the alternator

G Atsma

Alternators have been known go bad ANY TIME from new. Yours is not above suspicion.

GMTECH4

A bad battery will put a heavy load on a charging system. Don't overlook the basics, like clean/ tight terminals, good grounds, no missing grounds, corrosion etc....

FormulaBoat

iTrader: (1)

Agree on battery health. If it is 5 years old or more, ditch it. If it has went totally dead several times, regardless of age, ditch it.

You can run a modern GM alternator to add a lot of extra oomph. I just did on my 5.3L Colorado, boosted alternator by 100amps production rating just by using a current model one, all direct from GM or Rock Auto, not a black magic shop that says high output. My alternator went from like 140 to 240 amp rating. Same size, same connectors, same everything. Plug and play. Hate to hear you not using the ride because of it. I work for the company that makes the current GM LS mass production ones, so easy for me to know what fits/works. Mine was truck accessory drive, FYI.

Project GatTagO

iTrader: (7)

I would also evaluate how everything is wired.

Andrew

00pooterSS

iTrader: (40)

Sounds like a weak alternator that can't handle the additional electrical load.

I have a 50 page alternator thread full of my posts and other peoples posts about alternators failing right out of the box and all the replacement alternators for F bodies being absolute junk.

Upgrade to the 145 amp truck alternator and be done with the issues.

https://ls1tech.com/forums/generatio...failure-s.html

dixiebandit69

You have VASTLY underestimated the amperage draw of a Taurus fan. Those things pull about 80 amps when running at full speed, and can spike up to about 100 when turning on; the factory programming for those cars would turn the fan on at partial power in order to keep from overloading the system; I believe they called it a "soft start" setup.

I ran a 2000 Mustang GT fan* on my '89 Firebird because I happened to have one lying around. It cooled great, but I had a lot of problems with relays not being able to handle the amperage, and the factory 105 amp alternator couldn't cut it, so I had it upgraded with a 160 amp kit. This fan immediately melted the factory fan relay, and I dicked around with some 70 amp universal relays for awhile, before finally settling on a Bosch 75 amp relay with 8 gauge wiring.

*Taurus, Mustang, Crown Vic, Thunderbird, etc. all use the same fan with different shrouds.

LilJayV10

iTrader: (39)

To run a fan that big I would probably use an old school Ford starter relay or a bad *** SSR

00pooterSS

iTrader: (40)

Ford starter relay is a really good idea. It can carry a TON of amperage and is super easy to install.

FormulaBoat

iTrader: (1)

Not sure Ford fender type starter relay is continuous duty rated?

00pooterSS

iTrader: (40)

Never even thought of relays only being rated for momentary or continuous. Interesting.. I guess I foolishly assumed if they can pass the power they can pass the power.

LilJayV10

iTrader: (39)

Relays are rated that way.

I believe what he was referring too is the Ford solenoid is just that, a solenoid, which is a relay, low current controls high current.

To answer the question what the Ford solenoid is rated at, that I don't know. I've been using it to control high amp fans for years as many people have.

QTR FMS

i know for sure that its not the battery fault as it would die when its less than week old because the fans discharge the battery and the alternator cant keep up

QTR FMS

isnt the lsa ls7 ls3 alternator a modern one? im using the gen iv fbody alternator

QTR FMS

its wired with psi harness, and volvo relay and relocated battery but the ground goes to the chassis not the block

QTR FMS

i will replace it but do you know if the truck alternator would fit on fbody belt assembly?

Project GatTagO

iTrader: (7)

I would run a ground from the battery, directly to the engine block. If the alternator plug is 4 pin, I would add a wire from the S terminal to the point where your fans are getting power, as this is likely the point in the system that sees the biggest voltage drop when the fans kick on. Having the S terminal wired there will boost alternator output when the fans kick on.

Andrew

QTR FMS

im not sure where people getting 80 amp i have tested it with multi-meter when it first turn on it spikes to are 40amp and then goes down to 30amp, my mechanic installed 30amp as it only spikes to 40 for few seconds and it did work for few days but then i blow a fuse and went to 40amp fuse and its working fine with 40amp,, and about the relay im using volvo relay with 10 gauge wire to the battery and 10 gauge from the alternator to the starter

QTR FMS

i have a feeling the wire on the s terminal would solve my issue it if would boost alternator output.

do you know how much the alternator output with and without the s terminal ?

Project GatTagO

iTrader: (7)

I do not know exactly. What I do know is that I have two swapped cars. One (70 GTO) has just the L terminal wired to the alternator from the ECU (GMPP harness). The other (67 Cougar) has the S terminal wired along with the L terminal. When the GTO fans (dual Spal) kick on, I see a noticeable voltage drop on the voltage gauge. With the Cougar, I barely see any voltage drop, even when the fan (C6 Corvette fan, 32 amp draw at full speed) is at full speed (PWM fan control).

I would still add a ground to the block from the battery.

Andrew