electrical question

racerboy88 · 01-17-2006, 11:34 PM

Just wondering if anyone else has the same problem. Everytime I use the rear defogger on my 90 LX, it draws so much voltage that the battery gauge drops to 11 volts. Does the defogger actually draw that much power or is there something wrong?
I am going to upgrade my alternator to a powermaster 130 amp model to help the problem.

HoodStrype · 01-18-2006, 09:41 AM

You might have a wire grounded out somewhere, or your alternator and battery may be on the fritz...

Do you have underdrive pulleys? Does your radio, window motors, or anything else cause a similar effect?

racerboy88 · 01-18-2006, 09:01 PM

no pulleys, stereo only when I turn it up. I'm thinking about replacing my ground wires with a thicker gauge

Jeff Chambers · 01-18-2006, 10:09 PM

The rear defogger draws huge amperage. Its on a 30-amp circuit and if you trace the wiring, its at least 10-gauge back to the defogger. As outside temps go down, resistance goes down and the current draw will go up. I think what you're seeing is normal for a rear defogger.

tmoss · 01-20-2006, 08:21 AM

The upgraded alternator will help out a LOT......

Gearhead999 · 01-20-2006, 05:41 PM

Rear window defoggers pull mucho power. Heck, they are a heating grid, like a toaster. Upgrade the alternator, it will help.

vristang · 02-03-2006, 03:12 AM

I have a similar problem, but my voltage gets into the single digits, and I have a powermaster 165A alt.
It seems to be worse when it is colder.

Can anyone explain to me.

thanks
jason

racerboy88 · 02-03-2006, 11:45 AM

how much was your 165amp alternator? It's about $240 CAD for a 130 amp powermaster up here.

Ieatcamaros · 02-03-2006, 10:00 PM

Check into an alternator for a 95GT at the parts store.

racerboy88 · 02-04-2006, 12:42 PM

Quote:

Originally Posted by Ieatcamaros

Check into an alternator for a 95GT at the parts store.

I looked into that but b/c the housing is bigger from the 95, you have do some mods like grinding down my bracket. Of course wiring has to be upgraded.

The powermaster comes as a direct replacement, so it has same size housing. Just the wiring has to be upgraded.

tmoss · 02-04-2006, 05:29 PM

The bracket doesn't get cut much at all - it's very easy. And if your upgrading amperage and not re-wiring with the correct wire sizes, your asking for trouble and possibly a fire.

vristang · 02-04-2006, 09:17 PM

Quote:

Originally Posted by racerboy88

I looked into that but b/c the housing is bigger from the 95, you have do some mods like grinding down my bracket. Of course wiring has to be upgraded.

The powermaster comes as a direct replacement, so it has same size housing. Just the wiring has to be upgraded.

Not my Powermaster! I did have to do some grinding.
I don't remember seeing any high output alts in the stock cases.

I have no idea what the alt cost me, as it was several years ago. I do believe it was more than ~$250.
I can tell you that it costs $100 to rebuild it. This big of an alt does not like to be rev'd to 6k rpm. It can handle it a few times, but eventually blows up.

GhettoPop · 02-12-2006, 12:26 PM

the defogger (90 GT)also puts a big drain on my autometer voltage gauge. so does using the front windshield defroster or "mix" on any fan speed. fan speed #4 (highest) also drains my juice a lot as well. naturally the a/c does damage as well. i put in a 130A PA Performance alternator that i bought for $200 a few years back. the alternator install did require a couple minutes of grinding, very simple. also got a march 1000 pulley setup from PA Perf. (around $100)and they installed the alternator pulley on for me. i also upgraded the wire from the selenoid to the alternator to 4gauge as recommended by PA. ($40?) also replaced the pos and neg battery cables and started cables. ($40?)now my voltage still drops when i use the defogger, but not nearly as much as it used to. the drop is only noticable when at idle, anything over 750 rpm's and she charges great.

racerboy88 · 02-12-2006, 01:47 PM

thanks guys

01-17-2006, 11:34 PM	#1
racerboy88 Registered Member Join Date: Sep 2003 Location: British Columbia Posts: 123	electrical question Just wondering if anyone else has the same problem. Everytime I use the rear defogger on my 90 LX, it draws so much voltage that the battery gauge drops to 11 volts. Does the defogger actually draw that much power or is there something wrong? I am going to upgrade my alternator to a powermaster 130 amp model to help the problem. __________________ 1990 5.0 LX H/B H-pipe w/ flowmasters, Koni shocks and BBK springs.

01-18-2006, 09:41 AM	#2
HoodStrype Rearview Mirror Haze Join Date: May 1999 Location: Huntsville, Alabama...a.k.a. "HuntsVegas" Posts: 387	Re: electrical question You might have a wire grounded out somewhere, or your alternator and battery may be on the fritz... Do you have underdrive pulleys? Does your radio, window motors, or anything else cause a similar effect? __________________ 93 lx Notch 01 GT ...the epitome of Murphy's Law

01-18-2006, 09:01 PM	#3
racerboy88 Registered Member Join Date: Sep 2003 Location: British Columbia Posts: 123	Re: electrical question no pulleys, stereo only when I turn it up. I'm thinking about replacing my ground wires with a thicker gauge __________________ 1990 5.0 LX H/B H-pipe w/ flowmasters, Koni shocks and BBK springs.

01-20-2006, 08:21 AM	#5
tmoss Registered Member Join Date: Mar 2003 Location: Saint Louis, MO Posts: 634	Re: electrical question The upgraded alternator will help out a LOT...... __________________ Tom (Torque) Moss 88Gt 5spd Vert, FLowmaster Catbacks, stock cam advanced 4° @ 108.5° ICL, NMRA prepped GT40P heads 1.85/1.55 valves and 1.7 rockers, MAC P headers Jet-Hot coated, 97 Exlporer intake (ported lower), TB and injectors. 277RWHP/330RWTQ (SAE). http://www.fastlanecars.com/

01-20-2006, 05:41 PM	#6
Gearhead999 Registered Member Join Date: Sep 1998 Location: Oviedo, FL Posts: 992	Re: electrical question Rear window defoggers pull mucho power. Heck, they are a heating grid, like a toaster. Upgrade the alternator, it will help. __________________ "Support our Troops" Dave 1968 Cougar 2004 Thunderbird 2007 F150 Harley-Davidson, SuperCrew 1986 LTD 1997 Ranger 1992 Honda Civic

01-18-2006, 10:09 PM	#4
Jeff Chambers Moderator Join Date: Aug 2000 Location: Milan, OH Posts: 2,699	Re: electrical question The rear defogger draws huge amperage. Its on a 30-amp circuit and if you trace the wiring, its at least 10-gauge back to the defogger. As outside temps go down, resistance goes down and the current draw will go up. I think what you're seeing is normal for a rear defogger. __________________ Jeff Chambers 1990 Mustang GT 10.032 Seconds / 137.5 MPH 14-time Street Warrior World Record Setter CRT Performance 2001 Tropic Green Mustang GT - 12.181 / 113.2 MPH 2002 Ford F-250 Crew Cab 7.3l Power Stroke - 17.41@77.2 "There's nothing boring about a small block automatic shifting gears at 9400 rpm!"

02-03-2006, 03:12 AM	#7
vristang Registered Member Join Date: Feb 2006 Posts: 50	Re: electrical question I have a similar problem, but my voltage gets into the single digits, and I have a powermaster 165A alt. It seems to be worse when it is colder. Can anyone explain to me. thanks jason __________________ Check out my new Mustang website! - Including: TwEECer, EEC-IV, C&L, 351w Fox Swaps, PCV Oil Control, and more. 1990 GT - 408w - 17mpg TwEECer RT 1.30A10 - X3Z - A9L strat. / EA Forged Bottom End / Gapless Rings / CR 8.85:1 / Custom Cam / Ported Trick Flow Heads / Box Upr / Lightning Lwr 17x9 Cobras / Front 255s / Rear 275s / 5 Lug Cobra Disc Conversion / Auburn Ltd. Slip / 3.27 / 31 spline axles / Panhard Rod / Upr&Lwr Control Arms 1987 Red LX - 2.3L - Planning 2.3t Converison

02-03-2006, 11:45 AM	#8
racerboy88 Registered Member Join Date: Sep 2003 Location: British Columbia Posts: 123	Re: electrical question how much was your 165amp alternator? It's about $240 CAD for a 130 amp powermaster up here. __________________ 1990 5.0 LX H/B H-pipe w/ flowmasters, Koni shocks and BBK springs.

02-03-2006, 10:00 PM	#9
Ieatcamaros Domestic Rice really sucks! Join Date: Apr 2002 Location: KY Posts: 973	Re: electrical question Check into an alternator for a 95GT at the parts store. __________________ The sig says it all.

02-04-2006, 05:29 PM	#11
tmoss Registered Member Join Date: Mar 2003 Location: Saint Louis, MO Posts: 634	Re: electrical question The bracket doesn't get cut much at all - it's very easy. And if your upgrading amperage and not re-wiring with the correct wire sizes, your asking for trouble and possibly a fire. __________________ Tom (Torque) Moss 88Gt 5spd Vert, FLowmaster Catbacks, stock cam advanced 4° @ 108.5° ICL, NMRA prepped GT40P heads 1.85/1.55 valves and 1.7 rockers, MAC P headers Jet-Hot coated, 97 Exlporer intake (ported lower), TB and injectors. 277RWHP/330RWTQ (SAE). http://www.fastlanecars.com/

02-12-2006, 12:26 PM	#13
GhettoPop Gimme a Drink! Join Date: Dec 2002 Location: NYC Posts: 694	Re: electrical question the defogger (90 GT)also puts a big drain on my autometer voltage gauge. so does using the front windshield defroster or "mix" on any fan speed. fan speed #4 (highest) also drains my juice a lot as well. naturally the a/c does damage as well. i put in a 130A PA Performance alternator that i bought for $200 a few years back. the alternator install did require a couple minutes of grinding, very simple. also got a march 1000 pulley setup from PA Perf. (around $100)and they installed the alternator pulley on for me. i also upgraded the wire from the selenoid to the alternator to 4gauge as recommended by PA. ($40?) also replaced the pos and neg battery cables and started cables. ($40?)now my voltage still drops when i use the defogger, but not nearly as much as it used to. the drop is only noticable when at idle, anything over 750 rpm's and she charges great. __________________ 1990 GT,stock T-5,K&N w/o air silencer,March underdrives,FMS wires,timing@14*,PA Perf 130amp alt,Steeda Tri-Ax Shifter,Steeda adj quadrant/clutch cable/firewall adj,Centerforce II clutch,o/r x-pipe,Magnaflow SS catback,g-load brace, subframes,Bilstein struts/shocks,Autometer gauges, 136k and running strong!

02-12-2006, 01:47 PM	#14
racerboy88 Registered Member Join Date: Sep 2003 Location: British Columbia Posts: 123	Re: electrical question thanks guys __________________ 1990 5.0 LX H/B H-pipe w/ flowmasters, Koni shocks and BBK springs.

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