[mysweetstang]

im new to this site but not new to mustang's. i have a 91 mustang gt. im having this problem that i cant seem to figure out, here it goes. when i have my head lights on and im drving my car my volt meter goes way low but still in the normal range (around the O on the meter). When the volts go down this low i get a real bad shaking only at 1500rpm one it goes below 1500rpm its fine and above 1500 its fine also. it shakes like im in a high gear going to slow. What are some things i could be looking out for here i need help! I have been having a problem with something in my wires for a while cause when i have my blower motor and head lights on i get very little charge but if only one of the things is on im fine. this problem just started with the shaking and low volts whit the head lights on. PLEASE HELP im going nuuts

[dcraig8]

check your main engine grounds and accessory grounds,also look at your plug wires and make sure they are not laying on or too close to your headers

[stang fanatic]

sounds like alt is going bad...cant produce necessary amperage to charge batt and run all accs incl. the ecc. engine is misfiring due to low voltage and clears up cuz the alt produces more at high rpms. need to get load tested....load test batt too...bad batts are known to be root cause for alter. failures

[mysweetstang]

its acting weird though like when i go under 1500rpm it runs fine with no shaking. its only at 1500rpm it shakes. i will deff check the alt. and batt out. im also goin to look at the wires. thanks guys!

[stang fanatic]

sorry...misread what you posted. thought you said shakes under 1500. does sound more ignition type issue

[mysweetstang]

so what shouldi i go and check out first. i looked at my wires and there fine. maybe my coil? or am i lookin at maybe a cap and rotor. if im lookin at a cap and rotor anyone here got an msd up for sale?

[IcantDo55]

Put a 140 Alt in there and solve that FOX issue once and for all!

[stang fanatic]

Id still ck out the charging system and batt first...you need the alternator load tested to see how many amps its putting out. 12 volts is 12 volts, but theres a problem when its achieved only through 40 amps of output under 100 amp load versus being the rated 100 amps (treoretical numbers...dont know the rating of your alter.). In other words...your alternator should not produce less than 15% of its rated load when placed under full load.

[IcantDo55]

Originally Posted by stang fanatic dont know the rating of your alter.). In other words...your alternator should not produce less than 15% of its rated load when placed under full load.

Its a 60amp unit. Set of roadlight s or a stereo and its over its limit.