1988 hilux, when i,m driving with the heater fan on high and turn the headlights on truck starts to sputter and jerks almost to the point of stalling turn the headlights off to just running lights and heater fan on high truck runs smooth or i canturn the heater fan down one notch with headlights on runs smooth. . can,t seem to have the headlights on with the heater fan on high together.any ideas. ps. had the alt. tested on start 14v turn lights on dropped to 13 then up to 14. on idle when i turn the lights on fan speed will decrease. thanks

 

bad ground?? dirty connection at battery?

 

Yea do a Battery test and charging system test. Make sure there both working as they should be.

 

check grounds and the alt ground.

 

most likely its bad ground or the alternator needs to be replaced, and since its a 1988 late model the voltage regulator is inside the alternator so, just change the whole thing. also check the batterys amp levels just because it shows 12v+ doesnt mean its a good battery.

 

ground

thanks guys regrounded body ,frame motor , worked like a charm