aa7kn

I have a 1991 4.0L man. trans. cherokee, the balast resistor that helps keep the fuel pump at a constant voltage gets very very hot. so hot that it will burn you in a micro second if you touch it. is this normal ? any one out there ever notice theirs getting hot ? I did some voltage checks with my multimeter and I have 12.8volts on one side and 5.5 volts on the other...this seems low because I thought the fuel pump ran at 12 volts ??? any light on this subject would be great, and thanks in advance.

tjwalker

It's a resistor so you're going to have voltage drop on the other side.

That resistor is there only to reduce "noise" on the fuel pump circuit.....

Do you have any symptoms? Was wondering what brought you to checking your resistor.

The_ocho

When the electrons go through the resistor they are slowed down and transfer energy to the resistor in the form of heat, making the resistor hot. The heat is the resistor limiting like its supposed to

Radi

That resistor should measure somewhere in the neighborhood of 1.1 ohms. What's yours?

If yours measures OK, you may have something drawing excessive current.
OTOH if yours measures substantially more than 1.1 ohms, that increase is probably the cause of the heat.

Bustedback

It's a restistor, resistance makes heat, it is normal for the ballest resistor to get hot.

cruiser54

IIRC, the power is reduced from 12 volts to 10 volts across the resistor. 5.5 seems awfully low..