This is out of an 86 firebird with a 2.8 v6

 

U26 is a quad driver. This chip drives the A/C compressor clutch relay, TCC lockup solenoid and the ALDL serial link.

Need to check the coil resistance and wiring for those three items. Odds are the ALDL is OK, unless you tied pin E or M to +12 volts or something.

RBob.

 

Thanks for the help! I understand what you mean by check the wiring but am lost at checking the coil resistance. And when you say tied pin E or M to +12 volts you mean I one of those wires is now getting power and its not supposed to?

 

ALDL pin E or M, sometimes folks will try to enable the fuel pump via a pin in the ALDL connector. Or to lock the TCC, which really gets grounded. So if you did something of this nature, that could fry that quad driver.

As for coil resistance, usually 20 ohms or higher. If it is too low then the high current fries the quad driver. It is just like putting +12 volts right to the driver, it won't like that. The outputs of the quad drivers pull low to ground to turn devices on. So grounding the output won't hurt it.

But if a coil is shorted, then the driver fries. Odds are either the A/C relay is bad, or the torque converter solenoid (TCC) is bad. That one is inside the tranny above the pan.

Note that bad wiring can also cause this. It may be that the wire insulation at the connector is damaged and the wires are shorting together.

RBob.