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94 S10 Blazer strange heating/AC problem

I have a 1994 S10 blazer with A/C.

About a week ago, all my heating and cooling went out. I unplugged and checked the voltage at the red wire going to the blower motor, showed 12 volts when the fan controls were on and 0 when they were off, ordered a new blower motor, installed it...and nothing.

When the positive lead is disconnected from the motor, it shows voltage when the fan controls are on. The wierd part is, if you slip a multimeter probe into the cable hood while it is attached to the motor, it shows 0 volts no matter what.

And the even weirder part is that both of my blower motors, when hooked up with jumper leads to a 12v power supply, power up and work great. It seems like a problem with a relay or a wiring issue...but I figured I'd ask here before I started ripping stuff apart.

I thought maybe the resistor pack was dead, but even on the highest settings there is nothing (highest setting should bypass the resistor pack). Has anyone heard of anything like this before?

Reply to
Matt
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All it takes to show volts on the meter is a few milliamps of current.

It may show 0 volts with a load if a connector is corroded somewhere.

How about getting a small trouble light , and repeat your test - especially in the connector pins, but unplugged. See if the lamp will come on, not connected to the motor.

I would bet not, from what you've described. You'll have to find where it's losing current-carrying capacity. Sometimes a loose pin in a connector will do it, but usually those get hot enough to leave visible evidence (turns brown). Could be one of the relays under hood or in the glove box. Could be the fuse is corroded/ dirty / loose.

Reply to
Miller

You were dead on - a corroded pin in the relay harness was the culprit. New harness was $6, soldered it in, everything works great.

Reply to
Matt

Good deal - cheap and relatively easy fix.

Reply to
Miller

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