Question about 1987 Nissan 300ZX

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Low Voltage At Heater Blower

Heater blower stopped working. Pulled the blower and it tests ok but at the input terminals I read .15 V with the computer controller on economy with low fan and .46 V when on high fan. I traced the wiring up to a relay/diode combination above the glove box. Wondering if anyone has experienced this and can identify whether the relay or diode assembly would be faulty or if its something else.

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  • lvewire Feb 08, 2009

    Its an 87 300ZX. It seems like the blower relay/diode assembly was designed to be grounded on the bottom but I didn't find a connection to ground. Could that be the problem?

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When you tested the voltage they mean basically nothing without a load. No automobile fan will run at 1/2 a volt. Put the blower back into the circuit and retest the voltage. If you did indeed check with the blower in circuit, you do have a problem with the supply voltage. I would need to know what make, model and year to tell you more. As a temporary fix, you can rig a switch to the blower to supply 12 volts directly to it. It will run on high whenever you have it on, but it will work until you can trace back to where the problem is.

Posted on Feb 08, 2009

  • charger10 Feb 08, 2009

    Absolutely. If it isn't properly grounded it won't work at all. Try running a jumper to any available ground source and try it again.

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Here is an exploded view of the HVAC box. The resistor is #63 in the picture and the actual part may appear slightly different:

spacer.gif 1100_024_0003.gif spacer.gif spacer.gif View Full Image spacer.gif


If any issues such as no voltage at blower connector or damaged or melted connector at the resistor then let me know.

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