Help With Relay

Hello friends at rec.autos.tech,

I have a heater blower motor that draws approx. 25 to 30 amps. When the
vehicle is running at idle, my volt meter reads just under 14 volts. When
the blower motor is placed on high, there is a significant voltage drop on
the gauge, in the 11 to 12 volt range. I connected a relay using a direct
12 volt source from the battery and grounded the relay. This energized the
electromagnet which closed the primary circuit. I connected the other end
of the relay to the heater blower motor, started the vehicle, noted that the
volt meter read just under 14 volts and turned on the blower motor. The
volt meter demonstrated no appreciable drop (moved downward slightly). At
this point I figured I had the problem solved so I screwed the relay to the
firewall using the same screw to supply the ground for the relay, connected
the 12 volts from the key-on circuit (only hot when key on) and the other
end to the blower motor. I started the vehicle, the voltmeter showed just
under 14 volts, I then turned on the blower switch and the needle dropped
appreciably in the 11 to 12 volt range. I assumed that initially the
electromagnet had to be closed and thought the key-on circuit would be fine
for this purpose since the relay would only be energized when the ignition
was on. The direct 12 volt source I used initially was supplied directly
from the battery using 12 gauge wire. When I attempted to make the
connection permanent I was using 18 gauge wire through the ignition switch
key-on position. I was under the impression that the purpose of the relay
was to allow low amperage initially to close the electromagnetic switch and
the relay would handle the higher amperages going to the blower motor. This
one's got me stumped, any help would be appreciated.

Thanks,
Craig

On Sun, 20 Mar 2005, Craig wrote:

> I have a heater blower motor that draws approx. 25 to 30 amps.

Replace the motor. That's GROSSLY excessive.

Daniel J. Stern wrote:
> On Sun, 20 Mar 2005, Craig wrote:
>> I have a heater blower motor that draws approx. 25 to 30 amps.
>
> Replace the motor. That's GROSSLY excessive.

All the Fords I've noticed have a 25A to 35A fuse or breaker in that
circuit.

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