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Dodge Dakota Heater Wiring and Heater Issues


biggman100

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Hi guys. This is the one area where i sometimes have issues, and that is in wiring systems. Anyway, the other day the blower motor stopped in my 1994 Dakota, so, i started checking things like the blower resistor, fuses, and relays and such, before i considered the blower motor to be bad. In my search, i found a couple interesting things, the first being, the fuse (#1) in the interior fuse box, and its cavity were melted, and the previous owner had bypassed it by cutting the 2 in and out wires from the fuse box, adding in an add on fuse holder, and connecting the wires to that. Being that it has worked without an issue since i bought the truck a year ago, i dont see that being the issue, i just thought i would mention it.

 

After checking the interior, and power distribution fuses for the blower, both of which are still good, i next checked the relay, and there doesnt seem to be an issue there, so i next went to the blower motor. Before i tore my dash all apart to remove the blower, i unplugged it and jumped it to a charged battery, and it seemed to work fine, so, my next step was to check for power at the plug going into the blower motor, and, i dont seem to have anything at all coming from either the ignition/fuse box side, or the resistor pack side, so i checked for power at the resistor pack, with no luck there either.

 

Now, i am at a loss as to where the power loss could be. In reading the wiring diagrams, which i have attached, it seems to me that the power side goes from the ignition switch, to the number one fuse, then directly to the blower motor, so, if the number 1 fuse is good, then i assume i should have power on one side of the blower motor connector, but, there doesnt appear to be. The other side of the plug, that is connected to the resistor, should also have 12 volts when the key is on, and the blower switch is in any position except off, but, no juice there either. My issue is, basically, am i reading the wiring diagram right, and the blower resistor gets power after it goes through the blower switch on the dash, or am i missing something here?

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You're reading this right, Biggman100.  The resistor is the motor speed controller. Using a digital volt-ohmmeter, I would check the voltage reading at each of the four blower switch terminal connectors (LOW, N1, N2 and HI).  Set the heater blower switch in each of these speed positions, hold the meter's negative probe to ground and the positive probe to the terminal stud for the switch position you're testing.  You should get varied voltage readings for each switch position.

 

You could have a defective heater/blower switch or resistor.  The resistor acts like a rheostat, with each switch position providing more or less resistance.  This translates as the amount of voltage supplied to the blower motor, which changes the motor/fan speed.

 

I'd target the blower control switch and rheostat, since the blower motor itself seems to work fine with direct current applied.  Keep us posted!

 

Moses

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Today i went out, and found the problem. This system is wired the strangest way. The resistor pack, and the fan control switch get their voltage from the blower motor. The way the system is wired, it goes from the ignition switch, to the #1 fuse, then into the blower motor, out of the blower motor, into the resistor pack, and then out to the fan control switch. I did a bunch of voltage tests at the resistor pack, and the blower motor, and got no voltage at either place, so, i decided it wouldnt hurt to run a jumper between the #1 fuse, which is actually bypassed in the fuse box anyway, to the input side of the blower motor, and everything worked. Ultimately, i ended up hardwiring the jumper in to the blower motor, and it seems to be working just fine. I have a 100 mile round trip coming up today, and with the cold, the heater will be on pretty much the whole time, so ill keep everyone posted as to wether it has any other issues.

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