Blower Motor Circuit Issues

[GSTwithPSI]

I'm having an issue with my blower motor circuit. It works perfectly on all settings except for high. When you turn the blower switch to high, the 10A fuse pops after about 5 seconds.

I have a question about the circuit diagram. Can someone tell me where I can find the electrical system parts location sheet, so I can use the body ground numbers in the electrical diagram to identify exactly where the body ground is located on the car? Here is the link for the diagram click, scroll down to page 198 (heater circuit). I'm looking for the actual locations of body ground numbers #6 and #7.

I'm looking for something like this: click
Scroll down to page 3-14

Thanks!

 

[ktmrider]

Subscribed, I have the opposite problem on 464 ( lowest speed no good, all others fine ).

However once the blower is on it really pulls a load on the charging system, strong enough for engine rpm's to drop significanly before the ISC adjusts.

 

[EROCK970]

Sound like a short to ground. Or a short in the switch. A short to ground blows a fuses as soon as the power is on and a short in the switch can pull to many amps and blow the fuses as well

 

[GSTwithPSI]

Well, here's the deal. The blower will run for about 5 seconds on high before the 10A fuse blows. Additionally, if I drop a 15A fuse in, the blower will run on high without blowing the fuse. I don't want to run with the improper fuse, but it's strange it will run with the 15A just fine. I think it's unlikely I could have a short to ground with these symptoms, but I need to do some more testing.

 

[presterone]

Mechanical resistance can also raise amperage in the circuit. I think there's a mouse nest in your blower motor, or your blower motor is on its way out but check for chauffed or pinched wires first.

 

[GSTwithPSI]

Now that you mention it, I should probably drop the motor and check. I'm looking at the blower motor itself, and it looks like it's only held in place by 3 bolts. Can someone confirm you can remove it by simply taking out those 3 bolts?

 

[FlyingEagle]

Yes, most are designed this way. Lucky you don't have a factory model like some GM's whereby you cut out the prefabbed groove to remove the original blower motor, and use a supplied bracket and screws to hold the new motor in place; the holes are already there! Yes, so have at it.

 

[GSTwithPSI]

^^^Thanks!

 

[theevozero]

A short to ground will not even allow the blower motor to turn on, with no consumer in the circuit. Your likely cause is high resistance in the circuit somewhere (power or ground side) or as mentioned above, mechanical resistance in the blower motor itself. High resistance can be caused by loose terminals and connections or a spent(a wire that has been hot too many times) or old wire(basically the same thing). It is likely in your main blower motor power wires. A basic dvom and a circuit diagram will aid you in finding the problem quicker then anything. You can also measure your current in your blower motor circuit, but you already know it's over 10 amps.

You can also do a voltage drop test or a loaded bulb test. Basically measuring a circuits ability to carry a electrical load. You can have a wire with okay resistance, but has a massive voltage drop. If your circuit test fine, its probably the blower itself.

 

[ktmrider]

Here's the highly likely culprit on mine ( no low speed and high current draw ):



Here is the thread that shows blower resistor location: click

Heading out now to find a replacement, will report back shortly.

 

[ktmrider]

Got a new unit at Vatozone, $25. Woulda been at least $10 at UPI between the part and entrance fee, no brainer once I found the new one.

Cleaned out a limbs worth of leaves from the squirrel cage. Installed the resistor unit and tested, all speed present and accounted for.

Everything reinstalled, tested in the driveway and on a 10 mile jaunt. Previous high load/RPM drop is now gone.