Blower motor problems

[Paulonline3d]

My Delorean is working after a lot of reading and repairing from the forum. However, my AC blower fan is acting up, and can't find any similar issues from other threads.

I have the blower motor out so that I can see its operation, and it seems to be underpowered. On fan speed 1, no operation, motor doesn't turn. Fan speed 2 looks like motor is barely trying to turn. Fan speed 3, motor spins, but looks slow. Fan speed 4, motor spins for 5 seconds, and then circuit breaker pops, shuts off, then on, then off...

I have already replaced the resistor pack. I did swap in a replacement blower motor, which did the same thing, so not the motor itself. I put a voltmeter on the motor while attached, and readings seem very low. On fan speed 4, voltage was about 5V (thought it should be 12V).

Any ideas on what is causing the underpowering of the fan? Would like to have AC working again, now that I've gotten it drivable. Thanks for your help.

- Paul

[David T]

Check the ground wire, make sure it has good connectivity to ground for the motor.

[Paulonline3d]

Check the ground wire, make sure it has good connectivity to ground for the motor.

I used my jumper cables to connect a good ground from the engine bay to the screw on the blower motor that has the ground connection. It may have made things worse, but still similar. Also sanded off the paint where the screw connects to make sure is was connecting to bare metal. Same.

[TTait]

Use good jumper wires to test either one or both of your blower motors directly to the battery. Best practice would suggest that the positive wire would be fused. See if the blower motor operates properly when the wiring is perfect just to ensure your blower(s) are in fact good.

[Elvis]

The Circuit Breaker pops ?
Then meaure there the voltage and replace the 40 year old $5 part if needed.

[Paulonline3d]

Use good jumper wires to test either one or both of your blower motors directly to the battery. Best practice would suggest that the positive wire would be fused. See if the blower motor operates properly when the wiring is perfect just to ensure your blower(s) are in fact good.

Connected blower motor directly to battery (briefly), and it spins up like a champ! But connected in place, behaves anemic.

Got a 30A circuit breaker, and hot wired it in place of the old 25A (different connectors, so required some creativity). Same action on speeds 1-3, and now 4 does not work at all. Will take another look to make sure I put circuit breaker in properly.

No joy! Thanks for your continued help.

- Paul

[Bitsyncmaster]

Connected blower motor directly to battery (briefly), and it spins up like a champ! But connected in place, behaves anemic.

Got a 30A circuit breaker, and hot wired it in place of the old 25A (different connectors, so required some creativity). Same action on speeds 1-3, and now 4 does not work at all. Will take another look to make sure I put circuit breaker in properly.

No joy! Thanks for your continued help.

- Paul


Speeds 3 and 4 run though two relays used to reduce current through the fan switch. Speed 4 runs power directly to the blower (no resistor).

[Paulonline3d]

Speeds 3 and 4 run though two relays used to reduce current through the fan switch. Speed 4 runs power directly to the blower (no resistor).

So on speed 4, should I be seeing 12V at the blower motor? Mine seems to have only like 5V on speed 4, and all the speeds look under powered. Wondering what would cause a low voltage going to the blower motor on all speeds. Thanks.

- Paul

[Bitsyncmaster]

So on speed 4, should I be seeing 12V at the blower motor? Mine seems to have only like 5V on speed 4, and all the speeds look under powered. Wondering what would cause a low voltage going to the blower motor on all speeds. Thanks.

- Paul


You should see close to battery voltage. If your only seeing 5 volts than your circuit breaker of a bad connection is probably dropping the voltage. What does your dash voltage gauge read with the headlights on (for a load).

[Paulonline3d]

You should see close to battery voltage. If your only seeing 5 volts than your circuit breaker of a bad connection is probably dropping the voltage. What does your dash voltage gauge read with the headlights on (for a load).

Didn't get to check that yet, but I did check the battery voltage by itself with a voltmeter, and it was 11.97V.

- Paul

[Elvis]

basic electrocnis. You have avoltage drop on a resistance somewhere in your wiring.
Circuit Breaker was the first try - but what voltages you measure there ?

could also be a bad crimp.
or a wire breaking
Could also be a bad Ground connection of your fan.
That's all easy to measure with a multimeter.

Which Ground do you use for your multimeter ?

[Paulonline3d]

Okay, got a chance to get back at it and replaced the old 25A circuit breaker with a new 30A. Cut off the clip-on connectors and put in ring connectors to insure good connection. Tested it out, and still same problem. On speed 4, still runs for about 5 seconds then circuit breaker pops, resets about 5 seconds later, then pops, etc.

I have the blower motor out while running, and the resistor pack. I can actually see each individual resistor come on at each speed, and start glowing within 5-10 seconds at each speed. Speed 1, even though the blower is not moving, I can see the resistor heat up and glow. Then turn to speed 2, and motor twitches momentarily, and different resistor starts to glow. Speed 3 has the motor moving, but seems very sluggish, and the 3rd resistor starts glowing pretty quickly. Speed 4 has all resistors off, motor spins faster, but then circuit breaker pops after 5 seconds.

I know it is not the motor, since I swapped in a new one and same results. Not the circuit breaker since that has now been replaced. Not quite sure where to go next. Hoping you guys have some more ideas. Thanks.

- Paul

[Paulonline3d]

Check the ground wire, make sure it has good connectivity to ground for the motor.

Here's a curiosity... I was checking the grounding to the fan again, used jumper cables to go from battery negative to ground screw on blower fan, and it actually performs worse!

I checked continuity with a multimeter between blower fan ground screw and stainless steel exterior, and got good continuity.

Any ideas? Thanks.

- Paul

[Rhye]

I see 2 options: either both blowers have shorted windings/worn bearings or there's some current leakage in wiring. Have you tried running the blower with filtering capacitor disconnected?

64638

If there's no change, I'd measure the current draw of the blower powered directly from the battery (~30A range meter needed) - should probably be less than 20A if the blower's good.

[Bitsyncmaster]

I see 2 options: either both blowers have shorted windings/worn bearings or there's some current leakage in wiring. Have you tried running the blower with filtering capacitor disconnected?

64638

If there's no change, I'd measure the current draw of the blower powered directly from the battery (~30A range meter needed) - should probably be less than 20A if the blower's good.

+1
Looks like you have no other options but to measure the current. Not many multimeters work above 10 amps so you need to find a DC clamp on type current meter. You just lamp it over the one wire going to the fan motor to read current. Make sure it's rated for DC current. A lot of them only work with AC current.

[David T]

Sounds like the motor (both of them) is drawing too much current. From your description all speeds work. The one that concerns me teh most is #4, full speed. For that speed there is no resistor but it pops the circuit breaker. That means you are drawing over 30 amps, WAY too much. I don't need a meter to figure a new 30 amp breaker is popping and know that you are drawing at least 30 amps! Get another fan motor.

[Elvis]

Here's a curiosity... I was checking the grounding to the fan again, used jumper cables to go from battery negative to ground screw on blower fan, and it actually performs worse!

I checked continuity with a multimeter between blower fan ground screw and stainless steel exterior, and got good continuity.

Any ideas? Thanks.

- Paul

Hi Paul - what menas - runs worse ?

Continuity with a multimeter ? We are talking here of resistances of below 1 Ohm, more like 0,0x Ohm.
You probably don't have such good measuring devices.

Measuring resistance AND (more important) inductivity of the motor while comparing it to a known good one would help.
Or replacing the motor again.
Is it the correct motor ? Did you perhaps get a 6V version ?
Pics ?
Current clamp is also a very good idea.

[Paulonline3d]

Okay, got some work done this evening. Bought a clamp-on meter to test DC amps pulled by blower motor (as suggested). Put meter on blower motor hooked to car, and on speed 4, hits 115A for about 3 seconds before circuit breaker trips. So definitely not good!

But, hooked blower motor straight to battery, and it spins up super easy, and clamp-on meter reads 8-9A. What gives?

Don't think it is the motor. Where should I be looking between the battery and the blower motor?

Thanks.

- Paul

[Paulonline3d]

Holy crap! Problem solved!

Someone who worked on the car in the past, put the wrong clips on the wrong terminals. Big fat pink wire with black strip was on the ground terminal. Switched that to the main terminal, with all others on ground terminal, and now works great on all speeds.

I like simple solutions! I just wish it didn't take me several weeks to figure it out. Thanks for your help, and patience. Maybe this will help someone else in the future to save a couple weeks.

- Paul