Blower motor troubles

[95_silverado]

I just replaced my blower motor, blower motor reisitor, and the relay on my 95 c1500 a little over a month ago. A week ago it just cut out on me. I have no clue what could be causing it, I tested all the new parts that were installed. The ground to the motor was crusty but still the motor will not blow air. I'm tired of shooting in the dark and need help.

 

[east302]

Check the voltage on the wire that plugs into to the blower. See what it reads at various blower speeds - it should go up to battery voltage on high and be less at decreasing blower speeds.

Compare using a chassis ground and the ground wire from the blower to rule out an issue with the ground wire.

If you have no voltage regardless of the selected speed, then it is upstream and probably at your panel blower switch. On the later ones (96+) the blower switch connector likes to melt and cause issues but I’m unsure if the 95 had the same connector or not. Take a look, it’ll be noticeable and your blower switch pins may have melted plastic on them.

Edit: here’s a diagram for a 98. Make sure that your 25A fuse on the dash side panel isn’t blown if it doesn’t work at any speed.

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[The_Full_Monte]

I just replaced my blower motor, blower motor reisitor, and the relay on my 95 c1500 a little over a month ago. A week ago it just cut out on me. I have no clue what could be causing it, I tested all the new parts that were installed. The ground to the motor was crusty but still the motor will not blow air. I'm tired of shooting in the dark and need help.

Same-zies, man. Same-zies. Blower, blower motor, grounding wire, blower motor resistor, HVAC control module, clean/clear evaporator coil and still running at ~50% of maximum speeds (in other words, when I have the blower selector on "Hi," the blower is running at about medium speed. I wish I had the money to do a frame off resto mod on my "99 K2500 Suburban, as it has a long laundry list of misc. things that need to be addressed.

 

[Schurkey]

That wiring diagram doesn't show the thermal limiter that was part of the blower resistor on my '97 K2500.

I've seen multiple blower resistors where the resistor coils were fine--the thermal limiter had popped; and that results in no blower except on high speed.
Photo--blower resistors from a '98 Monte Carlo. Thermal limiter tucked under the resistor coils.

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No doubt thermal limiters are available from Digi-Key, Mouser, and similar electronics stores. I wouldn't know what specs to ask for, though.

I knew there was trouble when the smoke was coming out of the dash vents. Blower motor burned up, taking the 50-amp ma_xi-fuse, the 25 amp blower fuse, and the thermal limiter on the resistor array with it.

 

[someotherguy]

The fan switch and harness to it are known for burning up on the 1995-up controls. They are replaceable separately; no need to replace the entire control. Pigtail is a bit pricey as they always tend to be, but the switch is fairly cheap. Give 'em a look. Be careful pulling the control head as the plastic is usually very brittle, especially on the tabs to release it from the dash.

Richard

 

[The_Full_Monte]

The fan switch and harness to it are known for burning up on the 1995-up controls. They are replaceable separately; no need to replace the entire control. Pigtail is a bit pricey as they always tend to be, but the switch is fairly cheap. Give 'em a look. Be careful pulling the control head as the plastic is usually very brittle, especially on the tabs to release it from the dash.

Richard

Yes - I pulled my my old HVAC control module and replaced it with a new AC Delco (OEM) HVAC control module. When I pulled the old one out, the plastic was literally crumbling in my hands and the tabs broke off just by looking at them. Not a big deal. The new module has all-new plastic with tabs, so it snapped in tight.

 

[someotherguy]

Yes - I pulled my my old HVAC control module and replaced it with a new AC Delco (OEM) HVAC control module. When I pulled the old one out, the plastic was literally crumbling in my hands and the tabs broke off just by looking at them. Not a big deal. The new module has all-new plastic with tabs, so it snapped in tight.

In the grand scheme of things it's not a disaster; the dash bezel actually does a fair job of holding the controls in the dash, but they'll just feel a little loose. It would drive me nuts so personally I try to be super careful with the tabs - and regardless of care, they often still break.

Richard

 

[1998_K1500_Sub]

I've seen multiple blower resistors where the resistor coils were fine--the thermal limiter had popped; and that results in no blower except on high speed.

No doubt thermal limiters are available from Digi-Key, Mouser, and similar electronics stores. I wouldn't know what specs to ask for, though.

Just for the record...

I had one of the thermal fuses cause a blower fan issue on my 1995 S10 recently (picture of its resistor assembly attached).

It uses three (3) of those thermal limiting fuses. Visibly / physically, they appear akin to a low-amperage diode or small-wattage resister. In fact, when I first saw them I didn't recognize them / know their purpose.

These thermal fuses should measure ~0 ohm when they're "good".

On my S10, all three were rated at 152degC (look for the marking "Tf" on the barrel of the device for its temp spec, i.e., Tf 152C). There may also be an amperage rating on them, but I didn't note it.

On the S10, the blower motor's operation depends on which fuse(s) are good. Any of the "speeds" other than "high" might be impaired or remain operational, it depends on which of the three fuses remain functional.

Here are some available on eBay as of now.

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[workingonit]

I just joined this forum, after I was searching the web for answers to my problem (as outlined on another forum I've been on for years A/C blower resistor now fails every four years, like clockwork). My wife's '98 GMC has a blower problem that I can't seem to fix, and I'm about ready to try and run a bypass directly to the blower, just so it'll work (I'm thinking of a variable potentiometer-controlled DC motor controller PWM DC Motor Speed Controller, Brush Motor Driver Controls Module DC 9V-60V 12V 24V 36V 48V 60V Motor Pulse Width Modulator Regulator 20A).

I didn't know of this website, but I'm glad to be here. Sorry to revive an old thread, though.

Like the OP, I've replaced and/or tested all the components that blow air thru the vents: one blower motor, two resistors, and one control panel, and have the same recurring problem everytime I run the heater or A/C...the blower will either quit blowing, or decrease in volume/speed randomly, then I'll have to turn the A/C off (it's usually happening on very hot days, so a decrease in fan volume/speed is instantly noticeable) and back on, or hit the control panel with my fist, to get it back to normal...or not. Sometimes it just quits, then resumes 15 miles down the road, on its' own.

I'm tired of not being able to fix this problem after so many years, and no longer can easily work under the dash, at 73 with bad back & knees, so could anyone tell me which wires to tap into, without shorting the control panel?

I'm not so electrically-inclined, but I've wired up my old '66 Chevelle drag car (now gone) and wired-up many trailer brake controllers & electric radiator fans (including my latest project, a speed controller for my '01 BMW X5 project car Done! Electric fan speed control...I'm not an electrician in any way, shape, or form), so I'm ready to bypass the panel if possible, just to see if it'll work.

 

[east302]

I couldn’t help with bypassing it, but here are two things that may be worth checking:

1. Is the connector that plugs into the blower switch at the panel melted or damaged? With the blower on, move the connector around to see if the blower stops. It could be a loose or bent female terminal (or whatever they’re called) in the connector.

2. The blower ground wire connection is attached directly to the blower housing. With the blower on, move it around and see if it’s loose.

Your symptoms mimic those that I saw when the connector was melted in my 98.