heater fan lost power.

Topic: heater fan lost power. (Read 7434 times) previous topic - next topic

heater fan lost power.

Reply #15 – February 05, 2014, 08:36:35 PM

An in-range failure is defined as any failure which does not overcome it's safeties or exceed fault tolerances by a sufficient margin to set an alert. The thermal limiter is a slow reacting fuse meant to open based on the temperature of the conductor within (not without as blower airflow addresses this). The coils are cooled by blower discharge, but the thermal limiter is almost completely unaffected by air-cooling. The conductor within varies in temperature based on the amount of current being drawn though it. A thermal limiter will be labeled with a temperature and an amperage, that amperage will typically be 75% of the fuse at the head of the circuit, in this case 30A. Go ahead an put an ammeter on a blower motor, run it at any speed you want because you won't be anywhere near the fused current, not at full-speed, half-speed, or even during initial blower kick. If you begin drawing too much current, as you would on an older car when the brushes wear out, or the bushings begin to bind or the field coils begin to drag, you'll do so for long lengths of time because unless it's noisy, you won't have any idea something is wrong. This won't bother the fuse because it is set to open purely based on current. The thermal limiter on the other hand is a fuse that opens based on heat created as current is drawn through it. The thermal limiter is expected to open between 20 and 25 amps on this resistor block, when that current is exceeded for an amount of time sufficient to cause a given amount of heat. The 30A fuse will blow quickly to protect the wiring, usually from a short. The thermal limiter opens to protect from component damage (like a melted blower switch) related to an in-range failure (although vehicles like E-vans and older Focus will melt them down anyway). That blower is junk, and until it's replaced, he'll be feeding it resistors one after another. This is what I do for a living, and I've been at it as a specialist for 15 years.

heater fan lost power.

Reply #16 – February 05, 2014, 09:59:28 PM

Quote from: V8Demon;428407

Hmm. Never seen that before. Is there a thread on it? Would be interesting to read up on.

yeah, wanted to find it, seems i didnt save it. it was sometime in line of aug 2012 when someone,, i think it may have been quietleaf who posted pics of the connector being burned up ,, you know where it plugs into the manual controls.

oh, wait,, ok,,
yeah there are three threads on it in my diy link ,,,, but the thread that shows the burnt connector i could not find,,,, that diagram i posted is the end result of such an investigation... look at the date / rev number on the top.
it was tricky but ,,, speakign to haystack ,, sure hope he gets his heat back!!!!!!!

heater fan lost power.

Reply #17 – February 05, 2014, 10:10:36 PM

Quote from: TheFoeYouKnow;428434

An in-range failure is defined as any failure which does not overcome it's safeties or exceed fault tolerances by a sufficient margin to set an alert. The thermal limiter is a slow reacting fuse meant to open based on the temperature of the conductor within (not without as blower airflow addresses this). .

partially agree,, but,,,,,, i do side with softtouch because of two words

"use" & "application"

In this case, he proves his point or should i say all of have or will one day ,,, when the blower motor barely turns at all on low speed because of garbage attached to the squirril cage.. the wire wound resistors get hotter than normal... and well.. its all down hill from there.

in this case again,, its the application. the application is a design the depends on a certain cfm of air movement to keep up with an engineered ambient temperature within the box.

heater fan lost power.

Reply #18 – February 05, 2014, 10:19:28 PM

Quote from: TheFoeYouKnow;428434

This is what I do for a living, and I've been at it as a specialist for 15 years.

welp,, umm,, hes been doing it so long some of the stuff hes done comes on the history channel :)
for instance,, softtouch can "look" at a punch card and tell you what it says.

heater fan lost power.

Reply #19 – February 05, 2014, 10:32:29 PM

Running on any of the resitively controlled speeds would increase load, technically it should use the least power on full. I actually have quite a bit of experiances with electrical curcuits, amp loads, and electronics in general.

I havent actually looked into it yet, but ill get around to it tomorrow.

heater fan lost power.

Reply #20 – February 05, 2014, 10:38:14 PM

I'm telling you, that blower is pulling too hard. I've seen it, I've had it, and I've dealt with it more times in 15 years than I can count on one hand. I'm not telling you about theories and concepts, I'm telling you what I've seen and done.

heater fan lost power.

Reply #21 – February 05, 2014, 10:46:11 PM

no doubt,, either way sumthins broke shiznit.. lol.

heater fan lost power.

Reply #22 – February 05, 2014, 11:42:25 PM

Yeah, I agree. But that doesnt mean the motor broke. I feel that.generally most of the electrical in these cars is way under built.

heater fan lost power.

Reply #23 – February 06, 2014, 12:24:27 AM

The motor probably DOESN'T seem broke, but it's drawing too much current, and can you say for sure it's spinning as fast as a good blower motor? It probably isn't, but these changes don't happen abruptly. If you put a frog in a pot of hot water he jumps out, but if you put it in cold water and raise the temp, he doesn't notice he's being cooked to death.

heater fan lost power.

Reply #24 – February 06, 2014, 01:29:04 AM

Yes, but this isnt a frog. Its a 27 year old $500 car. And it IS fused. I am very familiar with electric motors, wiring and even efficiencies of old worn out brushed motors. If it last another week or two and i dont have to pull the dash ill be happy. If it blows the 30 amp fuse, then i know i have a problem.

heater fan lost power.

Reply #25 – February 06, 2014, 09:58:34 AM

Quote from: Haystack;428443

Running on any of the resitively controlled speeds would increase load, technically it should use the least power on full. I actually have quite a bit of experiances with electrical curcuits, amp loads, and electronics in general.

I havent actually looked into it yet, but ill get around to it tomorrow.

REALLY so explain to me why High speed in just about every blower system on the planet has a dedicated power feed that does not run through the switch????????????????????????????????? BECAUSE ON HIGH SPEED IT DRAWS THE MOST CURRENT. LOOK AT THE PRINT STACKS! HELLO!!!!!!!!!!!

heater fan lost power.

Reply #26 – February 06, 2014, 10:04:45 AM

The thermal limiter is OPEN and that is why it only runs on high.( NO GROUND THROUGH THE LIMITER MOTOR DOES NOT RUN ON REDUCED SPEEDS) Follow the ground path. You can really get fancy and cut out the thermal limiter and install a fuse or jump it ouit. Normally if the blower motor starts to draw more current (AGE BUILD UP OF shiznit ON THE SQUIRREL CAGE THE LIMITER CAN BLOW I GUESS But ford has had issues with those limiters as well as GM . They just go open plain and simple. This can be easily checked with an AMMETER FOR CURRENT DRAW IF YOU LIKE !! Check current draw on the motor with an AMMETER running the motor at high speed. Should be under 20A or so!! Remember the motor draws maximum current at full speed!!! Replace the relay assembly and call it a DAY!!! Actually i think some of those are DIODES. Been a while!! NOT 100% I know some on chevys are!!

heater fan lost power.

Reply #27 – February 06, 2014, 08:19:25 PM

no relays in this circuit major tom :)

and he said on the first go at this thread that the motor does not work at all,, not even high. double check post 1

heater fan lost power.

Reply #28 – February 06, 2014, 08:32:13 PM

here are those links to blower motor stuff,, still cant find that one thread where someone posted a pic of a burned elec connector of the manual heater slector switch.

Blower motor relay modification to take heat off the selector switch and the speed control switch.
*be sure to read post 24 about our factory switches ~thanks tom renzon~!!
http://www.foxtbirdcougarforums.com/showthread.php?17041-fan-blower-location

Blower motor troubleshooting Blower has HIGH speed only and wiring diagram
http://www.foxtbirdcougarforums.com/showthread.php?19544-88-tc-fan-control-works-on-high-only&p=220320#post220320

Blower motor troubleshooting and wiring diagram
http://www.foxtbirdcougarforums.com/showthread.php?17041-fan-blower-location

heater fan lost power.

Reply #29 – February 07, 2014, 07:10:05 AM

Jay 29 Posts on a blower motor that only had high speed and now does not run. If he can not figure this out well what can i say. You and others have covered this many times in excess. First off i was posting on the HIGH ONLY portion of the issue and second hot feeding the motor would have cleared this up in two seconds, hay here is a wake up call his relay went out first then a motor or wiring issue captain!!! But when someone comes on and spouts of as being an expert and posts that a motor that runs at a slower speed draws more current how do you answer such NONSENSE, Thanks JAY Have a good day!!

Note some of the replacement speed relays or variable resistors were coming through with limiters on the entire ground circuit. Not sure if it was Ford or GM. Just a talking point