No Scope Required? (GM Blower stuck on HIGH!)
Vložit
- čas přidán 5. 03. 2021
- This 2005 Chevy Tahoe decided to turn it's blower motor on HIGH SPEED, and it refuses to shut off!
The owner had to disconnect the battery, and wants it fixed.
This automatic HVAC system features a smart "Blower Motor Controller".
Do we NEED a scope to diagnose this problem?
Enjoy!
Ivan - Auta a dopravní prostředky
Scotty Kilmer told me that back in the olden days, the blower motor wheels were spun by hamsters! (read next sentence in a high-pitched voice) And all you had to do was replace the worn out hamsters; no fancy computers or fancy tools needed!
I think PETA put a stop to that. It would be cruel to make Hamsters do the work on GM.
I upgrade to a squirrel 🐿 for higher efficiency. Until I replace the resistor pack
Catching me without a scope is like catching Scannerdanner without a scanner. Even at the grocery store I have my scope to analyze my shopping list. now thats called deddication, lol.
hahaha xD
Ivan thanks for taking us along on this one. Hope all is well with you and miss the flying videos 😆!!
I didn't watch this video for a while cause I misread the title thinking it said the blower only works on high and you would just replace the blower resistor. Now I re-read it closely and realized that this will be way more interesting lol.
Thank you Ivan. Good job again. Have a blessed and safe week to you and your family.
I don't have a scope, but I am into my rc planes, so i would have grabbed a spare servo and used that to try and confirm change in pwm value. In theory the servo would have moved in relation to the pwm value. Not sure if it would have worked, but I would give it a try! 😁 The servo is operated by 5v, so i would have grabbed 5v from a usb adaptor plugged into the cigar lighter, then simply tapped the servo signal wire onto the pwm circuit I wanted to check. The RC aircraft geeks way of checking it!
I hear what you're saying when you want to diagnose problems more simply, without the scope. As long as that technique doesn't interfere with understanding, there's no problem. But I find that when exploring an unfamiliar system, one of the biggest challenges is to learn how these devices talk to each other. For that, as you nicely showed, using the scope makes interpretation so much easier. It is disappointing to see another example of new technology making cars less durable. In the old days when a blower resistor overheated, the owner with more brains than money could just accept an all or none blower fan. Failing in a way that demands urgent professional help is poor engineering.
Great comment! Yes, this failure mode is quite inconvenient :)
Great job Ivan. Nice easy diag and repair.
Thanks Ivan for the diag and a couple different ways to make sure the right part was changed! Could help if on a trip with limited tools but most would have a multi meter with them. At least a do.
Muli meter and an incandescent test light (as opposed to LED).... never leave home with out them!
Nice quick diag. My brother’s equinox is having problem with blower motor or air problems. It doesn’t blow or barely blow on high setting. BUT it an intermittent 🥲. I checked all wiring,amp draw, resistor ,hvac module. All checked out good. Found cabin filter is covered with debris/leaf. It’s nasty. Changed it. It blow nicely. He haven’t text me since then. I hate intermittent problems.
To me the most important thing was that wiring diagram.
Nice one Ivan great content as always ...
Ivan glad to see you are almost at 100K subscribers not sure what kind of special you will have but I am sure it will be BIG
Great idea...100k special!!
Great video Ivan! Looking forward to all the upcoming content!😁
Thanks Greg! Got some bigger case studies lined up, just takes longer to upload :)
@@PineHollowAutoDiagnostics I’ll be waiting on that notification on my phone! 😉
You should have tried AC on the DVM. Here's what the manual says about my 80s Fluke 8060A:
"Most meters in use today have average-responding ac converters rather than true rms ac converters like the 8060A. Usually the gain in average responding meters is adjusted so that the reading gives the rms value, provided the input signal is a harmonic-free sinusoid. However, if the signal is not sinusoidal, the average-responding meter does not give correct rms readings.
The 8060A ac converter actually calculates the rms value through analog computation. This means that 8060A readings are accurate rms values not only for harmonic-free sinusoids, but also for mixed frequencies, modulated signals, square waves, saw tooths, 10%-duty-cycle rectangular pulses, etc."
I guess GM really screwed up. Probably next time they can install the controller on the top of the HVAC unit so you have to pull the dash.
They need to make it like Liebherr material handlers that have the controller built into the blower motor that is mounted under the operators seat. $360 for the new motor and about 4 hours to replace it. Great fun!
You should try changing one of the actuators! Had to practically stand on my head to change one, and when I was done, the blend door worked backward. I just left it that way.
Always doing great job.
Thanks for the video Ivan.
Thanks as always, Ivan!
Ivan, AWESOME good information as always hope in the future u will have some communication and programing case study as always enjoyable brother thanks.
That was an excellent description of PWM and how a scope is so much more accurate. but yes, us DIY guys can't justify scopes, unless it's the Uscope. That dude is pretty cool. Thanks again Ivan.
Thanks for the comment, Wyatt! Hope all is well!
I never thought about depinning the connector on these.. Thank you Ivan! Luckily these trucks have a nice hush cover because the aftermarket connector is a mess 😁
The DMM you have has ability to measure % of the modulated signal you should use that instead of measuring the voltage. It is the duty cycle that changes from the HVAC controller.
It was nice to see the Standard motor products replacement was made in USA.
Well done. Thanks Ivan!
Ivan, you're the king of ingenuity. Let's get that module open, how about a heat gun, and a couple of small putty knives?
Good information here for people like me, who may not want to invest in a scope. If I were troubleshooting this, I would have changed the wrong controller. The readout looked wonky and would have fooled me.
There is not much to that controller. Usually just some type of power transistor that is in series with the motor and ground. The 12v power is passed though to the one side of the motor. With a turn on signal (in this case a low voltage), the transistor connects the other side of the motor to ground. They usually fail short circuit and blower runs continuously. Thanks for the video Ivan!!
Great video!
Another awesome video Ivan! I hope we dont ever lose you tube, there goes my entertainment! Just saying...
Hi Roxanne, glad you are here!
@@PineHollowAutoDiagnostics my 2004 Jeep Grand Cherokee overlond is rpm going up and down n i try to fix it it still doing it n i put new parts on it to
Great advice to get the schematic first! It'd be really cool to see a video showing all the different resources you wind up using to find schematics.
Thanks for busting out the scope and showing us how the input signal worked. For no-scope diag, there's a lot of comments about what meter setting would be best for testing with module powered up. I'd be curious to see what diode test &/or resistance looked like between power in and blower + on the module with it unplugged. A forward diode drop voltage or dead short? "Well there's your problem..."
Great diag Ivan. I had a terrain that they change blower motor and resistor. turn out to be the audio and hvac control unit.
Yup, better test then guess! :)
👏👏👏 Nice video. Thanks for sharing.
Alternate Fix : Advertise For Sale on Craigslist : SIBERIA ! They will NEVER notice ! Nice diagnosis .
Lol ivan, I'm sure everyone knows that blower resistors always go bad on GMs. Lol. I've replaced them many vehicles lol. It's a curse on them trucks, hehe. You went all out testing them to be sure! Pretty cool video!! 😎 thumbs up!!
For several years now, I've noticed more and more that scope use is taking over diagnostic duties. Bernie Thompson uses a scope a LOT!
It's the only way to see what the computer is doing :)
Saturday morning coffee and a PHAD video. Great teaching video. My personal HHR turn signal switch took a dump. Wire diagram VTOM confirmed my suspicion. New AC part to fix. Although Ivan know my luck with NEW GM PARTS. BTW THANKS IVAN by the new pressure and vacuum tool. Can't wait to use it.
Always looking forward to his next adventure... It's hard NOT to!
haha Bill yes I know your luck! Have fun with the PHAD Transducer!
Had this same issue on a trailblazer.key out and blower motor on high. Owner drove over with the fuse pulled. Used the scope to confirm that the controls changed the duty cylce.blower motor resistor was replaced.done n done 👍
Great reminders!!
I know not all meters have the feature, but I noticed your clamp meter does have frequency measurement. I work in the rail industry, and our air brake command is generally PWM. I tend to use the frequency measurement in a pinch which is good for these kind of cases where you only want to verify the pulsing.
My 04 Yukon did the same thing today, glad I came across your channel, and great tip on de pining the new wires are putting the old ones in the new pig tail, did you have to use that foam spacer in that kit ?
So, when did a little glue keep you out of something. Getting spoiled.
I was about too asked Ivan and then I saw you asking him....What a let down huh.....lol
Not a NPR fix this time. Almost feel cheated.....
The part is about $50. If it took him more than a half hour to open it up to attempt a fix he's already behind...and he might not have been able to fix it. Time=money!
@@miken8150 That one went right over your head didn't it?
@@miken8150 Admit it, Ivan loves the sound of that Parts Cannon going boom :)
Great video! Would a test light be better than a volt meter to test that circuit?
I like when you use the Snap on scanner. Do you still the the 2500 Brick ?? Or VAntage ? Love the show !!!!!!!!!!
Ivan, thanks a LOT for showing a diag with only a multimeter (and alltell/mitchell/whatever for the diagram)! Those of us DIY guys who can't afford a scope or pro scanner only have what's affordable and this shows that it's definitely possible for us down here in the DIY trenches. Also, I DO NOT believe you're not gonna take that controller apart because you're just as curious as we are to see the real cause of this issue and what might be possible to even fix the root cause rather than fire the parts cannon once again. Glue won't stop you, will it?!!! I'd be hittin' it with my hot air gun first to see if that would loosen it up a bit first before going into destructo mode. ;-) One vote for taking it apart just to see what's inside. :)
You don't really need a wiring diagram for these things. The two fat wires are power and ground. The skinny one is control ;)
Matt T Thanks!👍🔧
Ivan thanks
I've learned the hard way that is is best to qualify the heater blower current on high with the engine running since alternator output will increase the supply voltage and therefore the current. It has also been my experience that current flow should not exceed 50% of the fuse rating which in this case would be 20amps since it utilizes a 40amp fuse. I have also seen a few motors that start out good or less than 50% and then begin to increase as it heats up so I tend to let it run for several minutes to catch this. Good video. Oh and I believe the Snapon Verus scope should have graphed that duty cycle just fine. May have to use the autofind feature to adjust the trigger level but it should work at that frequency. Thanks for the video.
hmm what is the "autofind" feature?
@@PineHollowAutoDiagnostics It's easier if I make a short video and send you a link. Give me a bit and I will show you what I mean.
The belabors the troubleshooting so much it helps understand why labor rates are so high.
had that happen on my 93 cad only 16,000 miles on it...it was the fan control,,,easy to get to..
Another method would be to disconnect the control line (pop the pin out of the connector). The fan should not spin without a control signal. Admittedly this is an assumption, but at least it would make you more confident on the diagnosis if you don't have a scope.
Only if you know how the circuit works beforehand :)
👍 Privet iz Canadi!
I've had that same problem on my 05 Suburban it turned out to be that blower controller module on the heater box on the passenger side
It’s almost Spring and Ivan’s up and loading early ‘cause it’s light out and the horses are hungry. 👏😉🔧
All good stuff.
Good video there is your like 👍
The blower was stuck on in my 01 Navigator, (only KOEO, key off/engine off). Long story short: Water was leaking in through the windshield seal and dripping on the fuse box under the dash.
Was the Navigator modified by Tetley?
Hey Ivan grate video. Q: was it her blower motor or the the car's blower motor that went bad.
I think alot of people don't check b/c they don't understand how it works. I was at a shop recently and watched them throw everything at it for a compromised wire in a previous repair.... It was entertaining to say the least.
And sad for the customer lol
Thanks for sharing Ivan. As usual a good explanation how it works and how to troubleshoot. Stay well Artie 😊
Thanks for the comment, Artie!
Before I get into the video I'm guessing the mosfet that runs the blower fan located in some form of ac control module has shorted
BTW, on some cars if the cabin filter is exceptionally clogged with debris, running the blower motor other than HIGH will cause the range/speed resistors to overheat and fail. These resistors are usually placed in the air flow of the blower. No flow, no cooling for the resistors, burn up open.
Great point!
Why not use the duty cycle/Hz setting on your multimeter? Compare that with the data stream to verify controller function.
Does my DVOM have a duty cycle function? Let me check...
Is the failure of the duty cycle graphing due to Peak Detect being on?
Ooh 😯 That’s Cool. I Didn’t know you could do that with a scope. Ok So I might have missed this, but you have to Set the Trigger where exactly in order to have the lines separate as you adjust your blower speed? & You on the Blower Signal wire and a known good ground correct? Please & Thanks
The trigger stops it from parading across and off the screen and allows you to focus on one particular pattern section 👍
I don't know, fancy pulse width modulation, the output mosfet must be very crappy :-D
A bunch of wire wound resistors not good enough for g.m lol.
Nice easy access to the pulse master box doobre :-D
Hi Ivan , thanks for your good advice , I quite enjoy seeing you diagnose and then fix the probem , I enjoy the wiring diagram process , from Tony McCarthy from bedfordshire England 👍👍👍
Thanks Tony!
I am sure you could get the controller open if you wanted to.😁
it would be nice to see the waveform whit the new blower resistor!!
Wouldn't change the signal, but the blower speed does :)
Another fine GM-sourced vendor for that part there. What a way to fail! I'd wager 95% of the population wouldn't know what to do in this instance, aside from disconnecting the battery ... and 3% wouldn't even think of that! They'd come out of wherever they go to find the battery as flat as a pancake, and be stranded. Could be life-threatening in a blizzard, or up in northern AK where it's -40°F!
I got a dealer story for ya, Ivan. So my neighbor's '17 Ram 1500 became a no-crank, no-start at 11pm at his work about 6 miles from here. I ran out there with a jump pack, since he said his battery was dead. I get there and see the light under the hood blazing away bright, along with nice bright interior lights. I threw the jump pack on anyway, and got nothing but a "Click" at the starter when cranking. I figure either the starter motor was dead, or the battery cables bad. Since we got a click, the command was there, the key switch was working, etc, etc. - all good, probably a simple fix. I tried getting under the thing to whack the starter - I couldn't barely get my fat belly under this thing, lol! The step rails are too low, so I had to go from the front. The air dam got caught on my fat belly and I got stuck, lol - he was roaring! I couldn't even reach the starter enough to give it a hard enough whack. Had to run home and grab the trailer, and haul the thing home. Since he's owned the truck barely 60 days and bought an extended warranty, he had me tow it to the dealer where he bought it from the next day. They told him on the phone, "Yeah, everything should be covered." As soon as we get there they whack him $150 for a diagnostic fee. We should've left right then. Long story short, he picks it up 24 hours later to the tune of $1,000!!! I believe this was on top of the $150 they already hit him with!! They replaced the starter, one battery cable (or maybe both, but I think it was just 1), and the battery which was only 3 years old and would've been fine with a overnight charge. He demanded to have the parts back, and they refused, saying they had already been "exchanged" or "trashed". He is LIVID. Lesson learned there. DO NOT buy an extended warranty, and steer clear of any dealers!
WOW that's CRIMINAL! A 2017?!? What a scam haha
@@PineHollowAutoDiagnostics - I hear that! I feel bad for the guy. What a mess.
Curious what that second signal was... Clearly an on and off...
Hey Ivan, what are you using for wiring diagrams these days? BBB industries seems to have restricted access to their diagrams these days.
When initially using the voltmeter wouldn't AC true RMS have been more "meaningful" than dc when the signal is a PWM?
Yes, great question. Maybe that would not have shown the "true" numbers, but it would show that the head unit was working?
Grasias
I noticed you have a Hz setting on your DVOM ... Would that be of any use if you do not have a scope handy? BTW - Great as always!
It would show a number if the signal is in fact a pwm signal. Like 40hz like Ivan implies. But that number wouldnt change with the speed control. If he have a dutycycle or pulsewidth setting on it on the other hand...
@@stevejakobsen2765 I was afraid that me be the case ... the frequency is constant, just the pulse width changing .... So all it would really tell you is that you indeed had a pulse of some kind... Thanks!
I wonder if you'd have had better luck with the meter if you'd taken it off 'auto" to the fixed voltage range. That may have sped up the meter's summing of the PWM.
Not sure what was going on with duty cycle on the Verus but I doubt it was the frequency being too low. It's in the same range as points ignition at idle. Did notice peak detect was on which may have been messing things up.
Points ignition? Probably wouldn't use "duty cycle" to measure that?
@@PineHollowAutoDiagnostics You use duty cycle, or dwell if the meter has it, to accurately set the points gap. More accurate than using a feeler gauge or matchbook.
Why would I not use a scanner first to diag the problem ? would a bidirectional scanner acomplish the same thing ? What about the fact that the scanner would show possibly a bad module and you could plot the voltage on a graph to uncover the problem ? thanks Ivan as always a 5 star video Joe
Scanner doesn't verify wiring integrity to the controller...
Ivan, why didn't you use the frequency mode on your meter to show the pwm change?
Because the frequency stays the same at 40Hz ;)
I think a good example of how to use the MM in this situation would have been to set it to FREQUENCY mode (Hertz or Hz) and show how the Pulse width changes the frequency of the signal. This would have completely confirmed your diag.
Hz is just the frequency, which would stay constant at 40Hz. Nothing to do with duty cycle or Pulse width :)
@@PineHollowAutoDiagnostics thanks for the information! That definitely helps me to understand it better!
Can we get a teardown of the old module?
What took out that part? Seems air restriction will result in overheating of anything that hangs its ass-end into the airstream, and if restriction is still there the replacement will also fail soon.
Age and Heat...
Only in a GM would you consider replacing a blower motor resistor "regular maintenance"
Did you try the Hz function on your voltmeter? Might it have shown useful info?
It would have shown 40Hz constant
What about using the duty cycle or Hz% on your multimeter. Would that give you a better reading then voltage?
The Hz range on a DMM sould not really give much indication. If you watch closely the pulses are coming at equindistant intervals. So unless the pulses stop and become a permanent HI or LO signal the DMM should read the same frequency. However the DMM may be confused enough by it being a square wave with a non 50-50 duty cycle to give you some kind of a varying reading on the Hz range.
You could even try the AC voltage mode on the DMM to make it look for some kind of changing voltage.
But sorry to say so, whatever reading you get is an indication at best.
Ask yourself; what would these methods display if there were pulses but they were not making 5V or GND.
Or in a situation where you were expecting a 0-12V pwm signal but due to some error like short to a reference voltage etc it was reduced to only a 0-5V or 5-12V pwm. Your DMM may not catch it or lead you on a wild goose chase.
There is a good reason to get a scope. And if you want to go really low budget get one of them chinese DSO kits like the DSO138 etc. Complete with acrylic case you are looking at less than 20 bucks and the sampling rate is good for up to 50kHz. That is enough to trace PWM signals and stuff. And even if it falls flat on higher frequencies and does not resolve to microseconds it will give you enough hints to prove the existance of a PWM or serial Bus Data.
@@randomsteve4288
Your answer, was very good, and complete, why scope and no DMM.
I hope, Ivan, put your comment right on the top,so the people that going to read the comments ,understand why scope,from the first comment they going to read.
Like #343
Thanks for the video!
Hey Ivan got a off topic question on the Creader launch scanners and registering and updating or what they refer to as upgrading do you know if they charge you for software updates or upgrades? And how long to they update the scan tools? Sorry to dump this one on you out of the blue but I thought if anyone knew you would.🙂👍
Usually 1 year free updates...
@@PineHollowAutoDiagnostics 🙂👍
Learn or in some instaces to use the good ord electro mechanica volt ohm meter which will many outdoes the slower reading modern DVM which are too slow to read a value.
Wouldn't you use the hertz function on the multimeter?
The Hz wouldn't change during the test, so information wouldn't be very useful...
Been there done that.. varistor.
we have a 2017 chevy trax blower motor stuck on high.. diaged it and was the blower motor resister simple right??? replaced it then after a few days it stopped working completely ... another diag... found the power and ground wire at the resister had gotten hot almost burned up the connector.... THE FIX???? the power and grd. termals. were loose, unpinned them one at a time readjusted the so the pins would fit nice and snug in the termals. i wont say it was easy but as a friend of a friend once said "LOOK NO PARTS REQUIRED".... i wonder who that was???????? anybody??
Had a friend with a 2006ish silverado that the connector for the blower motor resistor basically melted
Isn't 2017 too new to be having issues?
@@PineHollowAutoDiagnostics one would think so.. but quality control IS NOT what it used to be.. i have found other connectors with loose fitting pins on the same car, and my trk. 2017 chevy silv. 1500 crew cab short box 5.3l. i guess "THEY" were having a bad day and or week depending on how you look at it!!!! just thought id share TO MAKE SURE TO CHECK ALL CONNECTIONS FOR CLEAN AND TIGHTNESS !!! hope this helps somebody's!!!!!! oh and thanks for the reply!!!!!
👍👍
I think your test light would have been a better test, if the HVAC controller could drive it. The resistance may be too low.
👍
I don’t have a OBD reader that does pulse width or an amp clamp or enough sense to use either one? I know, like most mechanics of today, start changing parts. Quick fix, put control on outside air, leave fan off.
Resistor for fan motor
I bet that "blower motor control processor" is just a 20 amp PNP transistor on a heatsink. Closes with ground at the base. A Rapid switching solid state relay for the blower, would do the trick I think. Some engineers at these automakers are totally full of themselves lol.
A GM with wiring or electrical problems? UNHEARD OF! LOL
How does the fan still have power even with the key off.
The wiring diagram showed the 40A fuse, full time power (not key switched) and the ground is fixed. The solid state device stuck in the on position.
Change the transistor on the controler
trailblazers have that same fan controller. Same problem. Do not replace with a amazon unit or you be replacing it again in 4 months,don't ask how I know.