Fried plug at fan blower switch? What causes it? "REP"

[ifixedit]

Hello all,

 

This little discovery I made last night is all part of an ongoing saga concerning a "reduced power mode" condition I've been chasing on my 03 HD1500 for the past several months and I will follow up on that thread when I determine if I have once and for all found the culprit of this very annoying and difficult to pin down problem, but it's looking like I may finally have.

 

What I'm wondering is can anyone tell me what would cause both the brown and purple wires on the plug that connects to the fan blower switch to get hot enough to burn the plastic on the plug? I replaced the switch and fan speed rheostat a few winters ago because the rheostat had went out first, then the switch followed a few months later. At the time the plug and wires were perfect and all has seemed to work fine since, but somewhere along the line after the replacement things obviously got a bit too warm and I discovered this last night after doing some reading that the "reduced power mode" code P1516 could indeed be induced by either the body harness to gauge cluster connection supposedly from water intrusion (but I found no evidence there), but the plug at the fan switch sure had something out of the norm going on. Interestingly the truck has conked out a few times right when I move the fan switch to a different position and at the time I thought, nah, just coincidence, but not now. I'm also wondering if I should now replace the rheostat again as well and inspect it's connection for a burned plug or wires.

 

HMMMMMMM........... very interesting.

[00Silverado4x4]

I would also double check that you have the correctly rated fuse for the fan as well. If you have too high rated of a fuse, it will allow too many amps to be pulled through the circuit and start cooking anything in it's path. Or, you could have a shorted or a corroded circuit causing a build up of power and melting stuff. Just a thought.

[gmtech4]

A failed fan control and overheated connector is very common ,

 

It has NOTHING to do with throttle DTC

[ifixedit]

Thanks for the reply, I've never had to replace any fuses, every fuse in the truck are the ones that came with it off the new truck lot, and to my knowledge are all of the correct amperage but I will check just to be sure. I'm assuming there's enough resistance or a short going on somewhere, the question is where? Could it just be I didn't use dielectric grease on the connections when I replaced the parts and they over time can get less than 100% contact and this heats the connection up? Maybe the fan is getting bad or is turning hard and taking more power to do so as well but you would think that would throw a fuse?

 

Also interesting, but about the time I replaced the rheostat and the fan switch is about the same time the truck started it's "reduced power mode" antics now that I think about it, so perhaps there's been a problem with the fan / rheostat all along and over the past several months has just gotten worse.

 

A little research on the net has revealed several pictures of burned up wires and plugs either at the fan switch end of the plug or at the rheostat end, so evidently this is a fairly common problem, will have to do a bit more reading.

 

Anyone else that can add more here by all means feel free to throw any and all ideas my way, as all are greatly appreciated! I want to fix this problem once and for all and be able to confidently drive back and forth to work without being forced to dodge off to the side of the road because the drive by wire stopped working which never fails usually happens in some VERY inconvenient and dangerous places.

[ifixedit]

A failed fan control and overheated connector is very common ,

 

It has NOTHING to do with throttle DTC

Trust me, it may have noting to do with the DTC, but in my case I am now almost 100% certain at this point it does affect the DTC, read on and I'll explain. I have read countless threads on the internet of countless more individuals having this "reduced power mode" problem, spending thousands at the dealership (supposedly with the experts) all to no avail, and I've also NEVER seen a definitive "this is what fixes it" answer anywhere (for crying out loud even GM is clueless on this one if you check!), but sure are lots of people tossing lots of parts at the problem going on. I have chased every bulletin, redone and even re-located to the frame all grounds in question including re-grounding the PCM, 3 new throttle bodies in 8 months, new intake gaskets, flushed and changed the coolant, checked the gas cap, new knock sensors, new TAC (throttle actuator control module), new replacement harness to the throttle body, performed countless voltage drop tests (all checked out good), investigated for rodents chewing wires in the power box under the hood, dielectric greased every plug imaginable under the hood til 'the cows came home, new battery, new alternator, new O2 sensors, the list goes on and on. And always the same and only code P1516 (TAC malfunction), and never ever any other codes which has been happening on a daily basis again for the past few weeks. I've spent more time under the hood on the damn thing in the past 2 months than I've spent sleeping or talking with the good wife. I'm to the point I've nearly taken the radiator cap off and driven a new truck under it.

 

Just by chance yesterday once again researching and finding the same old "I don't know, I tried this and that" answers everywhere on the net, I came across a site where the technician said to ALSO check for signs of water intrusion under the dash, near the A pillar, etc., and to look at the body harness to gauge cluster connection for signs or corrosion or debris as he stated there have been reports of water intrusion and he stated with utmost certainty this most definitely COULD cause issues with the DTC because of it's sensitivity due to shorting or variables in voltage that could interfere with it's operation. My thinking is if you have funny stuff going on in the electrical system of these complicated everything electronic vehicles, it could surely have an effect on the DTC. I've also read of guys installing plow winch controls, electric brake controls and so on and all of a sudden the truck doesn't want to run right throwing codes left and right, a guy I work with had his happen on his 06 HD. From there the technician stated there could be a short or other issue somewhere else under the dash, like at one of the other controls, fan switch, etc. Sure enough, I take mine apart and the damn fan connector is all burned up.

 

Again, the truck has went into reduced power mode just by changing the fan speed a couple of times on me now when using the heat or the A/C, in any case it always happens when I'm using either which is getting to be a bit too odd to ignore. The other day I switched the fan from #4 to #3 while driving along at 60 and the truck immediately went into reduced power mode like I threw a kill switch for the engine. Once again happening with perfect timing not to just say it's coincidence and making me think perhaps this is my problem. Finding a fried plug along with the info I read yesterday and my seemingly most times I touch the fan switch and it kills the truck sure seems enough evidence to bolster my theory wouldn't you say?

 

Since removing the plug from the fan switch (and cutting it off) last night, I have immediately noticed this morning that the gas pedal acts completely different (like it used to and is supposed to). Prior to this discovery and for the past several months the pedal was weird, I could barely touch the gas and could cruise at 65 MPH, but in town just barely touching it and trying to hold it steady to make it only go 30 was impossible unless I continually let off on the gas, it would not go 30 without doing this period, this morning it suddenly now goes 30 holding the pedal steady without a problem. The throttle was ramping up too fast just by moving it a hair, it had an abrupt jump and would go from idle to 1500 RPM just like that which seemed odd to me, there was no gradual increase in it's speed like you would have with a carbureted engine, now the gradual increase is back like it should be. It's as if before the range of the accelerator was out of sync or calibration.

 

So I don't know, you tell me?

[00Silverado4x4]

Sounds like you need a really good schematic and start tracing both circuits from the battery to the components in question and replace whatever is melted, shorted, broken, bent, busted or otherwise.

[ifixedit]

I'm wondering if perhaps the parts guy gave me the wrong rheostat that one cold winter day or if those lousy fan switches are prone to shorting out inside causing the wires to heat up, or maybe I just neglecting to use dielectric grease at the plugs when I replaced things was maybe the mistake. We do go through some rough winters here with lots of variables in moisture, your shoes constantly dragging the wet, sloppy salty crap into the vehicle, the carpet gets wet in places, then it's froze and thaws out, it goes from -20 sitting at night to warming up +60 when you drive. Probably a wonder more things like this don't act up.

[gmtech4]

i tried to tell ya but if ya dont want to listen to a 14 yr GM tech ,then dont ,,,

 

good luck ,,

[ifixedit]

i tried to tell ya but if ya dont want to listen to a 14 yr GM tech ,then dont ,,,

 

good luck ,,

Here's a few YaYa's back at you. Interesting, but as with most other replies I've seen, most opinions are very short and say "that has nothing to do with it," but no answers either, seems to be a trend. If you think you know what's wrong then take a chance and just say so unless you're worried about being wrong. Not trying to get into a pi**ing match here but if you keep an open mind and read my post above and what I've already done along with some very strong clues to back up my suspicions, what might you suggest I do next? I've also read of several other people saying their truck goes into reduced power mode when using the heat or A/C. Just conicidence? I like many others with this issue have thrown everything including the kitchen sink at the thing and like many countless posts I've read over the past 9 months NOBODY has a conclusive answer including many techs and GM. I've gotten sick of reading story after story of people taking their vehicle to the dealership, they flash the computer, throw parts a it, fix the grounds, replace the wiring harnesses, try this and that, say a prayer over the truck with a priest present, and then say it's fixed only to have it happen the next day (or worse, a block down the road) and their trucks keeps doing the same thing and come back to the dealership over and over until the customer has spent 2 grand and are then told," sorry, we have tried everything and we have no idea at this point what's wrong and don't want to talk to you or see you here anymore." Search "reduced power mode" and your computer will be overwhelmed with stories on the problem ranging from owners of Silverados, to Impalas, to Yukons, to Saturns, but zero answers to the problem other than we will keep throwing parts at it until the parts bin is empty.

 

Just in case anyone here is having the same problem and is actually interested in solving it, I removed the fan switch from the head unit tonight, the thing is only 2 years old and was completely cooked and fell apart in my hands in two pieces, the plastic front part that the shaft goes through was gone, nothing left! The switch was completely fried and was clearly shorting not only against the contacts inside the switch but the wires connected to it as well! What's even more interesting is the switch even in the terrible condition it was in stil operated the fan likely going from fine one minute to bad the next, so even for the most keen of people to identify possible problems would never realize this could be the actual problem as it would likely go undetected.

 

As to your point of being a tech: I've got a friend that has also been a (non GM) tech for a very long time and admits they have had GM trucks come in with something as seeminly simple as a trailer brake or snowplow install and afterwards have been stumped with this issue of reduced power or other issues with the truck just refusing to run right, stalling, codes thrown and so on. So I don't buy for a minute anything supposedly outside of the drive by wire has zero to do with it as when the PCM picks up a problem it's likely to throw the truck in safe mode until the problem is corrected.

 

14 years as a GM tech is great and you've probably solved many a problem so don't take any of this the wrong way, all the pistons and rods under your avatar to me mean nothing though. 14 years doesn't automatically give you a certificate that you've got it all figured out and know and have seen everything, you still may be able to pick up a few pointers here and there. Us 'Joe Blow' backyard mechanics that have been working on cars and trucks (me personally 40+ years) have learned a few things over the years as well. But even after all these years probably the most important thing I've learned is I always keep an OPEN MIND that there is still more to learn and I DON'T rule out anything untill i vet it one way or another because I just might learn something new.

 

Someone over the next few days is going to be eating a little crow I would bet.

[gmtech4]

you have a great day ,,,,no crow eating here ,,,ill try to keep an open mind sir

[intheburbs]

Sorry if I seem like an ass for pointing this out, but it's a resistor pack for the blower, not a rheostat. It's a circuit board with some resistors on it, as opposed to a variable resistor. Typical failure mode is that you lose fan speed 1 and maybe 2.

 

It's a common/known problem on these trucks, and the dealers always have a few in stock, so no, you did not get the wrong one or a bad one. I had to replace the pack on my '01 Burb.

 

With that exhaustive list of parts you've replaced, did I miss where you've replaced the BCM or the PCM? Sounds like it might be a computer issue, with two disparate circuits interfering with each other.

[bbwb]

Out of curiosity, when you replace the switch/connector/wire, does the problem go away for a while until it cooks again?

Also, (I may be wrong here) but doesn't the wiring harness have a plug connector at the firewall (plug between the interior and exterior harness)? I wonder if you have a bad pin connection at this connector.

bbwb

[ifixedit]

Just a follow up this morning. First off in case I've caused any confusion or angst here (sorry for that) I'm not trying to contend that the drive by wire has any effect whatsoever on the fan switch, it's longevity, if it causes it to burn out ect., etc., claiming that would be completely stupid. I was simply trying to find out what causes the switch to fry like it did and at the same time I seem to have discovered the answer to my reduced power mode problem that has been going on for months now.

 

What I am saying is I think the burned out fan switch / fried plug and resulting shorting is what was actually the culprit causing the truck to go into reduced power mode. And, if you've been having the reduced power mode problem as well, have tried all the things I have and you are still having the problem, I would advise that you check your fan switch.

 

I have looked for a main plug at the firewall under the dash, haven't found anything as of yet but I did trace the wires from the fan switch back the rheostat (or whatever we want to call it) and the wires / connections at that end are all good, no signs of anything getting hot. So I assume the switch itself is a cheap piece of plastic junk which it sure appeared to be when I bought it, seeing what's now left of it confirms that.

 

BTW: Day 2, truck continues to run perfect.

[ifixedit]

Out of curiosity, when you replace the switch/connector/wire, does the problem go away for a while until it cooks again?

Also, (I may be wrong here) but doesn't the wiring harness have a plug connector at the firewall (plug between the interior and exterior harness)? I wonder if you have a bad pin connection at this connector.

bbwb

Sorry I didn't answer your question right away. I had no idea the switch was bad in the first place so didn't know to look or replace it to see if the problem would go away. All I know is it started doing it mostly last winter of course when that switch gets used a lot, the truck started going into reduced power mode just once in awhile, but over time (and after many attempts with repairs in other areas) has gotten worse and worse. As I mentioned above, just to test for now, the switch has been removed, the end of the plug is for now cut off (I got wires dangling out of the dash ), and I'm going to drive it that way for a few days. So far it runs and drives waaaay better than it has in a long time AND no reduced power mode.

 

Interesting but I also noticed the other night (before I found the bad fan switch) under hard acceleration the headlights suddenly dimmed and the truck stumbled and lost a considerable amount of power momentarily, then it was like someone hit the nitrous switch, the lights went back up to normal and it picked right back up (never done that before) telling me there was suddenly a considerable electrial load or interruption to something put on the system (like from a shorted out fan switch?).

 

@ intheburbs The thing I bought 2 years ago that needed to be replaced for controlling the fan speed (yes, correctly called a resistor, parts guy called it a rheostat) looks similar to what's pictured in the link below, no circuit boards on it that I recall. It is located on the passenger side on the bottom of the air duct box. Yes, I've replaced a ton of parts already, no more for now as all it has been is a guessing game as of late. I've not replaced the PCM, just re-grounded it, but virtually everything else concerning the drive by wire (gee, I miss throttle cables!) is new.

 

As I mention above, on day 2 and the truck is running / driving awesome so far.

 

http://www.monsterautoparts.com/CHEVROLET/s10/_s10_images/S10%20Truck%20Sonoma%20Blazer%20Blower%20Motor%20Resistor.jpg

[w3jn]

If the plug is burnt, it's either arcing and not making a good connection, or there's too much current draw, or both. Arcing, especially with the considerable amount of current the fan draws, could certainly cause electrical noise in the harness that is being picked up by the PCM and/or BCM (they DO talk to each other) and confusing either or both, causing this problem. An easy way to see if the thing is arcing is to turn your radio to AM, open the hood, and tune to a unused AM frequency. Turn the fan on and off and you should be able to hear the difference in noise in the radio.

 

Were I you I'd measure the current draw on the fan to see if it's in spec. Easy to do, pull the fuse, put in a fried fuse, and connect your ammeter at the little exposed tabs at the top of the fuse. If it's drawing too much current I'm betting some meeces got in there and made a home - or the bearing is shot (every Chevy I've ever owned has eventually eaten its heater fan bearings).

 

Good luck, it looks like you're on the right track!