Last post on Nov 05, 2013 at 7:31 AM
You are in the Chevrolet Blazer
What is this discussion about?
Chevrolet, GMC Jimmy, SUV
#408 of 609 Re: 2000 Chevy blazer rear hatch [tidester]
Aug 02, 2009 (5:40 pm)
Sure. Things like a loose fuse holder. Causes an increase in contact resistance, and more heat. Fuses are blown by heat, whether caused by excess current, ambient temperature, or high resistance in the fuse holder itself. Not uncommon to see a fuse blow when a cheap inline holder is used on a high current circuit. Sometimes, if the fuse is rated high enough, the holder itself will melt before the fuse does. All fuses have a specific resistance (very low, but exact) so that when the rated current is reached, the resistance will cause a rise in temperature of the fuse element and cause it to melt. In the case of, for example, an ATC30 automotive fuse, the melting point/time varies by the current applied. At 30A, it will get warm, but maintain integrity. At 35A, the heat will rise to melting point in 10sec, 40A in 5sec, and 80A in 1/2 sec. A dead short from a high current source (ie: the battery) will melt the fuse pretty much instantly. But if you are running at 30A, and with a poor fuse holder contact, the additional rise in temperature applied to the blade of the fuse will lower the current capacity of the fuse. Also, unless otherwise specified, fuses are rated at 25 degrees C, so if you are pushing the limit of the fuse at sub-freezing temps, summer temps will most likely cause the fuse to melt.
In an auto-resetting circuit breaker such as used in a headlight circuit, the same principles apply. When the temperature of the circuit breaker reaches a pre-designed point, the circuit path opens, causing a cool down. Once it cools down, it closes the current path and will repeat the cycle until the fault is corrected.
A really neat trick is to SOLDER a low current fuse into a circuit without "blowing" the fuse. Which is why Bussmann/Cooper always advises to solder inline holders before installing the fuse.
Not so much with automotive applications, but in industrial apps a poorly mounted fuse block can open a fuse through vibration.
#409 of 609 Re: 2000 Chevy blazer rear hatch [jlflemmons]
Aug 02, 2009 (7:50 pm)
Thank you for that reply - very informative and helpful!
SUVs and Smart Shopper
#410 of 609 2002 Blazer - Ignition Swith, blown fuse, LED panel
Aug 04, 2009 (2:51 pm)
I am having a problem with my LED panel lights (Shift position indicator and odometer). When my ignition switch is in the RUN position, the shift position indicator, odometer and radio stop working. When the key is turned back to the OFF position, they all work fine. When the key is turned back to the LOCK position and pulled out, the radio is still on. Also, the 10amp "Cruise Control Module and Switch, Body Control Module, Heated Seats" fuse keeps blowing out and the temperature gauge does not appear to be working.
Is this an ignition switch problem or something worse?
Are all of these problems related or is it more than one problem?
#411 of 609 Re: 2002 Blazer - Ignition Swith, blown fuse, LED panel [steveo16]
Aug 04, 2009 (3:16 pm)
Wow, quite a list of symptoms there. How many miles are on the vehicle? Some of what you list sounds like a bad (worn) ignition switch, but I would have to look at a schematic to see why the CCM fuse is popping. There may be two issues at hand.
I have a basic schematic set on this vehicle, let me check it and get back with you.
 On the fuse issue, try turning off the cruise control switch on the stalk, and (considering it is 103 here today ) don't turn on the heated seats. Put in a fuse and see if it pops immediately. If not, turn the switch to run and check fuse. See if the indicators in the instrument cluster come on. If still good, turn on the cruise switch. Try and isolate what function is drawing the high current.
I don't have the complete schematic available, but I believe the functions in the instrument cluster that you listed as malfunctioning all come from the BCM, and the radio has aux power that (I believe) is also supplied by the BCM for the delayed power off function. The cruise control used to be a simple system, but I am thinking it also has a tie-in to the BCM.
Try the tests I listed above and tell us what you get.
#412 of 609 Re: 2002 Blazer - Ignition Swith, blown fuse, LED panel [steveo16]
Aug 05, 2009 (9:14 am)
Check the oil pressure switch on the left side of the engine first. The temp switch
and oil pressure switch are wired so that when one goes it appears that they both
go out. As far as the other problems I don't think they are related to temp guage.However, I've been wrong before. The other problems and possibly all the
symptoms may be because of the ignition switch.Have you had it checked for trouble codes? I really don't know if I can be of any help at all. Check oil pressure switch and temp switch. Borrow a code scanner or take it to a repair shop to see
what codes (if any) show up. GM did a lot of wiring changes to that body style
between 1995 and 2004 because of electrical problems. Sorry I can't help.When you get it fixed,can you tell us what the problem(s) were? I'm curious.Thanks
#413 of 609 Re: 2002 Blazer - Ignition Swith, blown fuse, LED panel [jlflemmons]
Aug 05, 2009 (2:23 pm)
Thanks. Those sound like good places to look. It doesn't have heated seats, that is just what the manual says is on the circut. Could there be loose wires for a heated seat that are shorting out?
Also, where can I find the Body Control Module and how can I test it?
#414 of 609 Re: 2002 Blazer - Ignition Swith, blown fuse, LED panel [steveo16]
Aug 05, 2009 (6:16 pm)
Not likely on the seat wiring. The BCM is under the dash to the right of the gas pedal. Other than replacing it, there isn't much you can do with it. A dealer can run diagnostics on it, but that isn't something most users would have the tools/software to do.
I would look first to the ignition switch. Were you able to determine what function was blowing the fuse?
Aug 11, 2009 (4:11 pm)
i have a97 gmc jimmy my fuel gage would only work part time i had a new fuel pump and sending unit installed it worked for about a week now it doesn't work at all .I pulled the tank down checked all the wires at the tank all seem good A friend of mine also has the same problem.Any ideas on where to check ?? I checked the fuse for gages it was good.any thoughts would be appreciated.
#416 of 609 Re: fuel gage problems [bigddetroit]
Aug 11, 2009 (5:06 pm)
I have a 1997 Jimmy and ran into the same problem.I replaced the original pump and sending unit with a aftermarket one. Soon after my gauge would work until it got down to half a tank then would drop to empty. After a couple years the pump
would not keep the pressure high enough to run right. It was only after I put in
a factory fuel pump/gauge assembley that I got the right amount of pressure and the guage still works fine. I'm not saying that's whats wrong with yours but, that
is what it took to fix mine. A GM mechanic friend of mine told me to put in the new GM pump
and it would fix mine,and it did! You might think about checking your fuel pressure
you should have 56 to 61lbs of pressure, I think I'd watch the mielage and guess on
the amount of fuel left in the tank instead of buying another &300 pump. Again,
it may not be the same problem I had but if it's not running exactly right and/or
your fuel pressure is below specs it is worth looking into. Sorry I can't pinpoint an
exact cause I hope this helps some.
#417 of 609 Re: 2002 Blazer - Ignition Swith, blown fuse, LED panel [jlflemmons]
Aug 13, 2009 (6:37 pm)
I unplugged whatever was under the seat. I put in a new fuse and it might be OK for a day or two and then some times for only a few minutes but it keeps blowing the fuse. It has to either be the cruise control or the Body Control Module.