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Chevy Blazer GMC Jimmy Electrical Problems

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  • so i started reading through the forum pages to see if any one else has had the problems i have had with these lights and after reading quite a few pages, i figured i would just post a thread, so i appologize for being redundant. so im working on a 95 jimmy 4 wd 4 door. the runnig lights work fine (head lamps, hi and low, parking lamps, front and rear) but the insturment lights are out, the brake lights dont work (including high mount) and no turn signals work at all including the 4 ways. i know the brake switch works because it kicks the cruise controll off when you hit the brakes, and when you hit the turn signal lever to signal left or right it sounds like the flasher lets out one click, but no lights light up. it could be a circuit breaker and not the flasher though. all the fuses on the left side dash are fine and there is no power to the signals at the sockets, so its not a ground issue. if some one could give me an idea of whats wrong that would be great, i dont want to have my buddy spend 250 on a multi function switch if it could be something else. thanks for your help.
  • tidestertidester Posts: 10,110
    there are more things than just over current that can blow a fuse

    I'm curious. Can you elaborate?

    tidester, host
    SUVs and Smart Shopper
  • jlflemmonsjlflemmons Posts: 2,240
    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.
  • tidestertidester Posts: 10,110
    Thank you for that reply - very informative and helpful! :)

    tidester, host
    SUVs and Smart Shopper
  • 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?
  • jlflemmonsjlflemmons Posts: 2,240
    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.

    [edit] On the fuse issue, try turning off the cruise control switch on the stalk, and (considering it is 103 here today :surprise: ) 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.
  • cardoc50cardoc50 Posts: 49
    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
  • 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?
  • jlflemmonsjlflemmons Posts: 2,240
    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?
  • 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.
  • cardoc50cardoc50 Posts: 49
    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.
  • 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.
  • cardoc50cardoc50 Posts: 49
    Hello jlflemmons,I'm going over to the Chevrolet garage today to talk to my friend
    about your problem. I will let you know what he says. I tell you, I have never seen
    so much electrical problems on these Blazers and Jimmys in my life. GM has 43 technical service bullitens on them and several recalls. I'll be back...
    Thanks for your patience...
  • jlflemmonsjlflemmons Posts: 2,240
    Hey, cardoc, I assume you mean the problem steve is having. Thanks for the help.

    I know there were major electrical issues with the 2nd generation when it came out. Sometime during this generation there were some major improvements made in the harness designs that helped. But these are still one of the early generations that had a BIG increase in complexity.

    You want to see one that will really mess with your head? Check the door jamb switches. On my '02 2dr, there are no wires to them! The BCM has a remote sensor/switch inside the door that reads the latch, and turns on/off the interior lights accordingly. Bizarre.
  • cardoc50cardoc50 Posts: 49
    They call that up to date computerized improvements that a normal person would have to take it to the GM dealer to have fixed. They'll pull out a TSB and have it fixed in an hour and the fee? Ha Ha. I talked to my friend about your problem and he was nameing off stuff I've never heard of so I just cut it short and left. There are more sensors on these things than anything I've ever saw. The thing is,a sensor not related to a problem we might have can cause a slew of non related problems. Why
    would they put that in the door to turn off the interior lamps? I thought the switch
    was fine. It worked for 50 or so years! LOL. I'm going to the Ford store and trade mine in on a new Fusion. lol
  • jlflemmonsjlflemmons Posts: 2,240
    I swear the only thing I could come up with on the door switch was that they already had the hole molded in the dash endcap, and had a boatload of switches to get rid of. The first time I came across this I spent a good 15 minutes looking for the harness connector that "must have been pulled off" before I realized that all the functions were working normally without the switch connected, and then looked close enough at the harness contacts on the switch to see that they had no marks from having ever been connected.

    Very odd, and I don't know for sure exactly what year they did this.
  • cardoc50cardoc50 Posts: 49
    I need help. My 1997 Jimmy 4x4SLE will only start when you release the key. I crank the engine and it cranks normal but will not start until you release the key.
    That means most of the time it won't start because you only have a second before
    the key is on the on position. Of course the first thing I thought of is the ignition switch. It has the high output csefi engine or OBD 11 as it's called. Remember it is a 1997 year model. My question is simple...Where is the actual ignition switch on my model? I know this will sound stupid to a lot of you guys but,stupid is as stupid does! lol. Please help.The Jimmy looks brand new and I've kept it that way. I want
    to drive it again. I've even let the registration run out.(no tags) Now it just sits in one side of my garage looking pretty. If you think it's not the switch, I'll surely take any
    idea and look into it. "WHERE IS MY IGNITION SWITCH?" and to think I'm a retired mechanic with 38 yearts of service! I'm anxiosly waiting for a reply.Thank you so very much.
  • cardoc50cardoc50 Posts: 49
    I found the ignition switch on the 97 Jimmy. Of course it's by the key switch under the steering wheel.lol I know on most Fords they use a rod connecting the key switch down the steering column to the ignition switch mounted low on the steering column. Thanks cardoc for letting yourself know where it's located! LOL I'm not only geting old but I think the word senile may fit in there somewhere.
  • jlflemmonsjlflemmons Posts: 2,240
    Sorry I didn't see this sooner, bud, I coulda helped. What you found on your Jimmy is pretty typical on GM. Did you have any trouble getting it swapped out?
  • cardoc50cardoc50 Posts: 49
    Sorry I got you and Steve mixed up earlier. No I have'nt got to it yet. My wife's still in the hospital and I just found out my Big brother has cancer and they found it too late it's in several places and in his lymphnodes.
    My Jimmy's the year where you use a screwdriver to bend the spring away from 4 notches and then remove the horn (airbag). then I can get to the steering wheel and then the switch. Guess what the switch cost? I may have you send me some money! LOL 17.69. Seventeen dollars and change. Thanks friend. I'll let you know
    how it goes. I also heard it was a common problem on those vehicles.Thanks again
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