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Chevy Blazer GMC Jimmy Electrical Problems



  • jlflemmonsjlflemmons Posts: 2,240
    Follow on to what cardoc said above, you may have a battery plate (internal) that is coming apart. Will short, put a big load on the alternator, then when you hit the rumble strips, vibration knocks it free. Cheap easy way to know if this is happening is to feel the battery cables when you see the voltage drop on your meter. If those puppies are getting hot, the alternator is cranking amps, and the battery is sucking it down.

    All that being said, your "new" alternator may be having issues. Cruising on the road in daylight hours with the fan on low, you are not putting much stress on the alternator at all.

    By the way, that gas gauge problem you are seeing is a software issue with '99-'02 GM trucks. Instead of buffering the gas slosh in the tank with a baffle, the designers used software to "average" the signal coming from the sending unit to the BCM. Problem is, some code junkie only conditioned the signal when the vehicle is in drive, not reverse, or park. Want to see something cool? If you back out and the gauge drops and turns on the "low fuel" lamp, put the vehicle in drive and get moving up to about 20mph or so. Shift the tranny into neutral and put on the brakes. The fuel gauge will swing back up to the true reading. Before you stop, shift back to drive. This kicks the software back into "averaging" mode and the gauge will behave normally.

    You don't want to know how long it took me to figure out what was causing this! :D
  • dp2226dp2226 Posts: 28
    I have a 1999 Chevy Blazer, about 157,000 miles

    Like clockwork after 30 minutes, the abs will kick in under light pressure and the abs light will come on and stay on. After turning off the car for while it turns off then will repeat.

    Both the wheel hubs and sensors are new, the rear one is not but I cleaned them all just to double check. Did not see any issues with worn wires. The problem started months after I replaced the wheel hubs.

    I have only had the blazer since the spring and would notice the pedal would chatter a little when backing down my drive way which is a slight incline. Thought it was due to rear wheel bearings which I have not attempted to replace yet.

    Looking online found you can get the module rebuilt. Before I attempt to take this out was looking for other options.
  • I can only tell you what I had to do. Tighten the rear shoes just enough to touch
    the drum. not drag or hold back. Bleed the entire brake system starting with the
    right rear (farest away) and work your way up to finish at left front. Try it then and see what you have. It should be ok. If not bleed the module. I do not know where you start there or the exact procedure. I may have it in some of my manuals but,
    you probably have one or have access to one. I know when your rear shoes need
    replaced or tightened That brake pedal and the noise the antilock module makes
    sounds like the blazer's falling apart. It's funny to me when mine has done it over
    the years.You don't need rear wheel bearings unless you see dark moist thick
    oil caked on the inside of the rear wheels.When a bearing goes out the seals
    warn you first.Just try the rear shoe adjusting and bleeding first and you will be
    surprised. That antilock brake system GM came out with is a joke.Every GM
    vehicle with that system should be recalled for a less complicated normal system.
    Sorry I said it's funny to me but I know how you feel. Good luck pal.
  • dp2226dp2226 Posts: 28
    Sounds good and I will give it a try. I did have a new master cylinder put on in the summer and rear calipers. Maybe there is some air left over or something.

    Does it matter if I have disc brakes vs drum brakes? I hate the aluminum calipers, stripped the bleeder on the first set just putting them on.

    Did your blazer do it after driving for almost the same amount of time?

    Thanks for the tip on the rear wheel bearings, back end sounded a little loud to me. The seals are definitely not leaking. Guess I am paranoid after finding out the first cause of a loud ride was the u-joints.
  • I was'nt aware you had rear discs.As far as mine,like I said when the rear shoes got thin it would do it. Generally a car will go through 2-3 pairs of front pads to one set of rear shoes. Disc brakes really set themselves because as the pads get thin
    the piston in the caliper goes further and further out with no slack between the piston and brake pad. I like aluminum calipers on motorcycles and ATV;s but on
    a vehicle like ours,no way. I suggest you quickly crack the bleeders and close them
    immediatly(to see if they are going to loosen or strip)Now comes the fun.Bleed the system from rear to front. Oh yea, if your calipers are corroded,the piston may stick
    and the pads will chatter if they are just lying there unassisted and there goes your light and antilock noise.Check the calipers repair or replace as needed. Bleed the
    heck out of your brakes starting at the farthest away working forward.Your last one
    should be left(drivers side) front.I think you'll find this to work.If not,have your under
    hood antilock module checked.It has a printed curcuit board that can easily be replaced too.I would leave that one to someone else after getting bleeding instructions first. Good luck.P.S.Wanna buy a used Jimmy? LOL.I feel you'll get
    it this time around. Good luck pal.
  • dp2226dp2226 Posts: 28
    Definitely will give it a go. The front calipers are old so will check them out.

    I just popped the abs module out and unfortunately it is a Hayes 310 which according to a couple sites it cannot be rebuilt
  • Thanks, I'll give that a try too. Sounds easy enough to fix. :)
  • dp2226dp2226 Posts: 28
    I posted this a while ago and was given some good tips but have not solved the problem. The front left caliper was bad so I replaced it but running into the same problem where the ABS light goes on after 30 minutes of driving

    It is a 1999 Chevy Blazer

    Both Wheel hubs with sensors new, calipers, rotors, and pads all the way around, master cylinder. The abs modulator is a Hayes 310, cannot be refurbished, no idea if it is good or not. I believe the brakes are properly bled. I also checked the wheel sensor connections to see if loose or dirty. I was only able to test the resistance which was 1 ohm each. I know there is a 3rd sensor on the drivetrain but have no idea if it is good.

    Before I drop $100 on an ABS Diagnostic tool, any other ideas?
  • have same exact problem with the fuse for the actuator fuse is fine till i drive the vehicle when idling it is fine can put it in and out of gear if you dont go thought it was actuator so found used actuator $140.00 still same problem
  • On 4 wheel disc brakes with 4 wheel anti lock brakes,there is a sensor at all 4 wheels.If you haveRWALock system it only controls lock up of the rear wheels.If you have RWAL only the sensor should be in the tail shaft of the transfer case or if two Wdrive on the tail shaft of the transmission.I am assuming that you have a 4x4.
    If it's a RWAL system,the control unit(brain) is mounted at a different place but still easy to access. The wheel speed sensors and brake light switch sends info to thecontrol unit to monitor hydraulic line pressure to avoid wheel lockk up.It also constantly monitors the system to find faults in the system.When something goes wrong in the system, the"BRAKE" or :ANTILOCK" light will come on.A code will then be stored. The code reveals the problem.Now, getting the code of course requires a special scan tool. Some of the newer scanners will give abs trouble codes too If not you have to use one made for the abs system only. After getting the code(s) you'll have to use the tool to erase the code(s).That's the only way.Check all wireing connections,If you have different size tires and wheels other than factory,It WILL cause the Light to go on also.There can't be a 10 percent variance in
    speed sensors and tire size.That can be recallibrated with a scan tool.I don't know what is making your light(s) come on and without a scan tool, you may never know
    I was just shareing some info I knew about the system hoping it may help. Good luck sir,
  • dp2226dp2226 Posts: 28
    Thank you for the advice. You started to help me orignally and were right on checking the calipers up front. One was bad and bled the heck out of them like you said. It was a huge help. Brakes even smoother now. I will look into the scan too. It may be the error code needs to be reset or can at least direct me to the problem.
  • I just bought a used 6 cyl 1997 chevy blazer. It seems after all night ,in the morning it wont start untill I try about 6 times. Once I get it started its not that big of a problem. She will start easier. Also when it is in gear ideling I have to feather the gas pedal to get it moving or it will stall ( I can start it right after that). I have no problem with acceleration and dont seem to have any power loss when I am driving or going up inclines. I can hear the pump go on. I dont know if this helps but I believe the fuel gage is not working properly either It wont go over a 1/4. The truck sat for about 7 mos because he couldnt get it started at all.
  • Don't worry about the fuel guage right now.Very few Blazers and Jimmys fuel guage works properly in that year model. You need to replace the fuel filter,do a
    basic tune up and check the fuel pressure.In the air filter box when you replace the filter,you may even find that chipmunks or field mice have made a home there.
    After all this see what you find. What did you do to get it started? Make sure the
    fuel tank is full of fresh fuel. Did the previous owner change the fuel pump? There are mistakes that people make when they do this.Do this and see what happens.
    Fuel pressure should be between 54 and 61psi.
  • Thanks for the advice. I will try that. When I went to but it it almost would even turn over then we hooked up jumper cables and ............... it started right up! He claimed he couldnt get it started for over 7 mos. I did purchase a new battery.

    Thanks again I will let you know how I make out
  • Also you have to consider that you have bad gas in there, after 7 months, unless you've burned it all up already.

    Other than that, you might check the fuel pressure regulator. If it's bad, it will cause hard starts when the car's been sitting. You can pull the vacuum line off the fuel pressure regulator and if there's any gas in there, it needs replacing.
  • ok thanks

    I dont want to look stupid here but where is the press reg?
  • You have to take the upper manifold off, so you might want a workshop manual if you're planning on a DIY. But there's a pressure test connection (looks like a tire valve) that you can hook a fuel pressure gauge to. With key ON and engine OFF, pressure should read 60-65 psi.
  • dp2226dp2226 Posts: 28
    I do not want to jinx myself but after replacing the defective caliper, bleeding the heck out of the brakes. I had one instance of the abs light coming on and did not do the issue where the abs kicked in at a low speed. May of been a combo of the bad caliper and air in the lines. The code may of needed time to reset as well.

    If you ruled out bad or dirty sensors and are driving your self nuts, a good bleeding, and checking calipers would be a good place to start.

    I used a vacuum hand pump to bleed them. $30 well spent once everything was bleeder screw sealed properly with a little teflon tape.

    Thank you Cardoc50 for the advice
  • There is something every Blazer/Jimmy owner should know.... Every year from
    1995 up has changes made to the wiring, fuel system,brakes and a lot more. That
    makes things hard to diagnose. Every year they change something. That my
    friends is hard even for a mechanic to keep up with. So be patient if it takes me
    a while to figure a problem out. I will do my best to help anyone.
    Thanks dp2226
  • I have a 96 blazer I was driving and made a left hand turn and heard a pop and dashboard gauges with the exception of fuel gauge quit working, I troubleshot fuses and dash fuse was bad replaced it and everything was cool took off and fuse popped again and now will take about 1 second to pop fuse. Blazer still runs and drives but kinda hard for me to judge speed and it is nice to know oil pressure and other info any ideas thanx explorer62
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