Electrical Gremlin In 2000 Silverado

[chuckmc8]

[2000 Z71, 5.3 165K miles Electrical Gremlin

I have owned this truck for 2 weeks and received no past history. I would not buy any vehicle with elect probs, but it "is what it is". Love the truck, tho!

I have decided to put a few thousand miles on it to acumulate data and symtoms before diving off into tossing money at it, so at least being able to find a direction in which to look. i am posting the symptoms that I can identify to see if someone here has had similar issues and can point me in the right direction.

1. Fuel Gauge is operates intermittently I was aware that these truck were prone to have fuel gauge sender issues, so I am/was prepared to change the pump and sender ($270 plus tax at Advance) I figured this in the purchace price. I dont want to 'piss away' $300 and a day if it doesnt help the situation. The guage will always indicate zero and the low fuel light on when initailly starting the engine. After a few miles of driving, it will usually read correct fuel level. Then,after a few minutes; or coincidentally[b] another device powers on or off, such as the a/c compressor or cruise, it shuts off the fuel gauge.

2.A/C Cycles off but doesnt cycle back on

I had posted this kuestion(SP) (how do you say that correct button doesnt work on my keyboard?)

And received great advice and I thought that I had narrowed it down to needing the air-gap adjusted on the compressor. (Air is ice cold and I have replaced the cycle switch) When the compressor cycles off and wont turn back on, I can hold metal object to the compressor clutch and it has magnetic field, So, to me that indicates that the signal is getting to the clutch to 'click back on'

if I depress the a/c button to turn it off (when it has Kuit) (again, sorry) wait about 5 mins and press it back on, it will come back on and all is Kool (habit now) until it cycles back off and repeats the whole thing.

Where it gets real dicey now is that yesterday, drove for a while and it did the regular thing as describe above. I selected the a/c to be 'off' and rolled down the window.

"fresh air" set on the dial, cold setting on the control and blowing the 'face vents' only....

And the compressor comes on.....

As I said above, the weird thing is that the cruise engaging or a/c engaging knocks out the fuel gauge on the dashboard. This truck is very highly optioned, (I guess it has all that could be ordered) and the only accessory that does not work are the power mirrors and the interior light does not come on when the door is opened.

I have checked fuses and tried to remove the relay, but i couldnt get the relay to budge outy of the underhood panel. don't the relays just pull straight up? I also had a freind try to get one out, but we pulled on them untill almost the 'point of breaking something" so we stopped. Is there some type of release to remove the relays from the panel?

 

I am suspecting a connection problem in the wiring or a bad ground.

 

Thanks for taking the time to read and please post suggestions-

[bill190]

For a problem like this, I would do some basic checks first. Go through the basic electrical system to be sure the basic electrical supply is ok.

 

The A/C clutch is an electromagnet. The more electricity, the stronger the magnet. Or the less electricity, the weaker the magnet!

 

And a fuel gauge can work on current, which is sort of like water pressure, or how much electricity is getting to the device. Electrical "pressure" if you will!

 

So let's first be sure there is enough electricity there to power this stuff. Turn on the ignition but don’t start the vehicle. You should read about 12 volts on the battery with a multimeter.

 

Then start the vehicle. Now you should read about 13 to 14 volts on the battery with a multimeter. This means the alternator is charging.

 

By the way, does the vehicle ever crank slowly when starting? Like it has a weak battery?

 

If your battery terminals are not clean, clean them with a battery terminal wire brush tool. Wear glasses or safety glasses as the brush can flick the particles into your eyes.

 

Next do a "voltage drop test". This checks for poor electrical connections. Turn the ignition on, but don't start the vehicle. Do this with the main positive wire from the battery and the main negative wire from the battery to the body. Check from the battery terminal to the connector on the wire. Then at the other end of the wire, check from the wire connector to the post (bolt/screw) that the wire is attached to.

 

Next check the main negative (-) wire at both ends. And check the main negative wire going to the engine block.

 

Next start the vehicle and check the connections to the alternator. Again check the main battery negative wire to the engine block.

 

You can't do this test with battery side terminal connections or with some alternator connections because the wire connector covers the connection. In that case, turn off the ignition, remove the connector, be sure it is clean, then reattach. Make sure it is snug.

 

Here is how to do voltage drop testing...

http://www.engine-light-help.com/voltage-drop.html

 

Next when your A/C compressor stops working. It is possible it is not getting enough electricity to make the electromagnet strong enough to engage. Or it may be defective when warm.

 

You can test for this. When it stops working, yet there is power to the wire... Try disconnecting the connector at the compressor and running a jumper piece of wire from the compressor wire directly to the battery. (I use a heavy gauge test wire which has a high amperage in-line fuse like 30 amps.) See if the compressor engages or not.

 

If yes, then check backwards on the A/C compressor circuit for poor connections. You already checked the engine block ground, so that should be OK. The A/C compressor circuit should also have a relay which should be checked if this is a problem.

 

If the compressor does not engage, then best to replace the compressor. The thinking here is that once the compressor clutch starts to go out, the compressor is worn as well and will likely go out in a short period of time. When a compressor fails, it can send metal particles into the A/C lines and this becomes a mess! So best to replace the whole thing.

 

Then see if all this solves the fuel gauge problem.

[chuckmc8]

Thanks Bill, I will try this and post results. Chuck

 

 

For a problem like this, I would do some basic checks first. Go through the basic electrical system to be sure the basic electrical supply is ok.

 

The A/C clutch is an electromagnet. The more electricity, the stronger the magnet. Or the less electricity, the weaker the magnet!

 

And a fuel gauge can work on current, which is sort of like water pressure, or how much electricity is getting to the device. Electrical "pressure" if you will!

 

So let's first be sure there is enough electricity there to power this stuff. Turn on the ignition but don’t start the vehicle. You should read about 12 volts on the battery with a multimeter.

 

Then start the vehicle. Now you should read about 13 to 14 volts on the battery with a multimeter. This means the alternator is charging.

 

By the way, does the vehicle ever crank slowly when starting? Like it has a weak battery?

 

If your battery terminals are not clean, clean them with a battery terminal wire brush tool. Wear glasses or safety glasses as the brush can flick the particles into your eyes.

 

Next do a "voltage drop test". This checks for poor electrical connections. Turn the ignition on, but don't start the vehicle. Do this with the main positive wire from the battery and the main negative wire from the battery to the body. Check from the battery terminal to the connector on the wire. Then at the other end of the wire, check from the wire connector to the post (bolt/screw) that the wire is attached to.

 

Next check the main negative (-) wire at both ends. And check the main negative wire going to the engine block.

 

Next start the vehicle and check the connections to the alternator. Again check the main battery negative wire to the engine block.

 

You can't do this test with battery side terminal connections or with some alternator connections because the wire connector covers the connection. In that case, turn off the ignition, remove the connector, be sure it is clean, then reattach. Make sure it is snug.

 

Here is how to do voltage drop testing...

http://www.engine-light-help.com/voltage-drop.html

 

Next when your A/C compressor stops working. It is possible it is not getting enough electricity to make the electromagnet strong enough to engage. Or it may be defective when warm.

 

You can test for this. When it stops working, yet there is power to the wire... Try disconnecting the connector at the compressor and running a jumper piece of wire from the compressor wire directly to the battery. (I use a heavy gauge test wire which has a high amperage in-line fuse like 30 amps.) See if the compressor engages or not.

 

If yes, then check backwards on the A/C compressor circuit for poor connections. You already checked the engine block ground, so that should be OK. The A/C compressor circuit should also have a relay which should be checked if this is a problem.

 

If the compressor does not engage, then best to replace the compressor. The thinking here is that once the compressor clutch starts to go out, the compressor is worn as well and will likely go out in a short period of time. When a compressor fails, it can send metal particles into the A/C lines and this becomes a mess! So best to replace the whole thing.

 

Then see if all this solves the fuel gauge problem.

[chuckmc8]

Is there any circumstance when the compressor should engage w/o the a/c selector initiated?

With the a/c button "de-selected", when switching from 'fresh' to 'recirc', the compressor will engage when the 'recirc' button is selected.

There is a complicated explanation of the system in the owners manual, but I couldnt decide if this was normal? Ideas?

[bill190]

Yes, but I will reword the "should" to "could"!

 

A/C when running will remove humidity form the air. And this is a great way to clear up a foggy window in the winter. So you would run it with heat/defrost on full blast and the A/C compressor running or perhaps for a little bit.

 

Some systems do this automatically. Others don't do it at all.

 

Then also it is a good idea to run the compressor every now and then to circulate the oil in the system. Some systems do this for a little bit when turning on the heating in winter, others don't do it at all.

 

So depends how they designed the system. It "could" do this! (And it is a good thing if it does...)