electrical check on grounds

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  #1  
Old 03-26-04, 06:02 PM
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electrical check on grounds

I'm trying to trace down a problem with my cruise control. It occassionally sets a code 62 which is the vacuum solenoid circuit. It has a tendency to drop out of cruise and not being able to get it to operate again. I've done all the checks on the flow chart and everything checks out. So now I'm down to checking the ground circuit. I know which circuit it ties into and where it ends on the block. What I need to know is if I can check the circuit with a dvom from the connector ground to the final connection on the block. Or is there a possibility of damaging something by putting power through it. Or is that not a good way of checking the ground. (It goes from the connector into the wire harness and I don't know where it comes out.) But I've got all the schematics for the ground circuits and connection locations. all help is appreciated as always.
 
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  #2  
Old 03-26-04, 06:11 PM
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The problem is you can do all the checks as listed, but if its not in the "failed state" they will come up good, Netting no answers.

You must check it at the time it dosen't work, sometimes easier said than done on intermittent problems.

Some times while doing a check heat or cool the componet, wiggle wires, tap, wet or any thing else you can think of to induce failure.
 
  #3  
Old 03-26-04, 06:19 PM
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it's not all that intermittent

The cruise on this car only works when I first start it in the morning. I'll put it on cruise when I get on the hwy and it works til I get to the first town. Once I use the brakes it stops working properly. When I get thru town and back on the hwy. I'll push the resume and it will take it up to speed for a little ways and stop working.
 
  #4  
Old 03-26-04, 06:24 PM
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I would check the brake switch, it is usually a different circuit than the brake lights. Also the adjustment of the switch.
 
  #5  
Old 03-26-04, 06:36 PM
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I'll check it out

I'll check that out also but I'm still wondering if the way I described the way I wanted to check out the ground circuit will work. I've also got a tsb on it for the a different way to check for a bad servo but I need to pick up a hand operated vacuum pump/guage for that. The TSB described very simalar symptoms as mine.
 
  #6  
Old 03-26-04, 10:16 PM
mike from nj
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to ohm a wire(or the ground), there has to be no voltage on it. some 'ohm' checks have you disconnect the battery first. the most accurate way to check a ground is to do a voltage drop test, but like larry said, the cruise has to be operating, and in the 'failed' condition to even have an accurate reading.


on most cruise control systems, the power for the entire system comes through a different set of contacts (than the actual brake lights) inside the brake light switch. with time, this can get corrosion, and you will have a voltage drop across the switch---meaning intermittent or no cruise. my friend's own chevy truck would go in and out of lockup after it warmed up, and all he did was take apart the brake light switch and sand all the contacts, he never had a problem after that.

i would try that first, it's free and it's easy.

bulletins sometimes lead you down a wrong path, hoping to find that exact problem, yet the bulletin was written for some obscure fault, that might only happen in 1 in a million vehicles. they can be too much information at times.
 
  #7  
Old 03-27-04, 08:09 AM
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more info

Well I didn't have any time to do anymore work on my car ( Oh by the way its 92 Olds 88 3.8 w/automatic 144.000 miles). But I went to the bank this morning and I had my scanner hooked up and it was acting the same way as previous posts, and this time I noticed that while it was losing speed my scanner said the cruise vacuum solenoid & cruise vent solenoid were indicated on and when I would touch the brakes it would indicate off. If I hit the control to reset it or the accell/ resume switch it would indicate on but no increase in speed and if I took it up to speed with accelerator it still said it was on while dropping speed. Just another little curiosity for you proffessionals to ponder. I know how you guys like figuring these things out and it really helps me.

Thanks and any ideas are appreciated and welcomed
 
  #8  
Old 03-27-04, 04:43 PM
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That could be a bad servo also.
 
  #9  
Old 03-28-04, 05:31 PM
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replaced the servo

I checked the servo according to the tsb and the servo was showing bad. So I switched it with one off of my Grand Am and it seems to be working like it should. I figured that would be an inexpensive way to find out. With the price of that simple little diaphram I want to be certain.

Thanks Again and hopefully its on to the next vehicle
 
  #10  
Old 03-30-04, 03:44 PM
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after two days

it seems to be running great. I've driven it to work for two days and filled the tank last night after work and so far have 90 miles on this tank and the guage has only moved half as much as it did before. Like I've stated earlier the mileage had really dropped off over the last 18 months. When I checked the servo like the tsb said it checked out electrically, but failed the vacumm tests. So I'm wondering if I was getting a vacumm leak thru the servo that I couldn't detect. I would like your opinions on this theory or if any of you have run into quite the same problem. Looking forward to any responses. If this is the answer to my mileage problem that would be pretty interesting.
 
  #11  
Old 03-30-04, 04:20 PM
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Your theory is entirely possible. Glad to hear you got it licked.
 
  #12  
Old 03-30-04, 07:13 PM
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Ill keep you guys updated

as to the long term condition so everyone will know if this was really the problem. Thanks Again
 
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