Using Fuses As Test Points.
12Ounce
03-27-2005, 10:16 AM
USING FUSES AS TEST POINTS.
For most of you this is no news at all, but some may not have noticed that fuses offer an easy way to test with a voltmeter.
Grab a loose fuse and take a look ... on the top edge of the fuse are two small openings thru the plastic cover ... right to the metal conductor inside. Using a voltmeter you can probe these little openings to see if the voltage is up to snuff at that particular location. Of course, if one side of the fuse has voltage and the other side doesn't ... it means the fuse has blown ... you know this and you haven't yet removed the fuse from its receptacle.
Over the past few days my '99 Winnie has been going downhill in performance. Occasionally skipping. Occasionally dying when driving at slow speed. Hard to start ... as though there was a fuel problem. When attempting to start, the instruments would crazily bounce around. Then two really strange things were added to the symptoms... the antitheft indicator would start flashing about 2 times a second ... and there was a "CHECK ANTI-LOCK BRAKING" message on the message board. ???? What was the connection??????
By now the car refused to start no matter how many cranking tries were attempted. Luckily it was in my driveway. I started to post the many symptoms here to ask for help. But then thought I should at least measure all the fuse voltages to see if any clues could be found there.
Starting at the battery box all fuse voltages measured to be at 13v or better ... that is, until I got to fuses #19 and #20. They had voltage ... but only 6 or 7 volts. Ahah! THE clue!
Flipping throught the electrical diagram book, I found that the "PCM power relay" fed both of these fuses .... apparently the relay contacts had burned to the point that current couldn't pass thru them as it should. A new relay bought the Winnie right back to life.
What was the connection between all the symptoms? Who knows or cares? The problem was solved ... not understood.
In '99 the number of circuit fuses was increased greatly in the Winnie, offering a number of additional test points for analyzing electrical faults.
But on all year models the above procedure works.
For most of you this is no news at all, but some may not have noticed that fuses offer an easy way to test with a voltmeter.
Grab a loose fuse and take a look ... on the top edge of the fuse are two small openings thru the plastic cover ... right to the metal conductor inside. Using a voltmeter you can probe these little openings to see if the voltage is up to snuff at that particular location. Of course, if one side of the fuse has voltage and the other side doesn't ... it means the fuse has blown ... you know this and you haven't yet removed the fuse from its receptacle.
Over the past few days my '99 Winnie has been going downhill in performance. Occasionally skipping. Occasionally dying when driving at slow speed. Hard to start ... as though there was a fuel problem. When attempting to start, the instruments would crazily bounce around. Then two really strange things were added to the symptoms... the antitheft indicator would start flashing about 2 times a second ... and there was a "CHECK ANTI-LOCK BRAKING" message on the message board. ???? What was the connection??????
By now the car refused to start no matter how many cranking tries were attempted. Luckily it was in my driveway. I started to post the many symptoms here to ask for help. But then thought I should at least measure all the fuse voltages to see if any clues could be found there.
Starting at the battery box all fuse voltages measured to be at 13v or better ... that is, until I got to fuses #19 and #20. They had voltage ... but only 6 or 7 volts. Ahah! THE clue!
Flipping throught the electrical diagram book, I found that the "PCM power relay" fed both of these fuses .... apparently the relay contacts had burned to the point that current couldn't pass thru them as it should. A new relay bought the Winnie right back to life.
What was the connection between all the symptoms? Who knows or cares? The problem was solved ... not understood.
In '99 the number of circuit fuses was increased greatly in the Winnie, offering a number of additional test points for analyzing electrical faults.
But on all year models the above procedure works.
garync1
03-27-2005, 10:34 AM
Thanks for the tip!!! When it comes to the elect. They some times lead me to blow a fuse :banghead:
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