1994 Class A chassis electrical issue

[Rhianntp]

Wow, that is crazy. The bulb will not light because it's ground has 11.56 volts that is apparently not able to get back to the negative post on the battery. You should not even be able to get a reading if everything has battery power which is confusing because it would be like putting both the black and red probes on the positive post of the battery no differential no voltage. You would think something would burn with the frame reading 11.56 volts. Go to the starting battery and put the meter to measure 12 volts. Put the red lead on the shinny metal frame and the black lead on the center of the center of the negative lead post of the battery with the running lights on and see if you get a voltage reading. Let me know what it is.

I'll try what you said tomorrow

 

[Rhianntp]

if the stop light switch on the pedal is bad could it do this?

 

[bullfrog]

Well you said your continuity check between the the socket metal housing where the bulb is secured and the shinny metal frame showed continuity right so if you have 11.56 volts at the socket you should have it at the shinny frame, I bet you don't as your meter is grounded there and you got a reading. Turn off the running lights and do not activate the brake and try taking the wire nut off and disconnecting the wire that goes to the ground from the socket and do a continuity test again. If you get continuity something is shorted out so then do between the frame and the wire going to the frame after you disconnect it from the part of the wire going to the socket. Then check continuity between the part of the wire going to the socket and the metal inside the socket possibly the socket or the wires have shorted out. Go ahead and check between the frame and both pins in the bottom of the socket for continuity to the frame as well. Also no a bad break light switch would not as it simply is allowing power to flow in the circuit it doesn't control where it goes.

 

[Rhianntp]

Ok, that's a lot of stuff to try.. I'll give it a shot tomorrow .. thanks

 

[Rhianntp]

I really appreciate everyone's efforts in helping me get this worked out. I'd be lost without this advice

 

[bullfrog]

Well since you don't have enough to do be sure to check the fuses as well. We should have blown fuses if we have any shorts. Really proper trouble shooting starts at the positive battery terminal and checks for power at the fuse links, fuse block, fuses, switches, lights, grounds on the frame and the frame back to the negative battery post. Guessing like we are is a gamble when trying to find a problem so far we haven't been very lucky! Lol!!! Now you know why garages charge so much! Your apprenticeship is moving right along! Now if the slow internet would get a little better it would help!

 

[Rhianntp]

Haha  
Every fuse I have been able to find isn't blown. I only know of those two fuse blocks in the pictures. There has to be others doesn't there? I mean where are all the fuses you normally see under the hood? Could they really run everything off those two in the picture?
Hopefully doing what you said with the sockets/wires tomorrow will give better clues.

 

[Rhianntp]

"I am able to see 2 fuse links under the "hood"  a 20 amp and a 30amp.. they both are good."

So you checked them both with your meter,  right?

Also that wire I have been telling you about on the starter HAS a fuse link on it somewhere have you check that?

That big fuse block is factory GM. You can see,  tail lps, stop haz,  and turn bu.  have you checked all those with the meter.  the first 2 of those should be hot with the key off.  the trun bu should be hot with the key on.

Highdesertranger

Sorry for the delay.. I have crawled under there a lot now and only see that those wires go up and into a loom and wind up somewhere near the thermostat housing. I'll look under the dog house again for any links they might have... the only fuse links I can see anywhere inside the hood are what looks like a 30 amp that goes to trailer brake controller thing, and a 20 amp that I have no idea what it does near the firewall. I pulled both of them and they aren't blown and do not look corroded at all. I still am not sure how to test the fuse block and its fuses. Just voltage ? Black probe to bare metal and red probe to each side of the fuse if i can fit it in there? Thanks

 

[bullfrog]

Fuse links are simply a different type of fuses. They are made of fine wire inside a very heat resistance insulation. They look very similar to regular wire but usually thicker. The wire melts inside the insulation when it tries to carry too much current ( this causes the insulation to get very weak and flexible sort of like a rubber band so many times you can feel if the wire has melted and pull the insulation apart). You can test them with your volt meter since most are used where they have 12 volt battery power when installed you simply check for 12 volts coming out of the wire after the fuse link section. One usually goes to the alternator and the other to the fuse block. In your picture the wire coming off the starter should have at least one for both wires or two one for each wire.
Fuses can be checked with the volt meter as well as you described just read HDR's post to see which ones you have to have the key on to check. PS you may have to file the tip of your red lead to a little finer point to get to the recessed metal part of the fuse in the top on either side

 

[bullfrog]

In your picture of your starter the yellow wire with the blue heat shrink that turns to red appears to have some black writing on it can you read it? That wire after the fuse link and another wire splits off with a fuse link connects to the fuse block where the stop/haz and tail lps fuses get their power. Head lights also get power from that wire as well. It looked like in the picture of the fuse block above those fuses under the gray wire the fuse block terminal and plastic was melted. I'm also wondering about that second fuse block as it does look like it was mounted at the factory, can you tell what the wires run from or to. Pictures always help thanks!

 

[highdesertranger]

Ok I would like to add that I was getting discouraged. It seems you were ignoring important advice. But I believe it's because of your lack of knowledge so I will try again.

First off you can not tell if a fuse or a fusible link is bad by looking at it. Sometimes it's obvious but sometimes it's not and it will look good but it's not.

I searched on you tube and found many videos of people giving bad advice on how to check fuses and fusible links. However I found this short video that gives a good explanation of how to check both. Please watch this and follow the advice given then come back and tell us what you found.



Make sure you check all the fuse links. That one on the starter is a fusible link, check it. Don't just look at it check it.

Highdesertranger

 

[Rhianntp]

Thanks a lot, I'll watch the video 

 

[Rhianntp]

Are these fuse links? How do they come apart if so

 

[Rhianntp]

In your picture of your starter the yellow wire with the blue heat shrink that turns to red appears to have some black writing on it can you read it? That wire after the fuse link and another wire splits off with a fuse link connects to the fuse block where the stop/haz and tail lps fuses get their power. Head lights also get power from that wire as well. It looked like in the picture of the fuse block above those fuses under the gray wire the fuse block terminal and plastic was melted. I'm also wondering about that second fuse block as it does look like it was mounted at the factory, can you tell what the wires run from or to. Pictures always help thanks!

Thanks   I don't see where you mean in the fuse block picture..where does something look melted?

 

[Rhianntp]

Ok I would like to add that I was getting discouraged.  It seems you were ignoring important advice.  But I believe it's because of your lack of knowledge so I will try again.

First off you can not tell if a fuse or a fusible link is bad by looking at it.  Sometimes it's obvious but sometimes it's not and it will look good but it's not.

I searched on you tube and found many videos of people giving bad advice on how to check fuses and fusible links.  However I found this short video that gives a good explanation of how to check both.  Please watch this and follow the advice given then come back and tell us what you found.



Make sure you check all the fuse links.  That one on the starter is a fusible link,  check it.  Don't just look at it check it.

Highdesertranger

That video helped A LOT.. I'll report back with results

 

[Rhianntp]

Ok.. tested every fuse in the fuse blocks I know of under the dash with the light probe method.. they all pass

 

[Rhianntp]

Wow, that is crazy. The bulb will not light because it's ground has 11.56 volts that is apparently not able to get back to the negative post on the battery. You should not even be able to get a reading if everything has battery power which is confusing because it would be like putting both the black and red probes on the positive post of the battery no differential no voltage. You would think something would burn with the frame reading 11.56 volts. Go to the starting battery and put the meter to measure 12 volts. Put the red lead on the shinny metal frame and the black lead on the center of the center of the negative lead post of the battery with the running lights on and see if you get a voltage reading. Let me know what it is.

Tested for voltage on the frame as you described .. none

 

[bullfrog]

That is a good thing! So that tells us we need to find out what is happening at the socket metal holder that was in your hand in the picture. Go ahead and do the tests with it's wire nut I described a few posts back #123. Let me know what you find. You really should replace the wire nuts with proper connections by the way.

 

[bullfrog]

Your picture is the fuse links and they are not designed to come apart. You can sharpen your red lead probe or like you did with your frame ground clip make an adaptor and solder a straight pin to the end of the wire to probe into the red wire on either end of the fuse link. If there is a nearby terminal on the red wire it goes to you can check there as well as long as they directly connect to the fuse link. Be careful as it is easy to short your red lead or its connections when using an adaptor so tape them or take precautions to prevent grounding while testing. Main thing is you should have battery voltage going in and battery voltage going out.

 

[Rhianntp]

That is a good thing! So that tells us we need to find out what is happening at the socket metal holder that was in your hand in the picture. Go ahead and do the tests with it's wire nut I described a few posts back #123. Let me know what you find. You really should replace the wire nuts with proper connections by the way.

Just to let you know when I post results of something it doesn't mea I ignored other things you guys asked me to do, it just means i haven't done that part yet    If this ever gets resolved I have the connectors/crimpers/ and heat shrink stuff to hook it up right :thumbsup: