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Radio Latest
- Thread starter jaybird
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Re: And on the 8th day...
Hi again Toups,
Great web site, very interesting.
I have no doubt that a missing ground can cause sneak circuits. Possibly the most common is the missing ground on a combination stop/tail lamp circuit. Very strange result. In all cases that I can think of, a sneak circuit caused by a missing ground will be required to pass through another load to return to ground. IE. the two loads are in series. The additional series load on the way to ground would reduce the current. If another circuit common to the same ground has a small fuse, this circuit's load is likely to have a high resistance which would reduce the current. I can't imagine a case where the sneak return due to the missing ground would "return" through the smaller fuse, or any fuse, & cause it to blow. The current is still looking for a ground path, not another source with a fuse. Need a specific example. Please pardon my ignorance.
Thanks,
D
Hi again Toups,
Great web site, very interesting.
I have no doubt that a missing ground can cause sneak circuits. Possibly the most common is the missing ground on a combination stop/tail lamp circuit. Very strange result. In all cases that I can think of, a sneak circuit caused by a missing ground will be required to pass through another load to return to ground. IE. the two loads are in series. The additional series load on the way to ground would reduce the current. If another circuit common to the same ground has a small fuse, this circuit's load is likely to have a high resistance which would reduce the current. I can't imagine a case where the sneak return due to the missing ground would "return" through the smaller fuse, or any fuse, & cause it to blow. The current is still looking for a ground path, not another source with a fuse. Need a specific example. Please pardon my ignorance.
Thanks,
D
Re: And on the 8th day...
You are definately on the right track Dave, but keep in mind, sometimes a fused circuit will be the least resistance. I have seen a few installs where there is be a sketchy ground connection, and usually someone along the path there is another ground fairly close in which the current will "jump" or a good bump will make it close.
Example: I had a friend who installed some foglights with a dedicated ground and powered off of another circuit (i.e. headlights). The ground had become shorted (corroded) for the fogs, and we discovered if you "jiggle" the cable just right, it would blow not only the fuse, but the headlights and fog lights as well.
Another example you have a light pulling 10amps and the ground is bad, the arc cause when the groud is bumped, can often exceed the rated fuse 2-3x for a split second. On a 10amp fuse, that is more than enough to blow.
And of course you have another example which is one of my favorites: I used to have a 300zx, and one day after insatlling an electric fan conversion I started the car, and everything ran fine, turned on the lights a/c ect. BUT, once the electric fan kicked in (with its no so great ground) it surged for a second about 50 amps into the connection to the body of the car. The fan was fine, but my radio and half my lights just went POOF! It took a while to figure out, but after working with a friend (PhD in Electrical Engineering) he stated they ran into a similar problem once on a system component and that what was happening was the current would be too great for the ground to dissapate and it would "bleed" back into other connections for the split second the ground was connected. (Similar to the sparks that fly from jumper cables) Once the ground was fixed and fuses replaced, everything functioned normally. (BTW, this was a robotics project which fried the controller, a modified GameBoy unit for those readers interested)
Point to the story is a bad ground can be far more damaging than you would think. Remember, at 16ga wire can for a very short time support up to 50amps @ 12v which is far more than you need to fry just about anything I can think of. And the #1 problem with auto electronics is the ground to the battery. Make sure it is 100% clean, tighten it down, then give it a little extra tug with the wrench. (Dont forget to check the connection between the clamp and the battery cable it is not new.
O.K. enought rambling from me for now.
You are definately on the right track Dave, but keep in mind, sometimes a fused circuit will be the least resistance. I have seen a few installs where there is be a sketchy ground connection, and usually someone along the path there is another ground fairly close in which the current will "jump" or a good bump will make it close.
Example: I had a friend who installed some foglights with a dedicated ground and powered off of another circuit (i.e. headlights). The ground had become shorted (corroded) for the fogs, and we discovered if you "jiggle" the cable just right, it would blow not only the fuse, but the headlights and fog lights as well.
Another example you have a light pulling 10amps and the ground is bad, the arc cause when the groud is bumped, can often exceed the rated fuse 2-3x for a split second. On a 10amp fuse, that is more than enough to blow.
And of course you have another example which is one of my favorites: I used to have a 300zx, and one day after insatlling an electric fan conversion I started the car, and everything ran fine, turned on the lights a/c ect. BUT, once the electric fan kicked in (with its no so great ground) it surged for a second about 50 amps into the connection to the body of the car. The fan was fine, but my radio and half my lights just went POOF! It took a while to figure out, but after working with a friend (PhD in Electrical Engineering) he stated they ran into a similar problem once on a system component and that what was happening was the current would be too great for the ground to dissapate and it would "bleed" back into other connections for the split second the ground was connected. (Similar to the sparks that fly from jumper cables) Once the ground was fixed and fuses replaced, everything functioned normally. (BTW, this was a robotics project which fried the controller, a modified GameBoy unit for those readers interested)
Point to the story is a bad ground can be far more damaging than you would think. Remember, at 16ga wire can for a very short time support up to 50amps @ 12v which is far more than you need to fry just about anything I can think of. And the #1 problem with auto electronics is the ground to the battery. Make sure it is 100% clean, tighten it down, then give it a little extra tug with the wrench. (Dont forget to check the connection between the clamp and the battery cable it is not new.
O.K. enought rambling from me for now.
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Re: And on the 8th day...
Thanks. I appreciate your explanation.
D
Thanks. I appreciate your explanation.
D
Keoke
Great Pumpkin
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Re: And on the 8th day...
Well the concept seems ok, but I have a hard time visualizing a ground that is both "Shorted" and "Carroded" at the same time. More to the point, Most of the examples reflected very poor wiring concepts on the part of the individual installer and are less likely to occur in well designed systems.__FWIW---Keoke
Well the concept seems ok, but I have a hard time visualizing a ground that is both "Shorted" and "Carroded" at the same time. More to the point, Most of the examples reflected very poor wiring concepts on the part of the individual installer and are less likely to occur in well designed systems.__FWIW---Keoke
Re: And on the 8th day...
Ok, the reason the fuse is blowing is something is pulling way too much power.
1. Is your alternator in good shape (~14v)
2. What else is attached to the power lead to the radio? (Clock, cigarette lighter, ect...)
3. What else is the constant power attached to?
I am betting the alternator voltage is fine and that you have a good clean circuit from what you are saying. If that is the case, it is going to be the radio, as it would be the only thing on the circuit to pull power and blow the fuse. Also, does it blow immediately, or after a little bit of time?
Ok, the reason the fuse is blowing is something is pulling way too much power.
1. Is your alternator in good shape (~14v)
2. What else is attached to the power lead to the radio? (Clock, cigarette lighter, ect...)
3. What else is the constant power attached to?
I am betting the alternator voltage is fine and that you have a good clean circuit from what you are saying. If that is the case, it is going to be the radio, as it would be the only thing on the circuit to pull power and blow the fuse. Also, does it blow immediately, or after a little bit of time?
Re: And on the 8th day...
One more opinion? Make sure you radio ground is to a good constant ground...it sounds like it might be connected to the door switch wires which serve as gounds only when the door are open (which should make your courtesy light come on) Every time you open your door, there is a spark to the ground which could be why you are blowing fuses too...constant grounding and ungrounding of the ground wire will enventually blow the fuse..a contanct ground will fix it. The radio is probably grounded well enough through the body of the radio to make it work, but not correctly enough to properly ground it.
Bruce
One more opinion? Make sure you radio ground is to a good constant ground...it sounds like it might be connected to the door switch wires which serve as gounds only when the door are open (which should make your courtesy light come on) Every time you open your door, there is a spark to the ground which could be why you are blowing fuses too...constant grounding and ungrounding of the ground wire will enventually blow the fuse..a contanct ground will fix it. The radio is probably grounded well enough through the body of the radio to make it work, but not correctly enough to properly ground it.
Bruce
Keoke
Great Pumpkin
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Re: And on the 8th day...
Hi Jaybird, I would have someone familiar with electrics look at the method constant power was picked up and supplied to the radio. For example, it would be highly undesireable to have a motor driven device's power and that of the radio connected to a common power point. A method to eliminate it would be to run a lead from the unswitched power terminal on the starter solenoid or direct from the battery to the radio. FWIW---Keoke
SO JB. look at both ends of the constant power circuit.
Hi Jaybird, I would have someone familiar with electrics look at the method constant power was picked up and supplied to the radio. For example, it would be highly undesireable to have a motor driven device's power and that of the radio connected to a common power point. A method to eliminate it would be to run a lead from the unswitched power terminal on the starter solenoid or direct from the battery to the radio. FWIW---Keoke
SO JB. look at both ends of the constant power circuit.
Keoke
Great Pumpkin
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Re: And on the 8th day...
Bruce, that is interesting since JB indicated that her inside lights never worked before.If they did connect to the door switch ground circuit and the door switch is defective you certainly would be grounding the lighting circuit through the radio,again a highly undesireable situation. However,I doubt that opening and closing the doors at the low duty cycle they are used would produce enough heat to blow the fuse should the door switch be good.---Keoke
Bruce, that is interesting since JB indicated that her inside lights never worked before.If they did connect to the door switch ground circuit and the door switch is defective you certainly would be grounding the lighting circuit through the radio,again a highly undesireable situation. However,I doubt that opening and closing the doors at the low duty cycle they are used would produce enough heat to blow the fuse should the door switch be good.---Keoke
Guinn
Jedi Warrior
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Re: And on the 8th day...
Jay, if I had that problem, I would go back to basics. I mean I would take the auto wiring out of the picture by connecting the radio DIRECTLY to 12 volts, through an inline fuse. One fused wire from the radio to the plus side of the battery and one wire directly to the ground terminal of the battery. NO shortcuts. Personally, I would make up a pair of long wires with small alligator clips on one end (for the radio) and large clips on the other end (for the battery). They come in handy any time you work with auto wiring!
Now if the radio works correctly, you know it is not the culprit. If so, just find a GOOD ground and a GOOD power source under the hood.
If it doesn't work right, you replace it.
Of course I am just an ex Aircraft mechanic, electrician and bomb-sight technician , so maybe trouble shooting cars is different. /ubbthreads/images/graemlins/square.gif
Guinn
Jay, if I had that problem, I would go back to basics. I mean I would take the auto wiring out of the picture by connecting the radio DIRECTLY to 12 volts, through an inline fuse. One fused wire from the radio to the plus side of the battery and one wire directly to the ground terminal of the battery. NO shortcuts. Personally, I would make up a pair of long wires with small alligator clips on one end (for the radio) and large clips on the other end (for the battery). They come in handy any time you work with auto wiring!
Now if the radio works correctly, you know it is not the culprit. If so, just find a GOOD ground and a GOOD power source under the hood.
If it doesn't work right, you replace it.
Of course I am just an ex Aircraft mechanic, electrician and bomb-sight technician , so maybe trouble shooting cars is different. /ubbthreads/images/graemlins/square.gif
Guinn
EMGEBE
Jedi Hopeful
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Re: And on the 8th day...
Jay.
Id suggest u just get a front half re-wire.
U can spend hours/days/months looking for all these silly little problems. I KNOW. I had all sorts of electrical problems a while back. I just bit the bullet and got a re-wire. They did a fantastic job... Had not ONE single problem yet.
from this...
to this...
[fuse box]
Strongly suggest.
Jarrod
Jay.
Id suggest u just get a front half re-wire.
U can spend hours/days/months looking for all these silly little problems. I KNOW. I had all sorts of electrical problems a while back. I just bit the bullet and got a re-wire. They did a fantastic job... Had not ONE single problem yet.
from this...
to this...
[fuse box]
Strongly suggest.
Jarrod
OP
jaybird
Yoda
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Re: And on the 8th day...
EM>>>I have a fuse box under the bonnet on the firewall. You're talking an additional box under the dash?
Okay guys. There's a LOT of information to process here. I need to read and re-read all the replies because I'm pertdurned cornfused right now.
Radio/speakers/cd all worked fine last night when I was riding. Didn't blow a fuse (now that I have spares)
And Keoke>>>the interior lights always worked before the new radio was installed. Both by opening the doors and by using the switch over the courtesy light on the dash. Only after radio #1 was installed did the light stop working by switch (still works when the doors open)
I'm getting very confused. Think I'll brew a pot of coffee, read these replies, get out my manual and see exactly how and where to start.
And FYI, was no problem with the original radio (that was in when I bought the car, not '74 original)-never blew a fuse at all. I'm certain there's some miswiring somewhere behind the radio.
jaybird=/ubbthreads/images/graemlins/crazyeyes.gif
After this project I have the fuel pump project ahead of me. (of course lack of music is more important than taking 20 tries to start) And the B goes in the hospital Sunday evening for surgery.
EM>>>I have a fuse box under the bonnet on the firewall. You're talking an additional box under the dash?
Okay guys. There's a LOT of information to process here. I need to read and re-read all the replies because I'm pertdurned cornfused right now.
Radio/speakers/cd all worked fine last night when I was riding. Didn't blow a fuse (now that I have spares)
And Keoke>>>the interior lights always worked before the new radio was installed. Both by opening the doors and by using the switch over the courtesy light on the dash. Only after radio #1 was installed did the light stop working by switch (still works when the doors open)
I'm getting very confused. Think I'll brew a pot of coffee, read these replies, get out my manual and see exactly how and where to start.
And FYI, was no problem with the original radio (that was in when I bought the car, not '74 original)-never blew a fuse at all. I'm certain there's some miswiring somewhere behind the radio.
jaybird=/ubbthreads/images/graemlins/crazyeyes.gif
After this project I have the fuel pump project ahead of me. (of course lack of music is more important than taking 20 tries to start) And the B goes in the hospital Sunday evening for surgery.
OP
jaybird
Yoda
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Re: And on the 8th day...
The radio worked fine for a couple weeks. Monday I slipped in a cd, cranked her up and ***POOF*** Does a cd pull more power than the radio? ALthough after I replaced the fuses yesterday and went cruising, cd and all, everything was fine. Maybe you're right, maybe was wrong fuse to begin with.
I'm shelfing this problem until it happens again. Back to the fuel pump I think! /ubbthreads/images/graemlins/devilgrin.gif
The radio worked fine for a couple weeks. Monday I slipped in a cd, cranked her up and ***POOF*** Does a cd pull more power than the radio? ALthough after I replaced the fuses yesterday and went cruising, cd and all, everything was fine. Maybe you're right, maybe was wrong fuse to begin with.
I'm shelfing this problem until it happens again. Back to the fuel pump I think! /ubbthreads/images/graemlins/devilgrin.gif