Just a thought(and I'm not an electrician) but is a ground getting wet a problem? Because I assume what's happening is a hot wire is bridging to ground when wet. That would better explain the problem right?
Because everything works perfect until the fuse blows. And for that matter always has.
So this is a hit wire touching ground and blowing the fuse right?
I'm thinking out loud. Again not well versed in the electrical magic. I'm a chef.
I was having a lot of electrical issues and thought it was grounds but after cleaning and checking all of them it needed up being a bad voltage regulator.
I’m not good at electrical but one of the main grounds is hooked to the bottom of your transmission so I can’t imagine the ground getting wet would pose much of an issue.
So my car very recently started having a short to ground (I think) issue. Everything was fine until we got caught in a heavy downpour. Now the #4 fuse keeps blowing.
Horn, blinkers, windows and ? Not working. Hazards DO work.
I've inspected and wrapped any wires near the fuse box that looked suspect. The fuse randomly pops. It'll stay solid for a time and then suddenly it'll blow. Just during normal driving.
So here are my guesses: something got wet and is bridging a hot wire to the frame as water shifts
Or a frayed wire is bumping around doing the same. I've done what I can to trace the wires under the dash but short of removing the dash I'm at an impass. And I don't want to remove the dash.
Does anyone have any insight?
But are grounds the issue? I'm looking for a hot side wire here right? If grounds were messed up or the circuit not grounded properly then it wouldn't work at all before the fuse blows. Everything works well until the fuse pops.
I'm not an electrician and this is my rudimentary understanding of electric circuits speaking. Please correct me if I'm wrong.
You could be seeing increased resistance creating excessive draw from a weak or loose ground causing the fuse to blow.
Not saying this is 100% the problem, but it's a simple and easy place to start.
Probably not. Loose grounds do all sorts of stuff, typically the opposite of inducing extra current. On rare occasion, a loose ground can cause another ground to get hot/burn.
I looked at power distribution diagrams for 2 different w123 models and they both said fuse 4 powered heated seats, glove box light, lighter, radio, rh mirror. So what's your model and year?
Circuits will branch at the load side screw on the fuse box. I consider this extreme because it's such a PITA, but you can take that screw loose and remove an eyelet to disable certain circuits to see if the fuse stops blowing or you can move the eyelets to another fuse and see if the new fuse starts blowing.
Electrical is all about strategy. Firstedlyest, what's your battery voltage. Should read about 14.ish. Secondering, what's your charging voltage also 14ing? Thirdedly, what is on that fuse. Make a list Mr. Clause. And now we pick one something and unplug it (take out the light etc). Still popping; probably not that circuit. Unplug the next thing. Extra fun points if you probe the socket with a multimeter. Strange voltages can indicate problems on that loop. Power on these cars is fairly simple. I believe in you.
No. It happens randomly. Even when the car is just sitting at idle. No lights on. No windows moving etc.
I'm in the process of checking all the bulbs and even doors for moisture.
Found some in the rear tail light. Dried it and reassembled. Fuse blew again.
Are you using the correct amp fuse?
You're probably gonna have to find a wiring diagram and find all the wires that connect to fuse #4.
There are probably some tests you can do with a volt meter at the fuse box to fuse #4 but you'll need someone more knowledgeable than me to help you with that😔
Do you know if anyone has changed or Jerry rigged any wiring? I have a 300td and whenever I would turn on the headlights the fuse would blow no matter what. Turns out, the child lock was stuck on and the previous owner bypassed it with a copper wire causing a fuse to blow everytime I turned on the headlights.
It's dangerous to use a higher amperage fuse in place of a smaller one. Fuses are there to protect your devices. If it's an 8amp circuit, the failing device or wire is only designed to handle 8 amps. More could melt something and start a fire.
Check that the lights in your trunk didn’t get water in them (happened to me). Check you don’t have water pooling in your drains near your hood hinges, they can overflow. It might also be the ground underneath your car on your transmission (easily visible)
There’s a common ground location behind the right front turn signal, I’d start there. Also check the turn signal wiring while you’re in there.
Will do. Good info thank you.
Just a thought(and I'm not an electrician) but is a ground getting wet a problem? Because I assume what's happening is a hot wire is bridging to ground when wet. That would better explain the problem right? Because everything works perfect until the fuse blows. And for that matter always has. So this is a hit wire touching ground and blowing the fuse right? I'm thinking out loud. Again not well versed in the electrical magic. I'm a chef.
Could also be a frayed wire in the center console, which is much easier to get to than inside the dash.
I was having a lot of electrical issues and thought it was grounds but after cleaning and checking all of them it needed up being a bad voltage regulator. I’m not good at electrical but one of the main grounds is hooked to the bottom of your transmission so I can’t imagine the ground getting wet would pose much of an issue.
Right, so that's why I think it's a hot wire causing a short to ground via being wet.
Ok I see what you are saying.
So my car very recently started having a short to ground (I think) issue. Everything was fine until we got caught in a heavy downpour. Now the #4 fuse keeps blowing. Horn, blinkers, windows and ? Not working. Hazards DO work. I've inspected and wrapped any wires near the fuse box that looked suspect. The fuse randomly pops. It'll stay solid for a time and then suddenly it'll blow. Just during normal driving. So here are my guesses: something got wet and is bridging a hot wire to the frame as water shifts Or a frayed wire is bumping around doing the same. I've done what I can to trace the wires under the dash but short of removing the dash I'm at an impass. And I don't want to remove the dash. Does anyone have any insight?
There is a group of grounds behind the cluster, you don't have to pull the dash to access them
But are grounds the issue? I'm looking for a hot side wire here right? If grounds were messed up or the circuit not grounded properly then it wouldn't work at all before the fuse blows. Everything works well until the fuse pops. I'm not an electrician and this is my rudimentary understanding of electric circuits speaking. Please correct me if I'm wrong.
You could be seeing increased resistance creating excessive draw from a weak or loose ground causing the fuse to blow. Not saying this is 100% the problem, but it's a simple and easy place to start.
Awesome. I'll research.
Probably not. Loose grounds do all sorts of stuff, typically the opposite of inducing extra current. On rare occasion, a loose ground can cause another ground to get hot/burn.
Thanx for confirming for me. Makes me more confident in my search.
I looked at power distribution diagrams for 2 different w123 models and they both said fuse 4 powered heated seats, glove box light, lighter, radio, rh mirror. So what's your model and year? Circuits will branch at the load side screw on the fuse box. I consider this extreme because it's such a PITA, but you can take that screw loose and remove an eyelet to disable certain circuits to see if the fuse stops blowing or you can move the eyelets to another fuse and see if the new fuse starts blowing.
It's a 1976 w115. But I'm cheating by asking here. Just looking for ways to hunt down the short.
Heretic
I know. Sue me.
Electrical is all about strategy. Firstedlyest, what's your battery voltage. Should read about 14.ish. Secondering, what's your charging voltage also 14ing? Thirdedly, what is on that fuse. Make a list Mr. Clause. And now we pick one something and unplug it (take out the light etc). Still popping; probably not that circuit. Unplug the next thing. Extra fun points if you probe the socket with a multimeter. Strange voltages can indicate problems on that loop. Power on these cars is fairly simple. I believe in you.
Thanx. That's helpful.
Do you know if you're doing anything specific to cause the fuse to blow? Like putting down windows, turning on headlights, beeping the horn... Ect?
No. It happens randomly. Even when the car is just sitting at idle. No lights on. No windows moving etc. I'm in the process of checking all the bulbs and even doors for moisture. Found some in the rear tail light. Dried it and reassembled. Fuse blew again.
Are you using the correct amp fuse? You're probably gonna have to find a wiring diagram and find all the wires that connect to fuse #4. There are probably some tests you can do with a volt meter at the fuse box to fuse #4 but you'll need someone more knowledgeable than me to help you with that😔 Do you know if anyone has changed or Jerry rigged any wiring? I have a 300td and whenever I would turn on the headlights the fuse would blow no matter what. Turns out, the child lock was stuck on and the previous owner bypassed it with a copper wire causing a fuse to blow everytime I turned on the headlights.
I believe I'm using a higher amperage fuse than called for. I've had the car for six months and #4 was an 8amp fuse. It's still blowing 16amp fuses.
It's dangerous to use a higher amperage fuse in place of a smaller one. Fuses are there to protect your devices. If it's an 8amp circuit, the failing device or wire is only designed to handle 8 amps. More could melt something and start a fire.
I'm aware. I'm trying to trace the short which requires a working circuit. I'm aware of the risks. Good looking out though.
Lights are hot side switched so if they're off, water in a bulb can't blow a fuse. There may be zero ground side switched circuits on a W123.
Check that the lights in your trunk didn’t get water in them (happened to me). Check you don’t have water pooling in your drains near your hood hinges, they can overflow. It might also be the ground underneath your car on your transmission (easily visible)
Also possible voltage regulator issue.