When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
While out driving last night, everything was working fine. Started to get a solder type smell in the cab; pretty strong smell. Then, while clicking the dimmer switch back to low beams, the lights went completely out. I quickly clicked back to high beams, which continued to work fine. All four bulbs are on for high beams. Pulled over and tried it several more times, and low beams were completely dead.
I'm thinking it's the headlight dimmer switch, but any input is greatly appreciated, as I'm just guessing.
X2. Before replacing anything, check for voltage on the low beam terminals (brown wires) at the headlight plugs when the dimmer is in the low beam position. If none, then check at the brown wire where it comes out of the dimmer. If again none, it's the dimmer switch.
Thanks guys! I was working on the car all day doing other things. I ended up just pulling the dimmer switch out, since that was my initial inclination. The switch had completely fried and melted part of the female wiring harness, as well. I was able to find both parts in stock locally. Installed, and the lights are working properly again.
Thanks guys! I was working on the car all day doing other things. I ended up just pulling the dimmer switch out, since that was my initial inclination. The switch had completely fried and melted part of the female wiring harness, as well. I was able to find both parts in stock locally. Installed, and the lights are working properly again.
_______________________________________________
Glad you got it fixed. Future such events are entirely preventable if you would rewire with relays so you are not running 10-15 amps through headlight and dimmer switches. Relays let you operate the switches with 1 or 2 amps at most and they handle the heavier load. Much easier and less expensive to replace a relay. At the price of NOS or reproduction switches a $4 Bosch type relay is an investment. Lots of information on line on how to wire headlight circuit with one or more relays. (some obsessive/compulsives use a relay on low and another on high beam so you will always have one set working ).
Jerry
Future such events are entirely preventable if you would rewire with relays
While adding several new and exciting failure modes...
Sorry, but I have to disagree. The original wiring, switches, and connectors are more than adequate for the current in this circuit. The failure in the dimmer switch was a mechanical one, and a relay would not have prevented that. As with engines, transmissions, suspension, and all other mechanical parts of the car, after so many cycles, the parts fail due to fatigue. These cars were never designed to last 50 years. Simply replace the failed dimmer switch with a quality replacement and it will likely last the lifetimes of the next two owners, especially if the car is relegated to weekend and summer use.
While adding several new and exciting failure modes...
Sorry, but I have to disagree. The original wiring, switches, and connectors are more than adequate for the current in this circuit. The failure in the dimmer switch was a mechanical one, and a relay would not have prevented that. As with engines, transmissions, suspension, and all other mechanical parts of the car, after so many cycles, the parts fail due to fatigue. These cars were never designed to last 50 years. Simply replace the failed dimmer switch with a quality replacement and it will likely last the lifetimes of the next two owners, especially if the car is relegated to weekend and summer use.
Thanks Joe. That's a project/upgrade that's on "the list," if you know what I mean.
Generally speaking I'm a big fan of your amazing Olds knowledge base. In the case of your response to me... not so much. So a dimmer switch failed and then what happened? In the words of the OP: "The switch had completely fried and melted part of the female wiring harness, as well."
My point with regards to relays on heavier amperage users like headlight circuits is that with a relay you only need one or two amps to switch it. That's one or two amps going through the dimmer switch. That one amp is not going to completely fry the switch and the female wiring harness and lead to the observed smell like melting solder.
To me its a matter of choices. The OP chose to go back to original tech and the possibility of the same outcome along with the adrenaline rush that comes from smelling an overheated circuit. You applaud that.
I would have chosen to put in a $4 relay with the result only 1 amp would be going through the dimmer switch out to the headlights and zero possibility of the excitement of overheated components between your hands.
Lots of folks don't know about the benefits of switching with relays so I thought I would put it out there. Clearly what I consider an upgrade doesn't meet your approval so you suggest I am "adding several new and exciting failure modes..." The hyperbole of that statement aside, It seems we will continue to disagree on this point.
Jerry
Lots of folks don't know about the benefits of switching with relays so I thought I would put it out there. Clearly what I consider an upgrade doesn't meet your approval so you suggest I am "adding several new and exciting failure modes..." The hyperbole of that statement aside, It seems we will continue to disagree on this point.
Jerry
There's plenty of hyperbole to go around, like the statment that this simply needs a "$4 relay". A quick glance at the wiring diagram shows that TWO relays are needed, one for high beams and one for low. And since the brown and green wires from the dimmer switch would now control the relay coils, you also need to run a high current feed wire from the battery or horn relay to these new headlight relays to actually power the lights. To avoid repeating the potential problem, this power feed needs overcurrent protection. Priced a maxi-fuse and holder at NAPA recently? And since the whole point of this exercise is to carry the high current to the headlights, do you REALLY want to trust that to a $4 Chinesium relay? Price out Bosch, or better yet the Delco sealed weatherpack relays and matching sockets. This $4 fix is now $50 and a Saturday to install. And since a surprising number of car guys run screaming like little girls when electrons are mentioned (and may not even know which end of a soldering iron to hold), chances are this wiring mod will be implemented with poorly-crimped butt connectors, thus my "new failure modes".
I do agree that if the dimmer switch problem had been due to burned contacts, this would mitigate that. If, however, the more likely failure of mechanical fatigue occurred, then the result would have been the same, relays or no. The fatigue failure is due to number of cycles, not current handling, and would occur even if NO current were passing through the switch. Once conductive debris is loose inside the switch, Murphy guarantees that it will short from the case to the feed wire from the headlight switch. At that point, relays or not, the short draws as much current as the circuit breaker in the headlight switch allows it to. The relays only help here if you have also taken advantage of the lower current through the dimmer and also added a small fuse between the dimmer switch and the headlight switch. Of course, this means that in addition to wiring under the hood, one needs to also crawl up under the dash for more wiring mods...
I'm an aerospace engineer, and we perform failure modes and effects analyses all the time. Most important in that is ensuring that ALL failure modes are identified and likelihood and consequence of each determined. In this case, the likelihood of the failure being repeated in a brand new dimmer switch is extremely low for the next 40-50 years. If adding the relays helps you sleep at night, have at it. On my personal list of things to worry about on the car, a dimmer switch failure that is unlikely in the next 50 years doesn't even crack the top 100 items.
There are three [er..four, ...ummm... five....] reasons why we add extra stuff to a car that is already working just fine:
1.) To make it do something it didn't do before.
2.) To make it do something better than it did before.
3.) To make it more reliable in doing something it already does.
4.) To return it to normal operation after general deterioration.
5.) Just because we like messing around with it.
In this case, we are talking about the third thing.
The vast majority of factory parts on these cars are well designed for normal use, and do not need to be "upgraded" to improve their reliability.
These include the headlight, signal light, and windshield wiper switches.
The convertible top switch is a conspicuous outlier here - its mechanism is entirely adequate for other jobs it performs, such as operating the tailgate power window, but is simply not designed to withstand the current of the top motor over an extended period of time.
The average user will obtain no reliability benefit from swapping in relays for the headlight switch, but will definitely benefit from swapping in relays for the convertible top switch (and also the poorly-designed convertible top relay in the '71-on B-bodies).
That being said, there are two other cases in which added relays would likely produce a benefit: Numbers 2 and 4 above.
For Number 4: Depending on climate, storage, and use throughout its life, some of our cars will have more or less corrosion at electrical terminals throughout the electrical system.
Splices in the wiring harnesses were soldered, but wire ends were almost all merely crimped, and connectors were not weather-proofed as they are on modern cars.
In addition, the fuseblock terminals are thinly plated steel, which tends to rust.
Each of these connections can add a small amount of resistance, which can add up to several ohms, enough to decrease the voltage at the endpoint by a volt or even two, which is enough to significantly impair function, even if you have obsessively cleaned your grounds. Obviously, according to Ohm's Law, the voltage delivered will be most affected in high-current circuits.
Because of this, certain people with certain cars may find that their headlights are too dim, or that their starter solenoid doesn't want to pull in enough to engage the starter.
In these cases, on these particular cars, these people will benefit from adding relays to provide a direct high-current path, rather than spending a whole lot of time and money rewiring their cars.
Finally, we have case Number 2, where you want to make something, such as your headlights, better than it was when the car left the factory.
If you want to add headlights that draw significantly more than the originals did (I have 130W high beams on one of my cars), then you will benefit by adding relays (and heavy wiring) to handle a current load that your electrical system was never designed for.
Other than that, I of course agree with Joe's detailed and clear discussion of dimmer switch failure.
There's always a way to get several pages out of a topic.
Eileen towards the fewer components = fewer fail points methods.
I have seen yellow crimp-ons placed on 18g wire too.
Household switch in the car to operate the blower, er, noisemaker.
Not everyone is real good at installing electrical things.
1. It does take two relays for headlights. My oversight.
2. Factory sealed relays like GM weatherheads and some Ford relays are better and I make it a point to buy all I can lay my hands on at the pik n' pull where they charge me about $2 ea. I don't worry about failure on used factory relays.
I'm not understanding why a NAPA maxi fuse is required. I typically use auto resetting 20-30 amp breakers available almost everywhere from $7 to $12 or so. I'm aware that breakers are not considered as precise as the range at which they trip may not be as tight as a fuse.
I always, always avoid crimping and go for solder on terminals and cover them with heat shrink. My attempt to do a 'best practice'.
I just want to add that Eric's review of why we add extra things was spot on. I am guilty of 2, 3 and 5.
2. Factory sealed relays like GM weatherheads and some Ford relays are better and I make it a point to buy all I can lay my hands on at the pik n' pull where they charge me about $2 ea. I don't worry about failure on used factory relays.
Just out of curiosity, why are you worried about the current carrying capacity of a used factory dimmer switch, designed and tested for this application, but not the similar failure probability of a used factory relay?
I always, always avoid crimping and go for solder on terminals and cover them with heat shrink. My attempt to do a 'best practice'.
As do I, but nearly every electrical thread on every automotive forum I've ever read contains the words "...wiring is not my strong suit..." or something similar. There's a reason why just about every used vehicle I ever buy has a handful of those stupid Scotch-Loc connectors in it.
I just want to add that Eric's review of why we add extra things was spot on. I am guilty of 2, 3 and 5.
[QUOTE=joe_padavano;920457]Just out of curiosity, why are you worried about the current carrying capacity of a used factory dimmer switch, designed and tested for this application, but not the similar failure probability of a used factory relay?
__________________________________________________ ___
Probably because the rated life cycle of a cheap tyco/bosch 12v 30 amp relay used in lamp service is one quarter million cycles. A GM weatherhead would likely be higher. (I want to believe GM wouldn't put cheap crap, low-bidder stuff in their cars) If you use your flasher actuated by a relay ten times a day 300 days a year that's 3,000 flashes/yr. Which is 83 years of service for the Tyco and maybe 100 years for the GM? Most cars wind up in pik n' pull lots from accidents before they are well and truly used up but even if they've made it 20 years there is still 80% of the life left in their weather sealed relays. For the record I only experienced one modern relay failure and that was at installation. The old metal cased horn relays are another story.
To restate: I just think its a good idea to put the lowest current that will do the job through anything electrical in the passenger compartment.
Your idea of an extra fuse was a good one. It would prevent smells like melting solder. In turn that prevents conversations like "Dear what smells hot in the car? Is something burning? I think we'd better pull over. Do we have a fire extinguisher in the car? Well why not? I think we need a new car!"
Thanks for asking the question. It made me do some homework. I was surprised at the life cycle ratings of relays. Sturdy little buggers.
Jerry
Last edited by 47 Convertible; May 16th, 2016 at 11:13 PM.
Reason: excess verbiage not to the point of the answer.
Your idea of an extra fuse was a good one. It would prevent smells like melting solder.
Joe's idea of a separate, lower-value, fuse in the control circuit is not just a good idea; it is essential for your argument to be effective.
If the suggested control circuit is left with its inherent current protection (the magnetic circuit breaker in the headlight switch), then it will pass about 20A before the circuit breaker is activated.
This is definitely enough to create a hot spark that can create bad smells, generate heat that will melt plastic parts, and potentially start a fire.
Within the high-beam switch, there are three possible places for current from the 20A-limited +12V source to go: Through the low-beam circuit to ground (about 8A), through the high-beam circuit to ground (about 16A), or directly to ground through the metal switch case (whatever current the breaker will permit, presumably about 20A).
Since the switch contacts are designed to pass the specified current without damage, these two places will not cause smoke, sparking, or excess heat, even if the switch mechanically jams in one of these positions.
The failure mode of concern is one in which internal mechanical failure results in the feed contact connecting with the switch case and ground. In this case, smoke, heat, sparks, and potentially fire will be generated REGARDLESS of whether one uses a relay or not, UNLESS one also fuses the wire from the headlight switch at a current consistent with the trigger current of the relay (usually 250-500mA), so the initial statement that using a relay would have prevented this problem is factually incorrect without the all-important inclusion of additional current limiting to the control circuit.
And all of this to prevent a problem (overheating of the high-beam switch after a mechanical failure) that is highly unusual in the first place.
There are 2 types of engineers. (and people) Those that think and try to prevent all possibilities of failure, and those that simplify and try to to prevent likely possibilities of failure. I am not an engineer but have worked with both types. Personally, I am a KISS kind of guy. Fuses were adequate, but fusable links, breakers, then relays came along and did improve things. Just made it more confusing at times.
How long can this thread go?
I'm in the same camp as Joe, the switch has been in the car for 47 years before it failed. Another switch will likely outlast the car and possibly the current owner. Why reengineer other components that are subject to premature failure in less time than the lifespan of the original swirtch?
Hi all. I would first like to say I love this forum. I have been working on a 70 cutlass for a while now. I have come here a few times to figure out some stuff and things along the way. Thanks for all your help. I wasnt sure if I should start a new thread as I am having the same issue. I have chuckled a few times going through this but I have a doozy. This is what I have and this is what I have done.
1970 CS 350/th350 stock interior minus the radio and added speakers, dome light and sail panel lights. All harness in dash are og. Everything was green with wood grain and I changed it to black with wood grain. Which means I pulled the dash pad. I believe I have everything hooked up correctly.
Engine mods: overhaul, changed to flat head pistons, comp cam, holley efi master kit, hei distributor, swapped externally regulated alternator to internally regulated, and headman headers. Yall probably dont need to know all that but just in case...there it is.
The issue is headlights were not coming on at all. I started at the floor switch because when I replaced the carpet from green to black, I noticed some burned plastic on the 12v feed (blue wire). When i pulled the connector the plastic had deteriorated and all spades were touching in some way. I hooked up my power probe and pulled out wiring diagram.
i unhooked the floor switch and took out all spades so they werent touching. I then pulled the headlight switch **** and probed for voltage on the blue wire got nothing. I shot 12 volts through the green wire at floor switch and all lights came on. I shot 12 volts through brown and nothing. The main light switch was functioning everywhere but to the floor switch so bought a new floor switch (no clicky clicky on the original floor switchy switchy also if failed a continuity test) and main switch. I replaced the dash switch first. Doing this opened the voltage back up to the blue wire. I installed new floor switch and tested. I got high beams only when depressing the floor switch.
okay so at this point, I at least have high beams and know all the wagner basic high beam and low beam bulbs will come on at least with the new switches, but only in high beam mode)
Knowing that parts arent made like they used to be and its possible to get a new faulty part, I took both switches back for another round and am still having the same problem.
So now what??
Both switches are value craft brand from AZ. So am I just getting craptastic parts or what am I missing here??? Also everything else on the car works as far as lighting and the dash is concerned. I also tested for continuity on low beam (brown) wire from floor switch to headlight and its good. Again they come on in high beam mode sooo... Before After After
I am getting battery power to the blue wire on floor switch.
If all the headlights will come on in high beam phase then that means low beams operate, just not at the floor switch?? Tis a doozy for me....
I think my next step will be to overlay the low beam wire from the floor switch to the low beam light and see but I want to see if the gurus have anything I might be missing first. 2 bad parts in a row seems unlikely but not unheard of...which is sad really.
anywho, any takers on this conundrum??
I am getting battery power to the blue wire on floor switch.
So you are saying that when you pull the headlight **** all the way out, you DO get power on the blue wire at the dimmer switch? Are you using a test light or a Harbor Freight voltmeter? The HF tester is low impedance so it will sense voltage but not current. A test light puts enough of a draw on the circuit to tell you if there is a loose or dirty connection that can show voltage without load but not carry the current of the bulbs.
If all the headlights will come on in high beam phase then that means low beams operate,
Again, no. The high beam filaments are completely different from the low beam filaments. Think of it as TWO COMPLETELY SEPARATE BULBS in one housing. I don't know why people have so much trouble wrapping their heads around this.
May 14th, 2016, 08:08 AM
