Landing & taxi light inop

A

allthesetouch&goesbutno

Filing Flight Plan
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allthesetouch&goesbutno
First off, I checked the bulbs, they both work hooked them up to a battery.
To set the background I just got hold of a Cessna 150k, when I bought it all lights were functional. When I went to test the lights (temperature 20F) I flipped the master did a walk around and all the lights went on except for the landing light, then after about 30 seconds it went on. Later on when I was taxiing in to get gas, landing and taxi lights went on immediately every time and worked flawlessly, I switched the landing light off and fueled up. Came back another day about a week later and the landing light did not come on during the initial walk around after leaving it on for a few minutes, it only went on after engine start, Its a 12/14 volt system.
Then shortly after that during taxi out, the landing light refused to come on altogether.
I decided to do some troubleshooting, found out no power was making it to the landing light but power was making it to the taxi light so it must've been something in the wiring, I went to check the switch (which didn't click on and off like all the others it just rolled smoothly) and I couldn't figure anything out but on the back of the switch I did notice that there were wires spliced around. The airplane documents doesn't have any updated wiring diagram. So I figured it was a switch issue or a diode or inline fuse and ill deal with that hassle soon.
Fast forward 2 months to summer I'm flying and the taxi light refuses to come on during flight or on the ground with the master on, checked the bulb with a battery and its fine so my conclusion is its a wiring issue, I'm very mechanically inclined but electronics is my weakness. Does anybody have any recommendations or suggestions or has seen an issue like this before? May seem a bit vague but I'm going to start tracing wires tomorrow that massive wire bundle behind the panel is still a mystery to me. Trying to do what I can before I drop it off with an A&P and have him work on it.
Any suggestions are appreciated!
 
It’s Summer, depending on expected night flying, maybe roll it into the next annual? Yes, look a little, maybe the switch is funky. If staying up late for night flying, yes, maybe the A&P is the answer.
 
Intermittent operation sounds like either a failing switch or a broken wire inside the insulation jacket. It is very common for wires to break from vibration just behind the spade lug where they attach to the lamp, especially if they have been improperly installed or repaired. It should be very easy to trace voltage at the switch and the lamp with a voltmeter. That will isolate the location of the problem.
 
Dirty switch. Spray plastic safe contact cleaner or replace (A&P).

Bad wiring (look for prior splices and a broken wire barely hanging on by the insulation). Test continuity. Replace splice (A&P) or wiring (A&P).

Corrosion on bulb receptacle or bulb contacts. Clean or replace bulb or receptacle (A&P).
 
Most common:

Bad switch. Their contacts oxidize and introduce resistance.

Bad fuseholder or breaker. Same oxidation.

Most likely: bad grounding at the lights. Seems to me that this model had the lights in the wing, and they were grounded at the spar. That connection gets oxidized or dirty or loose. Pay attention to the wire in the crimp terminals themselves, too; they oxidize inside the crimp. That goes for ALL crimp terminals at the lamps, the grounds, the fuseholder or breaker, and the switches, and it also applies to the Molex plug in the wing root where the fuselage wiring connects to the wing wiring. Sometimes it's obvious: green scum in there.

If the lights are in the cowling, the grounding is at the firewall. Trace the wires. Firewalls get dirty/oily/oxidized too, and vibration loosens stuff.

Sometimes one has to follow the circuit using a voltmeter. Master on, light switches on, and look for voltages between ground and the various terminals. Suppose you see 12V at the switch's output terminal but the light isn't on. Check the voltage on the end of the wire itself inside the crimp terminal. No voltage? Oxidized crimp. Easy. Continue through the system this way. Start at the fuseholder or breaker.

Sometimes you'll see 12V at the ground terminal itself, and you should not see it there. It's not grounding. If it's properly grounded, you'll see zero volts and the light will come on.
 
allthesetouch&goesbutno said:
I went to check the switch (which didn't click on and off like all the others it just rolled smoothly)
Click to expand...

This is a pretty telltale sign of the switch failure. Cessna has a service bulletin out for inspecting/replacing these switches. They are somewhat notorious for melting and failing (can look up numerous service difficulty reports on the switches w/FAA). And that soft feel is a pretty dead giveaway for having failed or nearly failed. In your 150K model, I believe you'd have the double switch for the landing/taxi lights which is S2160-4, which has been superseded to P/N TTGC-TA201-TW-B. The Service bulletin around these is : https://support.cessna.com/custsupt/contacts/pubs/ourpdf.pdf?as_id=27055
 
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Like to thank everyone for all the help!! On the taxi light, a quick switch replacement was the cure, and the connectors for the ground were extremely corroded on the landing light. (Relaying what the A&P told me), thanks again!
 
Like to thank everyone for all the help!! On the taxi light, a quick switch replacement was the cure, and the connectors for the ground were extremely corroded on the landing light. (Relaying what the A&P told me), thanks again!
 
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