Hi Susan
The old Märklin solenoid accessories do not need ANY oil except a tiny drop in the rods and levers on semaphores.
The inside of the sonénoid is made of a metallic guide (nickelled "U"-shaped guide) in which a nylon core slides.
So any oil residue may bring friction rather than any good.
Usually, when there are operation issues on these, they are cause by previous overheating of the solenoid which causes the inside guide (the U-shaped one and the last top of the U to become narrower and bring friction.
Alas for these there is little you can do. Avoid overheating

Jean

When cleaning electrical/electronic contacts and parts with plastic, use the plastic safe Deoxit spray-lube. Available from Amazon, etc.

Hi Susan,
I'll second the reference to Martin's video; the solenoids are essentially the same on turnouts and signals so cleaning the inner parts can improve both. Both are somewhat fragile but with care can be disassembled, cleaned and reassembled (take care to not break wires' connections!). I'll also second the use of a residue-free electrical cleaner such as CRC. Avoid any that have a lubricating additive imo because it will eventually dry out and/or attract dirt. I've cleaned many of the 5202 and similar turnouts, and many of the old analog signals with great success as long as they haven't overheated and warped. I never lubricate the sliders with anything after cleaning.

Martin doesn't cover the signals, so assuring the cleanliness of the contacts on the slider for using the block controls of the signals is also critical (they're on the exposed end of the slider). After cleaning with CRC, I give them a gentle rub or scrape to remove oxidation on the contacts. I also (reluctantly) give them a gentle reshape if they don't maintain contact properly. Sometimes it takes some trial and error to get it right; a multimeter to check electrical continuity is a big help before reassembly! I use the signals for analog block control of the center rail and the catenary with great results.

I hope this helps. Good luck!
Brian

I used 'sledgehammer' approach on about 80 solenoid M switches and vintage signals (they got wet/damp). Sprayed WD40 inside solenoid sleeve instead of taking unit apart. Used paper towel to removed excess. All work well again, incl multi-solenoid (2 arm) signals. No residue issues.
I also tested silicone spray, but with limited success.
First try on one unit to test impact.
Ben

"If I move that lever out of the way then the slider travels the full distance but with the lever in place the travel is restricted." So the double solenoid is good. Congrats!

As a temporary "fix you could put a small drop of oil on the axle of the lever, work it a while, and then see if the slider travels full length with the lever engaged. That would at least show if the lever is aligned correctly. Then when you get a contact cleaner you can clean all the old gunk and the new lubricant out of the lever's axle and it "should" work like new.

If the oil didn't help, then carefully looking for ways to realign the lever might work.

Hello Susan,
The 7188 is about the easiest signal to rebuild. How many volts a.c. are you using to test? Are you using a.c.?
With LOTS of patients they can be tuned to work @ 12vac.
Some tips:
Remove the plastic plunger from the coils. Clean all gook with lighter fluid. Using a flat surface and #600 wet or dry hold the plunger against the paper and GO! Do both sides. Then go to #1000 and repeat. You will be able to observe high spots on the brass contact sheet which is crimped round the plunger. The smoother and flatter you can make the brass; the less resistance there will be when it drags across the sprung contacts. Before reassembly I like to "wax" the plunger using a minute touch of Dielectric Grease. Rub off all excess. It must be dry. It kind of works like Armorall on your motorcycle seat.

Mikey

Looks like you got the "lantern" on wrong. You gotta hook the little finger (opposite the screw side) into the square hole. Then, bring it down and pick up the solonoid rod. Then, put the screw. All this whilst keeping the bulb in the lantern assy. If it goes on real easy, You're probably doin' it wrong.

USE NO OIL

Mikey

@analogmike - thanks for pointing out my last assembly mistake. I've corrected it but the problem remains.
Also thanks - 'lantern' is a MUCH better term than 'knob'!
@kiwiAlan - I'll give that a try.
Susan

@analogmike - thank you once again.
(Side note: I love the way different countries use different names for the same thing: points - switches - turnouts (and probably others!!!). Go to love English!)