Can Convertible top motor windings be cleaned up and fixed? Or bin it?

[Jaymo]

Hi All

I have been flat out, the my work got bought out by one of the largest companies in the field, and I got smashed with integration… I haven’t been on here for about a year….my apologies.

I have managed to hang onto the car during the current cost of living crisis, drought, interest rates, blah blah….

Super time poor, I managed to get the car out a few times this (Aussie) summer. Until the roof stopped operating…. Stuck down (open) no sound whatsoever when I hit the button.

My car is 90’s RHD converted, so much of the electrics is non standard… I went exploring and found a 30 amp fuse nearly vaporized.

This fuse fed into a coil, coil holder fell apart….

Coil was OK though, triggered on 9v and gave continuity so I temporarily wired in a new base…

Hitting the button nothing…

I then thought I might bypass everything and use six meters of 50 amp wire plugged into the motor to close roof and work it out later… but nothing happened other than the free wire ends at the battery welding themselves to the battery post ( I am guessing short in motor)…

Is it worth trying to pull pump electric end apart (like a starter motor?) or don’t even try? I am time poor.

Also with a multimeter across the plug at motor I don’t seem to get voltage at the button… is there a fuse link in the middle somewhere?

Any advice appreciated!

Thanks!

[Jaymo]

Ok, I wanted to check the switch…. So I ripped the dash out…

The switch is good, I checked it with a multimeter for continuity when thrown in either direction. I saw the switch has an incoming feed then splits it straight to the red or yellow heavy gauge top motor wire… so I am puzzled by the solenoid because that is all upstream…

I could not see an in line fuse link on the incoming power, I took the instruments out to trace the wires as they ran behind

Currently stumped…. I will try and sleep on it… still wondering if it is worth attempting to clean out the armature on the motor… I am a “lapsed” mechanical engineer , not electrical ….

What am I looking for in ohms across the wires? Actually as I type it is not pos and neg… it is just pos and pos (one or the other) with the earth strap the neg?

Which means I shouldn’t get a reading by sticking multimeter into both plugs , I was looking for it is measured across one plug wire and earth….

[Royce]

If hooking power and ground up to the motor does not work it needs to be professionally rebuilt. Save yourself some time and swap the motor for either a new or rebuilt one.

[Calicat]

You are correct - there is an up winding and a down winding with a common ground through the strap. But if you are time poor, Royce is right.

[Jaymo]

Thanks, yes, looking that way… the problem is I can’t just dig one out from a wrecker here in Australia.

[Royce]

They are all over eBay here. Maybe you can have your original restored in Oz - I would look into that first.

[Jaymo]

Ok…. So I made some assumptions and made an ass of myself….

Fuse blew holder and relay base fell apart… I fixed that… motor still would not run (But did not blow new fuse).

I assumed the switch was double pole double throw Normally Open… push switch one way electrons flow down one of the two wires to the motor , then back to the switch down the other. Push the switch the other way same thing but polarity reversed.

When I measured resistance at motor (across both red & yellow wires). Short circuit.

I tested the switch, across the motor plug (expecting +12v and -12v) I got zero.

I figured the switch was bad, so I ripped out the entire dashboard… and found a perfectly good simple switch…

Realized that it is +12 down one wire, then earth strap off the motor… the other direction is 12v down other wire, then earth strap down to earth. Test wires for that … I have 12v at the plug if I earth to ground so power to the plug.

Checked resistance of either wire to earth at the motor (instead of across the wires) and I get normal and equal numbers …

I put everything together… still no go, silence… like the starter motor on my first car, a 1976 Mazda RX5… on average, every 10th start , silence, whack the starter with a wrench and it would kick over…

So I get a big wrench, and give my top motor a whack…hit the button… works perfectly

I ripped my car apart…. For no reason!!! It looks like this for nothing….

I fee like starting a DDDDSLID (Don’t Do Dis Dumb Shit Like I Did) thread!

[PonyCarMan]

@Jaymo

So I get a big wrench, and give my top motor a whack…hit the button… works perfectly

As a ME you know you’ll get another shot at diagnosing this. The good news is it is usually a brush that is sticking in the holder or is worn down far enough to make intermittent contact. At least you’re into a mechanical problem now. Oh, wait. On these cars they’re all mechanical problems.

As common as those motors are, there must be a rebuilder around you. And wait time shouldn’t be a problem since you’re 6 days from the official start of winter.

BTW, I’ve also done the overly complex diagnosis instead of starting with the simple stuff. When I should be checking the simple things first, I usually start by trying to rule out the ones that could be very difficult to find, replace, etc. Don’t the Aboriginal people have a saying for that? I think it goes “OHWA TABOO BIAM”.

Unfortunately, as our cars get older, we get more opportunities to experience this.

[70scj4spvert]

What happens in that situation is the brushes stick in their bore and don’t make good contact with the commutator. When you smack it with a hammer, you jolt it just enough to free up the brushes to make decent contact again and then boom, you’re back in operation. But then again, when you measure resistance thru the motor, you would normally get a low resistance because you are reading resistance through the windings.

[Calicat]

Yes, this is a 30 Amp motor, so winding resistance is less than 0.5 ohms. This makes it hard to measure the winding resistance accurately with a DVM because the resistance of the meter leads themselves is close to what you are trying to measure.

[Jaymo]

Yeah, I got .8 ohms on either polarity to earth …whereas plugging the multimeter across both yellow and red wires read like a short circuit .

I have closed my roof, I will investigate the motor later…. And report back ….

I have heaps of other tasks to do now that I have ripped the dash out…. Opportunity to run cables for stereo gear, and replace the dash lights (I will be posting a question on that topic)

As always, thanks everyone for your help. (Pause as I switch to other tasks)

[Calicat]

Sounds like the short could be between the red and yellow wires where they attach to the motor windings. You should see something closer to 1.6 ohms across red and yellow.

I keep putting off pulling my dash for that same reason - so many things to fix while I’m in there, it will put the car out of commission for awhile. Guess you are going into winter down there, so might as well make it count!

If your LED’s were a bit warmer (yellow) in color, the color would be more green. But I like the way yours look - except for the tach.