Hello, I have a restored 68 with power top. When I had the top shop install the new top, they also replaced the rams, top motor and lines. Prior to body being completed and top installed, I disassembled, cleaned and lubricated all pivot points. Ever since completing the restoration I have been popping the fuse. My top switch also began giving me issues and I replaced it last year along with adding a circuit breaker in place of the fues. At the end of the season (last year), the new switch failed during the top down function. I figured the switch failed for sure but wanted to figure out why and suspected possible excessive heat (too high of an amperage) and finally got a chance to pop the switch out and take a look at it. The switch and even the connector show signs of excessive current so I put my lab scope and amp clamp on it an captured several waveforms (which look fine) but amperage was consistently at approximately 25 amps, with an initial peak at approximately 30 amps.
I am wondering whether anyone out there has, or could possibly, perform a current draw test on there motor and let me know what they come up with. I have taught and written material on current ramping of solenoids and motors and experienced enough to know only three factors really affect amperage draw (causing excessive amps)... Voltage supply higher than expected (mine is 12.6v KOEO and 14.7v KOER). The other factors are shorted motor windings (lower than normal resistance), or excessive mechanical resistance. Excessive mechanical resistance could be due to linkage binding or slower than expected motor armature speed (maybe someone can time there Top Up, Top Down speed beside performing an amp draw test).
Anyone who had similar issues or maybe even there own test results would be greatly appreciated. TIA

The top circuit is simple; a dedicated +12 through a breaker, to SPDT on-off-on switch to the motor/pump. (Although the breaker could be shared with power windows or power seat.)

You said you had fuses for the top originally? From the factory, there should have been a 30A self resetting circuit breaker on engine side of the firewall. Had a previous owner done some changes to the original circuits?

Did the '68 come with the power top from the factory? If a manual to power top conversion take place at some point, that might be a source of the mechanical resistance. The frames are different.

The power top switches are horrible. I've gone through several over the years on mine. The high draw, stresses the contacts, burning and pitting them. There is a discussion here about an owner adding a relay circuit to eliminate the high current on the switch. https://firstgenfirebird.org/forums/ubbthreads.php/ubb/showflat/Number/243940/Searchpage/3/Main/27731/Words/%22top+switch%22/Search/true/re-power-top-wiring.html#Post243940

I checked several of my documents and motor/pump vendors. Odd that nowhere can I find the current specs on the part. 12v seems to be stamped on it but no AMPS.

I have a 1968 convertible too. I have read lots of threads on here about the system and it's problems. The up/down switch seems to be the weak link in the system and requires replacement often. The above article is what convinced me to use relays. I have opened and cleaned my top motor and found the commutator to be very dirty and I polished it while it was apart. After that it worked much better. I also used new rams. I used the stock up/down switch to test the top and found my hinges were old, dirty and causing too much load. I oiled them all and after that the top moved smoothly. While bench testing the motor I found the load to quite high. The wires I was touching to the battery made a big spark when connected. I did not measure the amps but I would guess the load was sizeable. What I am doing is using high amp relays to operate the top motor just like in the above article. By wiring in some relays back at the motor, and using 10 gauge wires to power them, the load on the switch becomes very low as all it is doing is powering the relays. I also read about DC switches and why they are different from AC switches. A very high amperage load can actually cause the contacts to weld together. For that reason DC switches are built much differently than AC switches. I also found a DC switch rated at 50 amps and is a mom on- off- mom on three position toggle switch I can use in place of the stock switch if it still fails. I am also putting in a power seat so it will also use the 10 gauge line for power. So rather than worry about the stock switch burning out why not just use the relays?

Thanks for the reply Jimc2002.
This is an original 50k convertible with pwr top, windows, etc. The wiring for the top, and actually the pwr windows too, are connected via the fuse block and then run through the 30 amp circuit breaker to the battery. All of the harnesses and even the fuse panel are new from American Auto Wire. I do have the circuit breaker under the hood and it is also a new 30 amp. My issue is the high current on that pwr top circuit which was popping fuse (until put a breaker in place) and burning out switches. I really wanted to determine what normal convertible top Up/Down time is and/or normal current draw on that circuit.

Thanks, I was considering removing the load from that circuit and running a switched relay, but found it hard to believe this vehicle had an issue with too much current flow on that circuit back in the day.
You don't happen to have some times on how long it takes for your pwr top to go up or down do you?
I know that time (or the speed of the motor) directly influences current flow... The faster the motor turns (true for any motor), the less time the current flow has to build and therefore the less amperage observed. That is why I am taking note about how my top up and down speed seem to be slower than expected and wondering if the motor is wrong for the given application or the motor bushings are dry and dragging.
Note that if I had a bad connection (decreased voltage supply at the motor itself or ground), then current would be proportionately lower, but speed would still be affected.
I captured the current ramp waveform from the motor and seeing ~40+ amps when the motor just starts turning and then it tapers down to about 25-30 amps, but the top and down speed are slower than I expect (might just be me being optimistic).

I have not run mine yet this season yet but could wake it up and time the top operation if you want. This video shows an owner operating his. I believe mine works pretty much at the same speed as his. I also believe mine runs slightly better with the higher voltage of the engine running but works fine either way.
https://www.youtube.com/watch?v=MX5oCPrrjgY

Thanks, looks like he averaged 12-13 secs up or down time with the top. I just timed mine (KOEO - like his) and mine averaged 23 seconds in either direction... almost double the amount of time. I wonder if there are different motors for different GM bodies and top installed installed an incorrect motor/pump assy.

Here's another and it's about 23 seconds. It doesn't seem too slow.
https://www.youtube.com/watch?v=Ieo5PAFyfd0

I have probably put mine down hundreds of times over 54 years and not paid that much attention to the actual speed. Partially because I pause it part way down to fold back the flaps and close the clamps so the boot fits. And about several inches from all the way up to open the hold down clamps.

Thanks, I do the same when I put down my top. I found another video with up and down speeds around 15 secs. I pulled my back seat out the other day and checked supply voltage at the motor and grounds. The supply voltage looked good and I saw about 200mv voltage drop on the ground side, which isn't terrible for a motor pulling that type of amperage. I also noticed the ground on the back of the motor was a little loose but not causing a problem. Either way, decreased voltage would equate to less amperage, so that would not cause my issue. I think next thing I am going to have to do is disconnect the rams and see what current flow is, then ensure the top goes up and down relatively easy by hand. I have been checking pivot points and all are able to rotate so far with no substantial effort. Next steps would be to check the motor and make sure the motor isn't dragging due to a dry bushing. The motor is definitely new looking so I'm not really expecting to find any issues there either. I am also going to see if I can find a part number. One other thought is that these replacement motors are cheap replacements and maybe the company that built them tried to cut cost and chose a motor armature with less copper windings then OE. Less windings would equate to higher motor amperage too.

Here is mine in action. Timing it by the YouTube timer at the bottom it looks like 15 seconds. This is with new Chinesium rams, lubricated pivot points, and a cleaned and rebuilt motor. The ground is very important so maybe clean and re-secure that. I also had ATF leaking into my motor housing so cleaning was mandatory. When I was searching for a new motor I noticed that they all looked pretty much the same. At 3-400 dollars I decided to just take mine apart and clean it. There is a tiny O-ring seal that separates the oil reservoir from the motor and that was the culprit. I feel mine is noisier than it should be. 1968 Convertible top

That's about as long as mine takes.

Thanks, to me it looks like all of the OE pumps are coming in around the 15 sec mark. All of my wiring, hardware, linkage, etc are either new or rebuilt. I found a used OE motor on ebay, albeit I found the pump gear frozen and rusty when I disassembled it. My hope is to rebuild an OE pump/motor and install it and run the same test via my lab scope and time it also and see it that made a difference. If I disassemble the new pump I will also be able to tell if the skimped on the motor winding count or if something else is significantly different. It stinks because my intention was never to relinquish my OE motor when the top shop installed it. I expected to get it back since, IMO, it worked fine...just the lines and ram really needed a replacing.

I rebuilt my pump and I am an idiot. So go ahead and have at it. There are plenty of videos about this but I used this guy's YouTube post. Pump rebuild videoThe only hard part is fabricating two clips to hold the brushes away while you drop the armature back in. He used paper clips, I used baling wire. Be sure to mark the parts for re-orientation later. Very important!!! I also cleaned up the commutator which was very dirty. The small O-ring that separates the reservoir from the motor leaked, contaminating the entire motor. Also be careful not to misplace the little tiny balls and clean the cavity well. The pump rebuild kit that is available from many places contains two new balls and all the O-rings, seals, along with a new reservoir plug. Mine even had three new rubber mounting feet. Pump rebuild kit

Not sure why you would say you are an idiot
I got lucky and was able to return that used rusted out pump and just ordered another one from a buick convertible (part numbers appear the same along with design... even noticed the same delco pump used on some Ford and Dodge products). I already purchased a rebuild kit and going to see if this one works out and then test the motor and timing for comparison.

If you knew me better you would understand. Do you have the 1968 Fischer Body manual? The rebuild procedure is in that book along with some important pictures. But I found that YouTube video to be even more helpful. That manual also has a ton of information regarding the convertible top, with troubleshooting and adjustment procedures.

I am happy to report that I resolved the issue and my top motor now only pulls approximately 20 amps and top up or down speed is less than 16 seconds with KOEO. I tried looking for a used OE pump / motor which was less than $100, but ended up finding a new (aftermarket) convertible top motor/pump on line for $160 (quality appears to be very good). I went that route after purchasing two used pumps which were not even close to being rebuildable (extensive rust/moisture damage). Thanks to all of your help in info and items to look at or try... much appreciated!

So the conclusion is that the shop used a cheapola pump causing the excessive current draw? That figures because every shop I know of bills you the most for the cheapest part they can find. I'm glad the new better quality pump solved the problem. I am at the stage of wiring up the system for the top and the power seat. So if normal operating amperage is 20, the factory used a 30 amp breaker, would I be prudent in using a 40 amp waterproof marine grade breaker on the engine side near the battery on a dedicated feed line? I am making an 8 gauge feeder from the battery into the passenger compartment, which will split into two 10 gauge lines, and serve the top and seat with their own 30 amp breakers. I will also be using a dedicated ground wire because I don't trust 55 year old sheet metal. I don't intend to operate the seat and top at the same time, but things happen. I figured a 40 amp breaker would handle the 30 amp loads without tripping, yet trip quickly if necessary. I am still using the relay system to take the load off the dash switch. But I also intend to mount a separate switch back near the pump. I found a 50 amp DC switch that I can use as an emergency switch or for troubleshooting. Plus being 50 amp DC specific, I can bypass the relays and power the top with raw voltage from the feeder lines. That way even if my relays fail I can still get the top to work. But the most important information was that when the motor dragged, amperage went up to almost 40 amps. That would trip the 30 amp breaker and maybe even the 40 amp unit. That points to the necessity of maintaining the motor/pump, and being cognizant of any laboring or slowing down. If it stays as warm this winter as it did last year this should be do-able.