73 convertible top problem

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bailer01

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Just started happening with my top. Whether it's up or down, if I go to put the top up, the motor will run for a few seconds, top moves then nothing. No motor sound and no movement. after a few seconds I will hit the switch again and motor runs and top moves, but then stops. Is this a relay issue?
 
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I don't believe there is a relay but there is a circuit breaker usually mounted on the starter solenoid. Check all connections for corrosion and make sure everything is tight.
 

SVGAL42

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I don't believe there is a relay but there is a circuit breaker usually mounted on the starter solenoid. Check all connections for corrosion and make sure everything is tight.
It does sound like the relay, as Tommy has said. I had a similar issue with top and power windows stopping and then after a short while working again for a short time. They are both on the same relay and that is an easy and inexpensive fix.
 

bailer01

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Thank you everyone! Will check that out
 
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Stock 1973 Mustang Convertible with a 351C 2v and C6
Modified 1970 Mach 1 M-Code with a 351C 4v Manual

Just started happening with my top. Whether it's up or down, if I go to put the top up, the motor will run for a few seconds, top moves then nothing. No motor sound and no movement. after a few seconds I will hit the switch again and motor runs and top moves, but then stops. Is this a relay issue?
If you have not done so, check your fluid level. If it is low the pump may working too hard and tripping the circuit breaker on the black yellow dot accessory wire near the solenoid.
 
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From your description the electric motor brushes sound like they are nearly worn out. But, the convertible top motor is not something I would expect to have been used so much that the brushes would have worn out "already," as compared to brushes in the alternator or starter motor - even the windshield wiper motor or windshield washer motor. But, these are complex machines, and anything is possible. Before chasing down a new motor I think it is worth looking at the entire circuitry for the power top system.

Attached is a snippet from the 1973 Mustang schematic I have, with a correction (actually, one of several minor corrections throughout the master schematic file). The schematic shows Fuse #2 is used for the convertible top switch, but that is not what is really going on. Yep, that's right, the schematic is wrong when they cover the Fuse Block section in the schematic (page 1 of the PDF snippet file).

I have annotated the schematic file that is attached to this comment to reflect how the circuit is really set up. As mentioned elsewhere in this thread, there is a circuit breaker coming off the positive cable terminal side of the Starter Relay that feeds the convertible top switch directly. The Circuit Breaker feeds Circuit 175 (Black with Yellow Dot) that then feeds the convertible top switch directly (no relays), and provides power for the optional engine compartment light's mercury on/off switch. No relay for the convertible top is shown in the schematics, and I have never seen a relay for one. The relays I have seen in the 71-73 Mustangs are for the seat back latch actuators (solenoids), the starter, power back-lite, headlight on warning, and power windows. See the right lower section of Page 1 of the file named "1973Mustang_ConvertibleTopCircuitry_20220123.pdf" attached to this message. I hope the schematic helps you out.

I find a lot of intermittent and unusual behaviors are caused by loose or poor grounds. There is a Ground #803 in the schematic, which is shown in both of the last two pages of schematic drawings, but on the last page of the schematic diagrams are drawn details are given re: where Ground #803 is located, along with 3 connector locations and connector drawings (lower right quadrant of the last schematic page in the attached file). I have highlighted those areas with a red box outlining them. Every one of those connections, and the ground, need to be checked before trying to locate a switch and/or motor for replacement, in my humble opinion.

To make things even more complicated, another enthusiast reported to me his convertible top stopped working until he replaced Fuse #4. I recorded that having been reported in the next-to-the-last page in the attached PDF file, but can't make any sense of why that might have happened as Fuse #4 controls no circuits related to the convertible top (see top left of Page 1, and schematic grid location B31 in the attached file). But, I recorded it anyway in case there is a variant wiring not included in the schematic files I have. I am thinking this Car Season I am going to pull Fuse #4 in our 73 Mustang Convertible to see if it impacts our convertible top power or not. I am both betting, and hoping, it does not impact it.
 

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It does sound like the relay, as Tommy has said. I had a similar issue with top and power windows stopping and then after a short while working again for a short time. They are both on the same relay and that is an easy and inexpensive fix.
If you have found a relay (not the circuit breaker off the starter solenoid) I would like to get a photo of it and its location so I can annotate that on my schematics. Thank you.

An aside, I have never seen a relay for the convertible top circuit, including on out 73 vert Mustang. But, it is possible that circuitry may have had a mid-year change not reflected in the generally available schematics. I have seen worse mid-year wiring changes over the years. Always so much fun to track those down...
 

SVGAL42

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If you have found a relay (not the circuit breaker off the starter solenoid) I would like to get a photo of it and its location so I can annotate that on my schematics. Thank you.

An aside, I have never seen a relay for the convertible top circuit, including on out 73 vert Mustang. But, it is possible that circuitry may have had a mid-year change not reflected in the generally available schematics. I have seen worse mid-year wiring changes over the years. Always so much fun to track those down...
My misuse of words~ I did mean circuit breaker, not relay. So sorry.
 
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I would check the ground. I had a similar problem. Cheap and easy fix if it is the problem. The ground wire runs right from the motor. Mine was attached to the trunk divider.
 
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My misuse of words~ I did mean circuit breaker, not relay. So sorry.
Gotcha re: Circuit Breaker meant, not Relay. An easy point of confounding to hit. Okay, I can breath easier now. I am, frankly, surprised a relay was not used to keep minimal current from having to traverse the switch contacts. I guess somebody opted to save 25 cents in the cost of assembly.

An aside, if you ever need a wiring schematic, or engine vacuum schematics, my Go To is Forel Publications at the link below. The 1971 and earlier wiring schematics are a bit sparse (from Ford), but better than nothing. The 1972 electrical schematics are much better, and 1973 is really good. That said, I have found a few minor errors that I have annotated on my 1973 schematic file copy. Nothing earth shattering, but worth noting, I think. Also, the 1973 schematics are very close to the 71-72 wiring, with only a few (also) minor differences. If you need 71 or 72, get it, but get the 73 also.

As for vacuum schematics for the engine, the 1973 ShopManual Volume 6 has (finally) some really good info and schematics of many engine calibrations. Luckily many of the schematics, excluding the EGR systems, apply to 71 and 72. Plus Mustang Barn provides the schematics for 67-72 for no fee. With their permission I consolidated their PDF files into a single PDG grouped by year and sorted by engine. It is attached to this post. Feel free to share it on a no fee basis as you see fit.

 

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