A few weeks ago, I received another 7002T, also new-in-box. But this one is a first-generation 7002T since it has the open grille. And it was manufactured in 1981. I was excited about it because the 1st gen 7000 series horn/strobes are especially hard to come across . But when I tried to set it off using 3 9-volt batteries, it would not sound at all. Perhaps something clicked.
I’ve noticed that the open-grille 7002Ts have four screws (two per terminal) while most models with the tamper-proof grille just have one screw in each terminal. And then I saw someone wiring up a 7002T-12 from 1986, he screwed in four wires into the terminals (two red and two blue). Is that how the older 7002Ts are supposed to be wired up? I put a red positive wire into the bottom terminal, and then screwed in a black negative wire in the terminal above; but the horn would not sound.
The device came with an instruction manual, and it said to use blue for positive and white for negative for the strobe; that kinda confused me because I thought that would only apply to the 4-wire version (34T-WS).
So here are two photos. The first one is the back of the device. Second is how I wired it (black wire in the top terminal block, and red at the bottom where it says “+”).
Since I didn’t take a photo of my 7002T wired up, here is a much higher resolution of the back of the unit. And I did a photoshop of how I wired the device. Black wire in the top terminal, and red in the bottom terminal.
I wonder if you need four wires because each terminal block has two screws, even though the horn and strobe are wired in series. Or are the extra sets of screws just a back up in case one screw is lost? The later model 7002Ts (closed grille version) usually have just one screw in each terminal block, and the screws don’t come out that easily.
Also, the installation manual said that the horn leads are red and black while the strobe leads are white and blue. I didn’t think you would need white and blue wires for a 7002T because of how the horn and strobe are wired. But I do recall seeing a tutorial on YouTube somewhere on how to wire a 7002T that has 2 screws in each terminal block, and the person did have to put in four wires into the terminals.
The two sets of screws are there for the INCOMMING and OUTGOING circuits or to attach the EOL resistor. Most likely your 9 volt battery arrangement doesn’t have enough power to drive the horn and strobe, or at least not for long. Did you try reversing polarity?
I also tried putting two positive wires in the front screws and two negative wires in the back screws, didn’t go off. And I even tried two negative wires in the front screws and two positives in the back, same thing. Then i tried two positive wires on the bottom terminal and then two negatives on the top terminal.
Also I saw videos of another enthusiast powering his early closed-grille 7002T. It had the same sets of screws as the open-grille models. But he only put wires in the front screws (positive on bottom, negative on top), powered the device from 3 9-v batteries, and the device sounded. So I think my open-grille 7002T came DOA.
t ain’t my intent to flog a dead horse but have you tried measuring the continuity of the coil, directly on the solder joints where the coil is connected, just so to rule out if the coil is blown or not? (I unfortunately don’t have a [yet] 7002T that I can get readings from for you to check against).
If it’s not open and you got some continuity out of it, the fault has to be elsewhere, a broken wire, a bad solder joint, or something else. Personally, I don’t think a bad strobe would cause the horn not to fire at all, but given they’re wired in series, it seems to be a plausible explanation too.
It’s a real pity that this one arrived DOA, not only open-grille 7002Ts are rare. I had no idea they even existed in the first place, I always thought that 7002Ts all had the later “vandal-proof” grille and 7002s had the older fully open design, irregardless if they had screw terminals or not.
Plus that one looks like it was just pulled out of the box…
I’ll go and still get the readings off my 2nd gen 7002T-24’s coil (mfg circa 1991…
I don’t have a good multimeter so my readings might be false. All of them were done on 2K caliber (as that’s all my crappy multimeter has), I’ll just write what it displays:
Across coil: .41
Across terminals: .605
I’ll try with my other DMM if I can get it to work…
The real difference between the two series is that the 7002 has pigtail connectors and the 7002T has screw terminals (the “T” actually means terminals). In fact, both series came out at the same time, with an open grille. It’s just that back then, the terminal models weren’t as common, but then became the only option available shortly after the grille was redesigned, which is why you most often see 7002s with an open grille and 7002Ts with a closed grille.
t ain’t my intent to flog a dead horse but have you tried measuring the continuity of the coil, directly on the solder joints where the coil is connected, just so to rule out if the coil is blown or not? (I unfortunately don’t have a [yet] 7002T that I can get readings from for you to check against).
