Replacement Battery Cables for 84/85 RX-7s

This document last modified August 22, 2003.
Much has been written about the troublesome battery cables that are on first generation RX-7s. Perhaps the best description of the problem that I've ever seen is David Lane's write up at http://www.nellump.net/peri/epi/gen7Techs/starters.html. I'd strongly suggest reading it when you have the time. But I'll offer an executive summary right here: the battery cables on our 18+ year old cars are subject to internal corrosion such that, eventually, they can't carry the amperage that the starting, ignition and accessory electrical systems need to function properly. The result is one or more of the following symptoms: difficult starting, where the engine turns but won't fire; frequent flooding as a result of either slow cranking or a weak ignition system or both; low voltage displayed on the dash meter; excessive dimming of the headlights or interior lights or slow power window cranking, particularly at idle; even a somewhat "less than lively engine" (slightly low on power), again, as a result of an ignition system that isn't getting a full supply of electrons to work with. The cables may test fine with an ohm meter, but that only tells you that there is at least one strand of wire left within the cable that can carry electricity from one end to the other. The ohm meter won't tell you whether or not the cable can successfully carry the full amperage required to power the starter or any of the other systems that I mentioned earlier.

Explaining all of these symptoms is not the purpose of this page. Handing you a quick and easy solution is. Therefore, I took it upon myself to record some part numbers for the Exide battery cables that I have used on three GSL-SEs and a friend has used on a fourth. I know that they fit, and I know that they require a minimum of technical skills to properly wire them up. (You will need to be able to splice wires together to connect the fusible link lead to the new battery cable.) I'll mention here that many shade tree mechanics choose to purchase "car stereo installer type" gold plated terminal cables, and I do consider them to be an excellent solution for anyone planning to install aftermarket electrical accessories like a gigawatt stereo or an aftermarket ignition system or an alarm system . But most of us are not looking for anything more than restoring OEM functionality quickly and cheaply. So....

I last purchased these items at a local Pep Boy's store in 2/01. All of them, except where noted below, are packaged and marketed as Exide brand products, which is a very popular brand that I'm sure you can find at many other retailers and mail order vendors. To help you order the correct parts, I have listed the description as it appears on the Exide packaging, as well as the Exide part number, and the price that I paid at Pep Boys. Total it up and you'll get about $20. That's a whole bunch cheaper than a new starter, new battery, etc., etc. Just for comparison, the MazdaTrix price on the OEM cables is about $85. I expect the dealer prices to be about the same, and I seem to recall that even Mazda's Competition Parts department quoted me something in the neighborhood of $62. (Check that if you have that resource available, and please let me know what they told you.)

Description on Exide Packaging

Exide Part Number

Price Each

Terminal Caps

Battery Cable 4 Gauge 50" Top Post

Battery Cable 4 Gauge 24" Top Post

Battery Cable Switch to Start 4 Gauge 24"

Battery Cable Switch to Start 4 Gauge 40"

6 x 1.0 x 20 mm bolt

12-10 gauge 1/4" ring terminal, crimp on (2 per package)

7000150 (or B150CPE?)

2010451

2010424

2230424

2230440


Conduct-Tite #85215

2.49

5.99

3.79

3.29

3.99

check your "box o'nuts 'n' bolts"

I dunno -- cheap, though.


Total Price before local taxes

$ 19.55

As far as installation is concerned, I'll assume that you're not so green that you don't know to disconnect cables from the battery before playing with this stuff, and I'll just describe the fine points as I remember them. If you need more help than this, pick up a Mazda shop manual or pay somebody to do the job. If you're not 100% confident in your ability to do this job right -- DON'T! A minor mishap with this wiring could result in electrical burns to your person, or an exploding battery or even a car fire.

The terminal covers are pretty much a no-brainer, but I'll mention that I cut a slit in the bottom of each terminal cover to make it easier to install and remove them whenever I needed to. Jump starting a friend's GSL-SE (with not-yet-replaced battery cables) is an example of one time you might need to pull the covers out of the way. :)

The 50" cable runs from the battery to the starter, and also has a smaller gauge pigtail that you'll need to take some extra steps to mate it with the fusible link box(es). (The 84/85 12a, manual transmission cars have a single fusible link box, and the GSL-SE models have two fusible link boxes. I don't know how/if this differs earlier models.) For my GSL-SEs, I spliced on two extra lengths of similar gauge wire, mimicking the "m" shape on the original Mazda positive cable, and then crimped the ring terminals onto the ends. (Another tip: make a nice splice by using a high-wattage soldering iron and using shrink wrap tubing. Wire of this gauge will not solder properly with a little 20-watt soldering pen. You can get the requisite tools and materials from Radio Shack, and you should have these tools and skills anyway if you're going to keep a 17+ year old sports car on the road. They probably even have a pamphlet that will teach you good wiring and soldering techniques. Ask at the counter.)

Also regarding that 50" cable, the starter end of the Exide part has a straight end to bolt to the starter terminal. But the OEM part has a 90 degree bend in the end. You'll want to mimic this bend in order to keep this positive terminal-end from contacting the car's negative ground chassis. (That would be bad -- remember what I said about exploding batteries and car fires?) Also, take the rubber insulator off of the OEM part, and slide it over the new cable. You can't be too careful with this stuff.

The 24" top post cable will connect the negative battery post to the body ground at the strut tower. The 40 inch 'switch to starter' cable will connect from there to the back of the engine where the original negative cable went. These two make up the equivalent of the OEM negative cable.

The remaining 24 inch 'switch to starter' cable should be used as a secondary ground to the engine. I'd suggest running it from the strut tower ground to either the alternator bracket or to a point on the side of the engine, near the front end housing. (On the most recent installation, I used a 40 inch version of this cable -- same as above -- to route it down along the strut tower, across the chassis cross member, and up along the side of the engine to the top of the alternator bracket. A friend of mine did something similar with a 30 inch version of this cable.) Everyone that I know who has added a supplementary ground cable has reported consistently higher voltage on their stock voltmeter than they saw before doing this modification. (On my old '84 GSL-SE, I have recorded an increase from about 12.4 volts to 14.2 volts at idle. My current GSL-SE gets a consistent 14.68 volts, and the idle doesn't even change when the air conditioning is switched on!) Along with that higher voltage, I noticed that the engine was more willing to rev and it seemed to run more smoothly at all loads and engine speeds -- all of which is consistent with an ignition system that is getting more juice. Also, my headlights wouldn't dim when I came to a stoplight, and the interior lights were brighter. In any case, for three bucks and change, it's a no-brainer to beef up your electrical system with this additional cable.

In all three of the cable replacements that I've done to date, I found that the strut tower cable mounting screw was a real pain to get back into it's hole. The threads just didn't seem to want to hook up. That was the single worst part of the job, and it added about 20 minutes of frustration to an otherwise straightforward, should-have-been-30-minutes job. Also, with the added thickness of two additional negative cables, versus the single eyelet grounding point of the original negative cable, it would be smart to replace the mounting screw with the longer sized, 20mm bolt listed above. Replacing this bolt with a similar sized stud and nuts would probably be wise, although I haven't done this on any installations to date.

Hopefully, this will help you order and install the correct cables to bring your car's primary electrical system back to peak health.

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