Greetings All,

Hope you are well today. I have been noticing a parasitic draw in my 1989 FC Vert. I used a multimeter to read amps, when the ROOM fuse is pulled the reading drops to near zero. With the fuse in, its pulling ~340ma (bad)
This is a project car I have been working on restoring, on-and-off, for years. So the car sits for long periods of time between uses. I trickle charge the battery with a NOCO Genius 2D. When I daily the car it keeps up, though the last alternator detonated the belt around 35mph. Perhaps by the extra load of charging a dying battery that induced more drag on the windings and snapped the belt?

I bought the car with a leaking convertible top, so the interior has had water damage. I leave a car cover on it, or have it in the garage. I have not pulled the carpet yet, but it is on the list. The wonderful original leather seats were torn to shreds so I fit a FB driver's seat (no electronics). All headrest speakers are unplugged.


I have replaced the following;

1. Alternator - New Duralast unit (belt snapped on the other one. No one [Autozone and Napa] tests these anymore bought new to troubleshoot).
2. Tried a junk yard alternator as well.
3. Added 8ga wire run to existing harness from battery to positive on alternator.
4. Added grounds to intake manifold, one large ground strap, and several thinner wires to fuel rail area. Also sanded the grounds points to fresh clean metal.
5. Tested door and trunk switches for the interior lights (placed a smart phone inside trunk, videoing it turn on and off).
6. Had the radio (with patched wire harness from previous owner) unplugged, and the cigar lighter unplugged.
7. Had the center dash warning light bar unplugged. (The light module was destroyed by (most likely) a spilled soda).
8. Had all the center console switches unplugged (mirrors, fog light. vert headrest speaker module, security light). These are all simple rocker switches (that I cleaned) no other electronics.
9. Replaced the battery 3 times before I realized what was going on. I thought the NOCO battery charger was destroying them from being plugged in for months at a time.

• I do not know how to test the diode on these alternators without disassembly, if anyone has suggestions, I am all ears. The harness on it have 2 pins, and the main positive power lug.
• I know my 1990's verts had security system that would arm when locking the driver door outside with the key. When armed, the light on the dash would light.
• I have never known the security system on this car to work.
• As mentioned the previous owner didn't understand the complex nature of the stock radio, with its 2 Pioneer amplifiers for the headrest speakers, and dash speakers. They

cut several wires to hack into it instead of using a adapter. I patched it back together with an old, stock wire harness from junkyard and eventually soldered everything into place. That said, I still have the factory amps plugged into there harnesses.

• The wiper switch has the common problem of only working on one setting. I am not sure what fuse that is on, or if a broken relay would cause a draw?
• The convertible retractor system (switch on cluster) works flawlessly.
• The cruise control module works, though the switch has broken the plastic bosses that hold it in.
• All lights inside and out are incandescent, no LED.
• I have not inspected ALL the wire harnesses throughout the car, but the visible ones seem fine. No chafing in the insulation.

Is there anything else I am missing? Perhaps unplug the security module? I don't know where it lives.

Help me Obi Wan Kenobies! You're my only hope!

PS. If anyone knows a good shop that will refurbish my two alternators, please let me know. I am willing to ship to the continental US.

 

I think I can probably help you best as anyone as far as the series 5 pioneer stuff goes. Show us some pictures of the carnage and we can start from there.

Alternators aren't too terrible to work on either. There's a section in the FSM that shows you how to disassemble. I replaced the bearings in mine many years ago.

As far as troubleshooting goes, it is possible that a wire has worn bare and is grounding out. What I would do first is to check the list of items on that circuit, listed in FSM Body Electrical p. T-14. Unplug it all and start plugging stuff in until you have found the short. Looking on the list, the theft deterrent system, aka the body cpu (long black plastic box in drivers footwell), is a high priority. I haven't seen a single one of those that hasn't failed, even in a car that has been well cared for. I've got a few posts on how to repair them yourself, or I have done a good few of them. Any competent electronics repair should be able to easily fix it as well.

I have also went through all of the amplifiers for my car and have a thorough thread on the Pioneer systems. The only amplifier I haven't been able to find a manual for is the headrest amplifier. It was manufactured by Panasonic and not Pioneer. Head unit, front and butt speakers amplifiers are all Pioneer with NEC and Sony for the brains. https://www.rx7club.com/2nd-generati...ssues-1148850/

 

Hi Pyrrom!

Hope you are well today. WOW MUCH GRATITUDE for the extremely helpful post!!

Of course it is raining here all weekend, so I will have to pluck at it when it dies down. Thanks for the tip about isolating the circuits one by one. I can't recall any wear points in the routing of the body harness, so I am presuming that would be fine. If troubleshooting light bulbs / sockets / wiring will pulling the bulb do anything? If the wire is worn through, and grounded, unplugging the bulb wouldn't matter, right? Or conversely; if the worn wire was 12V grounding out, unplugging the bulb at the end, wouldn't matter? Other issues would present them selves, right? Like a blown fuse, or fire,
This has always been a fuzzy spot in my head.

When I was troubleshooting the custom harness adapter I made, I noticed that the head rest speakers, and all other speakers / amps would turn on with *one* wire added to the 12V ignition switch. (Red and Yellow on the Metra harness, maybe?) I am not sure the exact wires or colors, but I do believe I have bridged 2 separate circuits (RADIO and CIGAR, maybe its been a while) with this adapter. Funny thing is, that made everything work, INCLUDING THE WINDSHIELD WIPERS!!!! I know wiper switches break and before I fixed the OEM radio harness, the wipers did not work on ANY speed. With this unintentional "mod" I have at least one speed, with the redundancy Mazda built into the module.
How difficult is it to refurbish the wiper module? I remember ICEMARK (RIP, BROTHER) helped me out when my first seven's failed.

That said, when troubleshooting the draw, I UNPLUGGED this custom harness. SO <SHRUG/> ???


As for the 7's CPU module, Just had a quick image search, and found these:
I know on my second 7, the blinker module died, and I had to replace that. So I know exactly what long black box you are talking about.


I will pull this bad boy apart and see what how much corrosion is on this. Are there aftermarket versions of this? The Porsche 944 I have worked on had a similar looking setup crammed into a relay size module that lives on the main fuse panel. The aftermarket version is a solid state upgrade that replaces the aging, old, and failure-prone electronics. The 944 owner has had zero issues with it. Perhaps something like this exists for the Seven?

Looking at FSM page T32 I can see the general internals of this and there are a lot of points of failure. I am also guessing they didn't use a conformal coating on the PCB.

One other thing of note: Years ago when troubleshooting a blown fuse with the fog lights, I noticed the plastic, FOG fuse holder was melted. The contacts are fine looking, just the plastic area around it. The fog lights did work so I moved on. Perhaps a puddle of standing water was down there, it happens..

Here is the Security system. As noted with rust, on eBay. Where is this located? Is it also a known failure?

86-91 Mazda RX7 FC OEM Anti Theft Control Module FB67-67-790



Thanks again for all your help. I have been putting this off for a hot minute, and despite the current rain, and the shredded top (can't tell when its down!), this thing is a fun weekend romp!
More to come!

Cheers!