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!

 

Ok, a few things. That black CPU box is exactly what I was talking about. All of the ones I have repaired have had the same power capacitor failure with varying degrees of damage. Conformal coating on the board doesn't protect anything if the failure occurs under the coating. There aren't any replacements that I know of, and if you were to find one, it would be the same age as all the other ones that failed. I'm working on a solution for this, hopefully I'll have something this fall. In the meantime, a repair of your existing one is still feasible and I have done a bunch of them.

Might also open up your fuse block at this point. I wouldn't rule anything out without inspection. Since you mentioned bridging circuits, that would be a point I would inspect.

Did your car still have the factory stereo plug, and you added the Metra adapter, or did you use the Metra harness to fix a messed up factory harness?

There isn't much going on inside the wiper module. I opened mine up to see if there were any capacitors. It just needed a good cleaning. I can't find what I did with those pictures though.

 

Hi Pyrom,

I finally got some time to pull out that CPU and disassemble it. There was corrosion on the bottom screw. The wiper module seems fine. Just a medium strong odor of flux. There are three capacitors on the bottom that seem to have corrosion under the striped side (Cathode).

Can I just sand off the conformal coating and resolver the joints? The caps don't seem to have leaked, or domed their tops.

 

All of these electrolytic caps should be replaced. There is likely corrosion you can't see, especially around the C1 capacitor. There is discoloration of the traces on the back of the board indicating that there is an issue there. I wouldn't sand anything. That coating is fairly rubbery. You can scrape around the joint you need to get to with a hobby knife. I would not only remove the capacitors, but completely clean the pads that the caps were soldered to. Remove all old solder from those pads, clean with alcohol, and add new solder with the new capacitors. Be gentle removing the old caps. When those traces start to discolor like that, they're already starting to get fragile.

 

The original audio harness was cut clean off. Only the secondary speaker harness was there. Years ago I cut a harness from a donor car in the junkyard. I don't' remember what year it was or vert / hard top.

I spliced that harness into the what was left of this car's harness wires. I believe I got them all correct but there were several that required extensions. All I had was blue remote to do the extension.

THEN I convert to a Metra harness out to my aftermarket head unit.

At first I had the dash and door speakers wired through the OEM amps, but that didn't sound great. So I wired them directly.

Next I did a three way leg for all the speakers, so that I can bypass the OEM amps, or have it go to the speakers directly.

That said, I am aware this harness is a mess, but it all works.

As for the bridging of circuits, I must have tried it, but didn't keep that configuration. I did solder in spare leads for the power, remote, battery and ground wires for future use. Those are taped off so not shorting is possible.



This is the current state of the harness. It coils up under the radio, taking up the blank spot

I tried to separate out the wires to see if I mixed any up

I tried to separate out the wires to see if I mixed any up

OEM Harness repaired with Junkyard harness

Metra harness to Kenwood harness plus pigtails out for speakers and spares

 

Thanks for that input. My Digikey-fu is meh at best. Do I just get the same values for the new caps and try to find the correct dimensions?
You mentioned repairing these in the past. Do you just replace the caps?

It looks like the caps say 16V 10uf . Does that sound right? Is there a decimal I am missing?
Cheers!

 

As far as the repair I do on them, its usually replacing caps and cleaning up corrosion. Sometimes I have to reroute stuff if the traces are too far gone, usually because of C1. I may have plenty of extra caps from the last one I worked on. PM if you are interested in sending it to me. If you want to do it yourself, make sure the capacitance is the same, and the voltage rating is equal to or slightly higher than the existing caps.

For the stereo part, hoo boy. The two connectors you have are for the S5 stereo. If you have those spliced back in correctly, good deal. The front speakers and subs get audio signal directly from the head unit and are driven off of them. They both share a source. The only difference with the subs is that there is an in-line amplifier for them. The connectors on the harness on either side of that amplifier can be plugged into each other to bypass that amplifier. As far as getting these to sound good, I completely understand. The reason I am trying to resurrect the stock head units is because I can hook those up and they sound great, but an aftermarket one I just can't get set right. I think that part of it is that the amplifier in these Pioneer units is set up for the amp to use front speaker audio, while an aftermarket unit is the opposite. Just my theory so far, its subject to change. Something I would do, just my opinion, I would undo a lot of that bypass wiring and focus on getting the stock wiring correct for running speakers and then we can troubleshoot better.

I just noticed something. You have your amp control line and power antenna line (blue and blue/white) spliced together. These must be separate. Here's why. In the stock head units, the power amp line is supplied +12v from the head unit and the amps are grounded to the chassis. No negative return for those. The power antenna works on the opposite polarity. It has +12v coming in to the head unit, and when the head unit wants to raise the antenna, it grounds that +12v at the head unit. Both of those lines are fighting each other right now. Positive is flowing from your antenna to your amplifier and out to ground. Might be part of your big drain.

 

So you have battery drain? I have a vert as well and I noticed my battery was dying quicker than usual. I found out the trunk convenience light stayed on even with the car locked and alarm set.