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RX-7 1st Gen Specific (1979-85) RX-7 1979-85 Discussion including performance modifications and technical support sections |
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07-26-2016, 10:30 AM | #1 |
IT'S ALIVE!
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SA Electrical Help
I just picked up a clean SA ('79) sight-unseen. I had a dealership local to the seller check it out and they found no issues. However, it has some electrical issues I wasn't expecting as neither the dealership nor the previous owner mentioned them:
1. The tachometer doesn't work. I verified with a timing light all four plugs are getting spark and the resistance across the posts on both igniters is within spec. The gauge isn't getting the engine speed signal and is always displaying the voltage. 2. The "add oil" light is on but the oil level is at the "full" mark on the dipstick. I haven't checked the oil level sensor yet. 3. The "add coolant" light is on but both the radiator and overflow bottle are full. I haven't checked the coolant level sensor yet, but grounding the connector to the negative terminal of the battery doesn't make the light turn off. 4. The "gen" light is on. Voltage at the battery and alternator "B" terminal checks out around 12.25V with the car off. With the ignition on and the car running the voltage is 11.75V at the battery and 11.50V at the alternator. According to the dash voltmeter increasing engine speed increases voltage, although it does show voltage going well past 14V so I don't know how accurate that is. I can't find a 1979 service manual to check the alternator as it appears to be different from the 1980. I don't think the dealership and seller are lying when they said nothing was wrong when they last had the car. I'm thinking there's something wrong with the charging system that's linked to everything as it seems unlikely all these sensors would fail at once. I can't think of anything that could have failed during the delivery of the car. Am I missing something? |
07-26-2016, 11:42 AM | #2 |
Waffles - hmmm good
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1. The tach gets it signal from the leading ignitor. If the lead isn't hooked up that would explain it. Pull the elect. diagrams to verify the lead thats required.
1 & 2 & 3 & 4 May be related to the solenoid over by the clutch master. It controls the idiot lights and may be not turning them off? Something to check. 4. You should be seeing over 12 volts when idling and up to 14 volts at higher rpms. The 79 has an external regulator so you may need to look into it to make sure its working correctly. Its also over on the fender by the clutch master. All this aside, it was delivered via a truck? Maybe some connections vibrated loose. I'd look around in the bay for any dangling connections. You could post up some pics and maybe get some help by crowd sourcing on here.
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1980 GS stockport, Fat Nikki, RB Dual Facetfuel pumps, Holley regulator, RB Street port exhaust, 2GDFIS, MR2 MK I electric fans, 2G strut bar, relayed fans, lights and fuel pump, LEDs Project Fat Nikki Budget 12A rebuild Video setup < $30.00 |
07-26-2016, 12:34 PM | #3 | |
IT'S ALIVE!
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07-26-2016, 12:47 PM | #4 | |
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Shameless thread bomb of the Manuals....
http://foxed.ca/index.php?page=rx7manual#firstgen *smoke bomb*
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07-26-2016, 01:48 PM | #5 | |
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I took some pictures of the area by the clutch master cylinder. I have four connectors that aren't connected: From the insulating muck on them it appears they have never been connected. Only two would make a matching pair anyway. Other than that I verified the alternator regular was fully connected and nothing looked out of place or broken. Since I'm reading less than 12V at the battery and alternator I'm thinking the regulator and/or alternator are somehow bad. If anyone knows how to check their function on a '79 let me know. |
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07-26-2016, 04:51 PM | #6 |
IT'S ALIVE!
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So I've identified the four unplugged connectors. Apparently all these cars had the same harness whether they were MT or AT and Federal or CA emissions. All the unplugged connectors have something to do AT and CA emissions so they are rightfully disconnected in this car.
I can't seem to find anything loose, broken, or disconnected that's vital. I'm confused by one particular relay, however, that doesn't show up in any of the parts lists. Does anyone recognize this: The blue and yellow wires travel up along the firewall and into the cabin on the passenger's side: Because of this I assumed it has something to do with the optional A/C on the car. However, the A/C relay is already accounted for, although the relay has "Window Relay" stamped into its side. Looks like an alternator and/or external regulator problem is still the top hypothesis. |
07-26-2016, 05:40 PM | #7 |
Lifetime Rotorhead
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Hmm, that relay wiring does not look at all OEM - if it came with the car, I would expect some sort of plastic connector for all pins, not spade lugs on each terminal & individual wire.
I'd say it's part of some aftermarket accessory that a PO put in or had put in - maybe part of an alarm system, or car audio accessory? |
07-26-2016, 09:30 PM | #8 | |
IT'S ALIVE!
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Still no "aha" moment though. I had my wife help me for a few moments and I was able to confirm voltage does increase with engine speed but not nearly as high as indicated on the gauge. I also figured out why the steering wheel was so sloppy. Some kind of plastic o-ring at the end of the steering column has completely rotted out. Not sure if I'm SOL or if there's some way to replace it. |
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07-26-2016, 09:32 PM | #9 | |
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Looks like it may have had some fusible links so they put in a relay.
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07-26-2016, 09:48 PM | #10 | |
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There is a blue and yellow that go into the cab for the:
Ignition Alt Warning Light a-10 connector...
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07-27-2016, 06:43 AM | #11 |
Waffles - hmmm good
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The SAs have the tach signal on the leading because the stock ignition disables trailing on
certain conditions. Your car looks fairly stock so I would say it probably works this way. I bet your alternator is just weak. I've seen the dash lights stay on like that if the voltage is not good sometimes. Have you checked the battery cables yet? They may be original and falling apart internally. You're having fun now! I'm jelly. I'll take a look at my haynes manual to see if it has any extra words on dealing with the regulator.
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1980 GS stockport, Fat Nikki, RB Dual Facetfuel pumps, Holley regulator, RB Street port exhaust, 2GDFIS, MR2 MK I electric fans, 2G strut bar, relayed fans, lights and fuel pump, LEDs Project Fat Nikki Budget 12A rebuild Video setup < $30.00 Last edited by t_g_farrell; 07-27-2016 at 07:32 AM.. |
07-27-2016, 07:59 AM | #12 | ||
IT'S ALIVE!
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My battery is only outputting around 12V as it stands so I may just throw it on a charger to see if that helps any. When the car is off I'm getting the same voltage at the alternator terminal as I am across the battery posts so I don't think it's the wiring. |
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07-27-2016, 08:06 AM | #13 |
Plate Spinner
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The symptoms you are getting are the same as when I broke a belt on my 79, so I would check the harness connectors from the alternator to the voltage regulator, and the regulator to the instrument cluster. they might be corroded enough to drop the voltage below where the regulator can see it. It might have gotten jostled around during shipping?
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07-27-2016, 09:12 AM | #14 | |
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The car won't be going anywhere for a while as I've got the steering column pulled apart to replace the upper bushing, which had crumbled to pieces causing play. Update: I took the alternator to Advance Auto Parts (don't judge) and their machine failed it. It looks like one or more diodes in the rectifier are bad so I'll be ordering a replacement from RockAuto. I still don't know if the regulator is also bad but this is a start. Last edited by infernosg; 07-27-2016 at 11:52 AM.. |
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07-27-2016, 10:44 PM | #15 | |
RCC Loves Me Not You
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I must say I'm a little biased since I worked for the company for five years, best store in the district too
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1993 Yamaha GTS1000 1992 Celica Turbo AllTrac 1987 RX7 Sport 1979 Yamaha G1, KM24 powered 1975 Dolmar KMS4 |
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