SA Electrical Help

[infernosg]

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?

[t_g_farrell]

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.

[infernosg]

Originally Posted by t_g_farrell

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.

I'll take some pictures later today. I verified the tach signal is from the lead igniter (Y/G wire) and it is plugged in. The fact that I'm seeing less than 12V with the car running at the battery and alternator makes me think something's up. Perhaps something in regulator got shaken loose since it was delivered by truck. There are a couple disconnected connectors over by the clutch master and I was able to identify and reconnect one: the brake fluid level sensor. I'm not familiar with the solenoid you mentioned. If it controls the idiot lights it could be the culprit since all the lights in question usually get switched off after the car is started. Right now the only ones that go off are the "brake" and "seatbelt" lights.

[chibikougan]

Shameless thread bomb of the Manuals....

http://foxed.ca/index.php?page=rx7manual#firstgen


*smoke bomb*

[infernosg]

Originally Posted by chibikougan

Shameless thread bomb of the Manuals....

http://foxed.ca/index.php?page=rx7manual#firstgen


*smoke bomb*

Been digging through those quite a bit lately. Unfortunately it doesn't have a 1979 FSM and there are significant differences between 1979 and 1980 when it comes to the charging and ignition systems. Hell, my wiring harness differs from the 1979 one on that site. Maybe it's because I have an early build (March 1978)?

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.

[infernosg]

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.

[Pete_89T2]

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?

[infernosg]

Originally Posted by Pete_89T2

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?

I agree, but it definitely controls the A/C. With it disconnected the A/C doesn't work at all. The other "A/C relay" does something with idle control. With it disconnected the idle doesn't bump up to compensate for the extra load on the engine. I almost wonder if this was some kind of aftermarket A/C system installed after the car arrived stateside.

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.

[chibikougan]

Looks like it may have had some fusible links so they put in a relay.

[chibikougan]

There is a blue and yellow that go into the cab for the:

Ignition

Alt Warning Light

a-10 connector...

[t_g_farrell]

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.

[infernosg]

Originally Posted by FC Zach

Most parts stores have the ability to bench test alternators, whether or not this test can be done with your application, I don't know but it's worth a shot.

My guess is the regulator but I'm not familiar with the first gens and their parts.

I'm leaning toward the regulator as well. I just wish I knew how to test it. I mean, they really aren't expensive to replace. RockAuto has an option for less than $10 although the OEM piece is $100. Even replacement alternators are in the $20-30 range after returning the core. I still can't explain how something that was working a week ago suddenly breaks during transport.

Originally Posted by t_g_farrell

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.

Thanks. I found a thread on the other forum where someone was describing my condition of the voltmeter never switching over to the alternator. In that thread this, along with the other warning lights, was attributed to a bad voltage regulator.

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.

[tim.]

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?

[infernosg]

Originally Posted by tim.

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?

I unplugged and reconnected everything from the battery to the alternator to the voltage regulator and that didn't seem to fix the issue. I decided to pull the alternator to get it checked out and I've got the battery on a trickle charger. I'm going to tear into the instrument cluster later today and triple check the coil and distributor connections.

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.

[FC Zach]

Originally Posted by infernosg

Update: I took the alternator to Advance Auto Parts (don't judge) and their machine failed it.

Is there some type of stigma toward Advance that I don't know about? I can see this being said for Auto Zone because of their separate search and check-out lines as well as poor service in my area but why Advance, does your store have bad customer service?

I must say I'm a little biased since I worked for the company for five years, best store in the district too