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I think I'm having some trouble with the voltage regulator on my '79 RX-7 and I'm looking for some help with servicing it. First, I have to make a request...please don't tell me to just change to an alternator from a later year with the regulator built in. I know that's an option and may be the right thing to do, but I am the original owner and want to keep it as original as possible.
Here are the symptoms. I went to drive it one day and it seemed that the battery was completely dead, which was odd since I just put a new battery in it a couple of months ago. I put a charger on it and as soon as I plugged it in I heard a clicking sound. As I was unplugging the charger I noticed that it wasn't drawing much current...less than 1/2 amp, which would be odd for a dead battery. When I plugged in the charger again I heard the click again and then some buzzing. I decided to give up until I could get my brother to help me do some troubleshooting. We immediately recognized that the click was coming from the regulator, so we removed it and took the cover off. It looks good inside and the resistors on the bottom look ok...one measures 10ohms and the other about 36ohms. Both relay coils have resistance.
I haven't done thorough checking but some quick checking of the gaps looks like some are not correct. So will incorrect gaps cause this problem? If not, what could? What is the proper way to adjust the gaps. The manual says to "adjust them by bending stationary contact bracket. To me that implies there is one bracket to be bent to adjust all three gaps...is that right? What's the best way to bend the bracket?
Thanks guys!
Rich
P.S. I tried to attach the schematic page that shows the charging circuit as well as the service manual page that discussing testing and adjusting the regulator, but attachments start uploading and get to 90% then stop. I waited about 10 minutes before canceling.
Try seeing if the alternator is charging the battery by measuring the voltage across the battery terminals, not the connectors, while running. If it's a bad regulator you might see no charging to wilding varying voltage. The gaps are for the internal relays. They are electro-magnetic so I'm not sure the gap size is super critical. You might be able to compensate for worn brushes, but I doubt that is the issue. They probably would have made the regulator brushes replicable like what's in then alternator. And that could be the issue. The brushes inside the alternator. You can get new brushes for it for about $2.11 from RockAuto if you want to take your alt apart.
A new voltage regulator is about $100. A new 50amp alternator is a bit more.
Thanks for the info KansasCityREPU! I've changed my thinking on this. I really don't think there is anything wrong with the voltage regulator. This all started after I got into the car to take it for a drive and couldn't because the battery was completely dead...or so I thought. No dash lights came on, no starter, no nothing. So I put a charger on it and the regulator clicked, so I suspected a problem with it. But the battery was drawing almost no current from the charger, so it's not dead.
So now I'm thinking I have a fusible link problem. It'll be a day or two before I can get out there to check it out. I'll update when I can
Well, this makes me feel a bit foolish, but I don't think I've seen this before. The battery was indeed completely dead...less than 0.5v. Initially, it was drawing less than 1/2 amp from the charger, but after a while it came up some, so then I decided to use my maintainer to slowly top it up. It has a sequence of about 8 LEDs to indicate how much charge is in the battery. After leaving it overnight only 3 lights were lit and the charger was quite hot. So I put the regular charger on it and it was drawing about 3.5A. I left it all day and it gradually came down through the day until it was a little under 1A, so I put the maintaining charger back on and left it overnight. This morning all but one LED was lit, so I'll leave it until they are all lit.
So now I have 2 concerns.
1) How did this happen? I don't think I've ever seen a good battery (this was bought on April 29 of this year) go so completely dead. I can't say with 100% certainty, but I am almost certain that I didn't leave a door open or any lights on.
2) Is this battery damaged?
It's possible a bad alternator or bad regulator caused the drain. Once you get it started again this can be tested. Make sure the alternator is charging, and not over charging. With a bad regulator I would guess the amps/voltage would be zero or all over the place. You can also change for voltage drain with the battery connected. South Main Auto on YouTube has a good video on checking parasitic drain.
Sorry, I just thought of this after posting. I really don't drive this car as much as I should. I bought the battery it late April, installed it in early May, and drove it maybe twice after that...then it was completely dead. So, unless the alternator or regulator can drain it just sitting, I don't think they are the problem. I really think it's either a light left on (I don't think so, but can't guarantee it), or a bad battery. Correct me if I'm wrong. I just went out and checked and after sitting all day on the maintaining charger the last LED is still not on.
What brand battery did you purchase? Putting the issue of a bad alternator/regulator issue aside, if I read your post correctly you have tried both "slow" and "fast" charging options and the battery will hold a charge is that correct? If your attempts at charging your battery were performed either out of the car or with with both the POS and NEG cables disconnected it would eliminate the car as being a source of the issue. I would return the battery for an new one, or a different brand, because a battery less than six month old that can't be charged is dead and needs to be replaced. The only other thing I can think of is if it's a lead acid battery and the cells are not completely covered with water there could be an issue created during fast charging, and all it can take is one bad cell however, a battery this new should not be giving you these kinds of issues. Hopefully you bought it from a reputable business and don't have any issues returning it.
Thanks Seniorchief! This is a good AGM battery from Napa...$250 worth! I don't have both terminals disconnected from the battery, just the negative. That is sufficient to eliminate anything in the vehicle from causing the problem. On the maintaining (slow) charger, the top LED was still not lit after sitting overnight again, but the others were. I removed it and let the battery sit for a couple of hours then took a voltage reading. It was 12.98v. About 3.5 hours later I took another reading and it was 12.95v, so it looks like it's holding. I'll check again in the morning.
Glad to hear it's holding a charge 64mgb, I'm a fan of AGM batteries, and have used them in the past. I had an Interstate AGM battery in my RX7 a few years back that lasted nine years.
I took another reading this morning and it was 12.91v. I'll let it sit today and if it looks ok tonight I think I'll connect the negative terminal and see what it looks like in the morning.
The plot thickens yet again. When I got home from the golf course yesterday I took another reading and it was basically the same that it was in the morning...12.92v. So I decided it was time to connect the negative terminal to the battery and see what happens. When I did I ran it through my ammeter to measure the current draw. When I connected it I heard a relay in the regulator engage and the current draw was nearly 3/4 amp. So now I need to try to figure out what is causing that. I think I'll start by removing the fusible links one by one and see what that tells me. Then if need be I'll start removing fuses from the fuse panel to try to isolate the offending circuit.
It looks like I have n alternator problem. When I remove the positive lead from the alternator the current draw goes away. I used the diode/continuity setting on my DMM to measure the voltage drop across the diodes and it's 9mV, so one or more diodes is/are shorted. I ordered replacements from RockAuto this morning...I wish I had thought to order brushes as well, as long as I'm going to have it apart. Oh well, we'll see what they look like and go from the there.
Forgot to follow up on this. I did replace the rectifier and brushes in the alternator and reinstalled it on the car. I started it up and everything looked great so I took it for a short test drive. When I got back into the garage I found that the radiator is leaking So now that's the next problem to tackle.
There are worse thing that could require your attention besides your classic Rx-7. Enjoy the ride, after you've fixed it.
You are correct sir! But it has been frustrating to not be able to drive it much for the past couple of years. It's been one problem after another and I'm just not as good about getting out there and getting it fixed as I once was. Hoping to get the radiator pulled out this weekend.
To me, the worst part of removing the radiator are the four long winded bolts that hold the clutch fan to the engine. Hopefully they glide out and don't fight you to the last thread!
With any luck, it's a small, repairable leak. Not sure how long it's been since you've needed any radiator work, but it's a new, expensive world now, that drives most uses to the aluminum, aftermarket route.
The radiator is out! I'll take it to a repair shop tomorrow to see if they can help me out. But now my question is, what will be the best way for me to flush the system? The radiator is out and the upper and lower hoses have been removed. I have not removed the water pump yet, but I will replace it while I have the system open.
You can remove the plug from the bottom of the block to completely drain the keg.
Maybe flush it out from either end of the hard line to the heater core. Either the radiator end or the fire wall. Might be a good time to replace both the firewall lines too. The long one is a little pricy.
Thanks Banzai! I'll pull that plug and drain it, then reinstall it and do the flushing. I am hesitant to replace the heater hoses since they are original...46 years old and going strong! But I think it would be prudent to do that now. I did pick up the longer hose several years ago. It's sealed in plastic so I think it will still be ok. I was thinking I had bought both but don't see the shorter one laying around anywhere.
What do you think of this idea for flushing?
Remove the thermostat then replace the thermostat housing with big hose attached. I 3D printed a couple of adapters that I can connect a garden hose to and clamp into the big hoses...one with male threads, one with female threads. I figured I'd connect a garden hose from the outdoor spigot on the house to the lower radiator hose, and a short piece of garden hose to the top radiator hose to use as a drain. Then turn on the spigot and backflush the system. When complete I'll remove the block plug again and maybe blow some air through the system to try to remove all old fluid.
And the saga continues! My brother helped me flush the system last weekend and that went well. Here are all of the plugs and adapters I 3D printed...we used all but one of them and they worked well.
All of the parts I ordered have come in but the two short heater hoses are the wrong ones. I found a source for the short curly one at the firewall and that should be here in a couple of days. The other one that feeds into the lower radiator fitting is pretty simple and I think I can just use a regular piece of hose for that.
It dawned on me that while I'm doing this work I should rebuild the OMP. As it happens, I ordered 2 spare rebuild kits when I restored an '85 GS about 15 years ago. So I set about taking the OMP off the engine and was quite shocked to find that the linkage from the carburetor wasn't even connected at the OMP! It hasn't been pumping oil into the carb for many years. I'm quite thankful that I've been dumping 8oz of Marvel Mystery Oil into the gas tank every time I fill up for many, many years. It appears that has saved this engine.
Now I need to decide if I should replace the plastic oil lines to that run from the OMP to the carb. They feel ok to me, so I'm tempted to leave them. Thoughts?
The factory OMP lines will be hard to find. Years back the long one was NLA. Not sure about the short one. Be very careful if you make your own. The line has to be able to take the heat.
If they aren't leaking, I'd probably re use them. I do remember a thread on here awhile back where someone built replacements using something else. Don't remember the specifics. Would need to do a search in the threads.
You should definitely reuse the OMP feeder lines if they are not leaking. People have tried to replace with alternate sourced tubing but it turns out that the capillary action of the tubing is very helpful for keeping them full even when the pump isn't active and the car is sitting. At least that was the theory.
07-30-24 | 08:03 PM
So now that's the next problem to tackle.
