Ohhface

I just purchased a 1986 RX-7 GXL i am new to the Rotary scene. WHen i drive at night i have noticed that the lights will dim then go back to " full power"? anyone have any thoughts or things i may want to check. I can be accelerating or idle. Also how would i go about doing a compression check?
Thanks

Icemark

what is the voltage on your dash voltmeter when this is happening?

The gauge should be showing 14.4 volts or so at all times, if it is dropping under 13.5 you will be having charging issues, and if it is dropping under 12.6, then you will not be generating enough voltage to run the car, and instead are running on the battery.

Ohhface

The voltage meter on the cluster is non operational maybe something i can fix easy? same thing with the oil pressure. Ill have get my meter out to see what it is normally. I think it is above 12.6 cause i have driven it a few times during the night and doesnt die. Only problem i have encountered is after driving the car for a short - medium period of time is when i shut it off sometimes wont start back up for a bit not sure the problem there either LOL

Icemark

Okay then without a working dash, you will need to get a multi-meter and check voltage.

But I would suspect that your alternator is dieing.

Ohhface

I have the meter and when i was going to check i started the car and i was checking the alternator and the + lead on top was getting incredibly hot. What would cause this? I shut the car down when i saw this and didnt get to do a voltage check. Is it an easy fix to get the dash gauges to work?? the spedo tach fuel and temp work. Just the Oil and Volt do not.

Ohhface

Ok so i borrowed a tester the Battery is 13.11v 676 CCA measured 540 CCA rated temp 70F Alternator Load 13.60V W/o Load 13.87V. These parameters seem normal / good to me, from previous cars i have owned... so i am stumped any help would be great.

Icemark

assuming you tested cold? Numbers are rather low for the alt, but if you testing at idle it might be that low.

so again as asked before what is the voltage when the dimming is happening?

Ohhface

Yeah the tests were cold. Ill have to do the test and hope that the dimming happens. It didnt happen well at least i wasnt able to notice due to it being daylight. Ill try testing it tomorrow and hope to catch it and ill do one test on warm v. cold

Ohhface

So i still have not been able to test when it does the dimming i noticed it again tonight as i was driving a few times. I am wondering if the alternator is begining to go out maybe? the voltage regulator... anythoughts?

Scrims

iTrader: (2)

I am having similar problems. Same car - '86 GXL, only my voltage meter works. The dip is completely random, and only for a second. Mine sits at about 13.0v and dips to ~12.2v. Once completely warm, the car sits at about 12v. My guess is dying alternator. Planning on upgrading soon to either FD or ford tempo alt. But that random dip just drives me mad.

Icemark

could also be a slipping belt or if you have used a S5 alt or S6 alt in your S4 and not re-wired correctly, that can cause the problem too.

Ohhface

ill have to look into it the alternator looks to be an OEM maybe wrong part ill check the tension on the belts didnt think of that.
Thanks

Ohhface

So i checked alternator is fine i haven't been able to really catch it on the spikes. at one point i think i may have it went fro 13.9 to 18.95 and charging the battery to 13.25... the belts are fine there is no squealing. The alt has to be OEM spec i bought it from an older gentleman. So i dont think that is the case any thoughts...

Icemark

Woah,,, anything above 15.5 volts can start frying things. If you saw a spike at 18.95 volts the alt's regulator is bad... running that high of voltage will eventually burn up everything electrical in the car.

The alt should be putting out between 14.0 and 14.4 volts. The battery needs at least 13.6 volts (one volt more than the battery) to charge correctly. So if it is running at 13.25 volts, again... it is starting to fail.