I've developed a strange problem on my 74 mav. It was perfectly normal then I tried to start it and I get nothing. My gauges light up for a second and shut off. The dome light dims the the second I touch the key. Battery has good voltage. I tried to bypass the solenoid and nothing. It will click once and make the smallest spark. I ordered a new solenoid and voltage regulator. Hoping that will fix it. I tore apart the old solenoid and the side lugs have scorch marks but not too terrible. Everything else inside seemed fine. I also cleaned every ground and connector to the voltage regulator. Any ideas?
Zero chance a voltage regulator will fix it. You're losing ability to carry heavy current. Suspect components are battery, cables, their connections and the solenoid.
My bet is the solenoid just died then. Everything else seems to be in order. I tried to start the car from the solenoid and nothing happens. Barely even a singular click or sparks.
I suspect your battery. It takes more than "volts" to start a car. It may read "good voltage" and still be defective. Take your battery to a battery store and have them load test it.
The IVR produces a pulsing voltage that averages out to 5v. When working properly, produces on off voltage approx once a second.
No just pulsating DC, zero to 12v and back to zero. All the circuit is doing is heating a bimetal strip inside gauge. Constant voltage would overheat gauge. 12 vac is zero to 12v positive, back to zero, then swings to 12v negative and repeat. With house current, happen 60 times a second. Can be any frequency actually, most of Europe uses 50 cycle current.
I'm not so sure about that. Isn't a half-wave rectifier just zero to V+ and back to zero? An ignition coil would never achieve inductance & fire a spark plug with 12V DC. It has to be "changing DC" (back & forth from 0v to 12v) which is "seen" as alternating current...
Nope, an example of alternating current is +12v, 0, -12v, 0, +12v, 0, -12v, etc etc. Before the diodes in your alternator rectify the voltage, that's exactly what's happening.
Problem was the battery positive cable decided to short itself out internally. tore it apart and the inside was cooked. Replaced it and everything returned to normal. I was testing the starter solenoid and was getting like 1v at the solenoid but 12v at the battery so that's how I figured it out.
Glad you found it but short out isn't what happened. More likely acid creeped into terminal and corroded to point it could no longer carry the current demand. At that point it remaining strands burned in two.
I had the same problem wit a Ranger pickup. The positive cable going to the starter had burned almost into and it was not getting enough power to start. I took a remote starter cable and ran it from the battery to the starter and it started every time. replaced the cable. Everyone with a no start should remember it.
