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Last Dec I noticed my lights were "surging", as if the voltage to them was not consistent. Haven't checked but my first instinct would be check the regulator. This is a 1990 Crown Vic 5.0L engine.
Also worked in the garage yesterday, with warm weather to test the fuel relay and ECM relay. My last drive before winter, I parked the truck after a lengthy cruise and it would not start. Fuel pump was not picking up. I have also checked the "roll over switch which seems good. I guess I will have to start looking for voltage in the circuit. i know the fuel relay is supposed to operate when the relay coil is grounded by the ECM relay, powered by the ignition switch . I'll start there.
Was the surging related to the engine RPM? As in brighter lights at higher RPM? Or surging in relation to bumps in the road? Left or right turns, or just a very consistent pulsing all the time?
Lights surging, by definition is voltage regulation of course. Make sure regulator and alternator aren't "lifted" or floating relative to battery ground. Can try using heavy jumper cables to ground components directly to negative terminal to isolate and pinpoint the problem. Restored or refurbished trucks often have thick coats of paint interfering with good electron swappage. Rust will do this too. Regulator could be smoked.
I have a #6 wire running from battery negative terminal to chassis, but I will check the connections.
The lighting surge is not dependant on RPM, and appears in the headlights and dash lights at the same moment in time.
I will check wiring at alternator, ground as well.
I will put a meter on the battery when I get it running, to see what is happening with voltage.
The fuel pump relay worked, and then didn't. My first point will be to see if ECM relay picks up with ignition voltage. Will check to make sure ECM pin out is grounded.
With the warm weather we are having I have been working in the garage.
Starting looking for problems with the EEC and Fuel pump relays. With key off the control voltage to both relays was 12 VDC but with key on both circuits dropped to 3-4 VDC. I checked grounding and it was good so removed the connector to the alternator voltage regulator and voltage to relays was the expected 12 VDC. I removed the voltage regulator, brushes are good but I order new regulator and brushes. Hoping this is the cure and I can move onto the fuel tank / pump project.
Last edited by tip49; Feb 16, 2017 at 06:36 PM.
Reason: spelling
I pulled the voltage regulator and installed a new one with new brushes. The EEC and fuel relay picked right up with the proper 12 VDC applied to them. I did take the truck for a little drive as the weather was very mild.
Turned the lights on near dusk, and noticed that the instrument lights on the speedo and headlights are still surging. I guess I will put a multmeter on the headlight circuit to see if the meter can pickup any fluctuations in voltage.
Put a volt meter on the battery; read 13.5 VDCs ignition off and 14.8 VDC ignition on. The meter may not be quick enough to capture the voltage fluctuations, as they only read every 1/2 second.
I may have the alternator tested to see what that would show.
Wondered yesterday about whether the fuel pump is causing the fluctuations. It may be close to being worn out (noise issue) and back feeding into the electrical.
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