You won't see a change on a digital meter unless it just happens to sample on the "low."
An analog meter will dip just a touch, depending on quality.
If you have an older Simpson 260 meter, with a taut band meter movement, you can see it well. (If you do, and want to sell it, let me know.
I'd use an led; yellow or green is easiest to see. A green led, a diode, and 1000 ohm resistor make a great trouble light. It can easily be built into the broken test lead you have for a meter laying around, if you're an electronics guy.
A Red/Green led that only has two leads is a great one to use; the leds are reversed, so red or green tells you what polarity.
You can likely buy one of these ready made, if you look.
Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.
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