volt drop testing an ignition switch
Posted to Technical Tips Forum on 3/17/2009
23 Replies
This is one I fixed a month ago. The complaint was
intermittent no start and several idiot lights
intermittently lighting up.
After consulting my wiring diagrams,I decided to attack the
circuit at the most accessible spot. I went for the
underhood fusebox. [multimeter dual trace hookup]
I decided to setup a dual trace to show you exactly what a
voltage drop is(not everyone knows).
This is a pic of what it looks like when the problem
occurred. [voltage drop testing, dual trace] The
voltage going into one circuit of the switch was 12.32v.
Only 1.82v was going out under load. The difference in
voltage between the two measurements is the "voltage drop",
in this case, a 10.5v "voltage drop".
On this model, the instrument bezel is easily removed and
gives access to the rear of the switch. [2000 Chevrolet
Malibu, Ignition photo] While observing the dual trace
setup, I gently pushed rear of the switch towards the front
and the voltage drop disappeared. [no more voltage
drop]
This is an internal view of the switch I autopsied. [2000
Chevrolet Malibu, Ignition photo] It uses a complex
assortment of tumbler pins that apply pressure to superposed
stainless "finger blade" type contacts. The whole thing
appears quite cheap and flimsy, and I am not surprised they
have a high failure rate.
Hopefully this will help some demystify what voltage drops
are.
Karl from Quebec
23 Replies Received
(View Replies)
23 Replies Received
(Hide Replies)
|