dwell meter

[71 pagoda]

What is the correct way of hooking up a dwell meter to a 71. I was told that you have to attach the leads to the  stock transisterized ignition box under the battery or you wont get a correct dwell reading.
Thanks
Larry
71 280sl  w/transis. ignition

[113gray]

Hi Group, While we're at it, how about including where the meter is correctly hooked up for an earlier NON-transistorised car? TIA.   -JP-

[hands_aus]

Larry, 113gray,

On a NON transistorized ignition,
Black wire of the dwell meter to the negative terminal of the Battery.
The other wire connects to the coil terminal with the wire that goes to the Distributor

I don't know about the Transistorized Ignition connections.

Bob (Brisbane,Australia)
early 250 SL, RHD

[George Davis]

The BBB gives directions for connecting dwell meters on transistorized ignition cars, but the connections depend on the meter used.  Some, but not all, of the connections are listed below. (BTW, these directions do not apply to types 108.067, 108.068 and 109.057).

For SUN engine testers WITHOUT change-over switch for transistorized Coil Ignition Systems -
RPM/dwell angle testers TDT 5,6, 12, 216:
Red clip to outlet of 0.4 ohm series resistor (two outgoing cables at outlet).
Black clip to inlet of 0.6 ohm series resistor (resistor between switching unit and ignition coil).
Note that other testers are also listed which seem to have more connections, so I'm guessing they are the bigger testers that shops of that era would have had.

For SUN engine testers WITH change-over switch for transistorized Coil Ignition Systems -
Red clip to ignition coil terminal 15
Black clip to ground

Bosch mini-tester EFA 226:
Red clip to ignition coil terminal 15
Black clip to ignition coil terminal 1.

I'm not going to pretend any of that made sense to me.  I guess I'd try the first connections above if using a dwell meter for non-transistorized igntion systems and see if the reading looks halfway right.  Otherwise, it looks like a dwell meter that specifically works with transistorized ignitions might be the way to go.

One last thought is that point gap and dwell are directly related.  An accurately set gap should give dwell within specs (assuming the distributor shaft bearings are in good shape).  Good luck!

George Davis
'69 280 SL Euro manual

[n/a]

Hi Larry,
I have a generic Sears Dwell Meter with a green wire and a black wire.  The connections are:  green wire goes to pin #7 on the switch box located under the battery tray.  You can use the terminal where the green wire of the condensor attaches.  The black wire connects to ground.
Hope this helps,
Don
71 280sl with transistorized ignition
Cleveland, OH

quote:Originally posted by 71 pagoda

What is the correct way of hooking up a dwell meter to a 71. I was told that you have to attach the leads to the  stock transisterized ignition box under the battery or you wont get a correct dwell reading.
Thanks
Larry
71 280sl  w/transis. ignition

[userzweig]

Don,

Do you need to remove the battery to get to the switch box?  I tried poking around from underneath the car today, and I couldn't figure out how to get to it (late '71 280sl auto).

Bruce

PS - if you do the 2-resistor connection instead, are they accessible from the engine compartment?

quote:Originally posted by Don

Hi Larry,
I have a generic Sears Dwell Meter with a green wire and a black wire.  The connections are:  green wire goes to pin #7 on the switch box located under the battery tray.  You can use the terminal where the green wire of the condensor attaches.  The black wire connects to ground.
Hope this helps,
Don
71 280sl with transistorized ignition
Cleveland, OH

quote:Originally posted by 71 pagoda

What is the correct way of hooking up a dwell meter to a 71. I was told that you have to attach the leads to the  stock transisterized ignition box under the battery or you wont get a correct dwell reading.
Thanks
Larry
71 280sl  w/transis. ignition

1971 Copper 280SL Automatic