Circuit Breakers

[RICKG]

KLIXON, SPENCER THERMOSTAT DIV.
I've got (2) of the 7762620 and (5) of the 7760416 that came
in a box with my 51'M-38.
QUESTIONS:
1. There is a letter designation on each ranging from A thru G
on the top of each unit located between the terminals.
Do these letters designate something important as
defined by their usage?
2. Are there different amperage trip ratings on the CBs?
3. Once tripped do they, or how do they reset?
4. My AC instrument panel has the holes for the CB and
the battery box has the holes for the (3) CBs.
I think the 7760416 goes to the inst panel and the 7762620
goes to the battery box. What's the correct set-up here?

Sorry for the long winded post-this is my first shot at wiring a MV.

[wesk]

7760416 is a 15 amp auto-resetting breaker used on M38's before MC65928. You use three on your battery box. Unless you wish to conform to the MWO that moves the bottom one to the firewall so it doesn't get kicked by the big foot guys when they kick the starter pedal.

7762620 is a 15 amp auto-resetting breaker. You use one on the instrument cluster on jeeps before MC65043.

The obvious difference is the size of the Douglas metal connectors.

Purpose of letters marked on the breakers by the manufacturer are not known to me.

[RICKG]

Thx Wes, appreciate it.

[4x4M38]

I'm sure everyone has figured this out, but the 7760416 breaker on the right has the larger Douglas receptacle for the two wire Douglas connector.

Power came into the first breaker from wire #10, then daisy-chained to the other breakers, finally going to the ignition switch on wire #11..

The Douglas 2 to 1 connector is larger than the single wire jobbie. Other than the amperage rating, that is an easy way to visually tell if that breaker goes on the cowl battery box.

Brian

[wesk]

You must still ascertain the breaker's rating before using it. Just because it looks like the right hand breaker illustrated above does mean it has the same rating.

Also make sure you replace breakers with the correct rating. The electrical engineers went through a bit of computing to come up with a breaker that would successfully protect it's circuit based on input voltage, load (current draw in amps) and wiring gauge/length (Resistance). Changing any of these variables will dictate a need to re-compute circuit breaker rating. Using a lower rated breaker in your current system will cause nuisance trips. Installing a higher rated breaker will allow the amp draw to exceed the wiring capability and overheating of the wire and fire will result.

An example of juggling numbers: If you change the input voltage from 24/28 to 12/14 then unless you increase wire gauge (Decrease resistance) you will need to increase the breaker rating. So a complete re-compute of the system using the 12 V component rating in amps, the wire gauge and length (Resistance) and the new input voltage of 12/14 must be done to select the appropriate rated breaker.

Do a little research on the web and arm yourself with information before attempting any changes to the system.

http://www.autoshop101.com/forms/hweb1.pdf

http://www.optifuse.com/PDFs/FuseSelect ... e_RevA.pdf

http://www.allaboutcircuits.com/vol_1/chpt_12/4.html

[RICKG]

Jeez.. so I was wiring my M38 in august of 2011.. seems like forever ago..

[wesk]

The original circuit breakers were produced by Spencer Thermostat Company from 1930 until TI / Klixon bought their product line. Klixon still produces these breakers but only in the more modern form with Packard rubber connector. Adapting the new breakers to Douglass connectors is a simple operation.

http://www.sensata.com/klixon/circuit-b ... reaker.htm

http://www.sensata.com/klixon/circuit-b ... l-9115.htm

Here's their full catalog: http://www.sensata.com/download/klixon- ... atalog.pdf

The 15 amp breaker is:
9115-5-15 for auto reset
9115-6-15 for manual reset.


This is the 9115 series.

Here's a list of regional US offices you can call to get local dealer info:
http://www.sensata.com/contact/business_centers.htm