Hello, I am restoring a 1983 Chenowth Fast Attack Vehicle FAV Buggy as used by the former 9th Infantry Division on Ft Lewis, WA. These highly modified Chenowth 4LWC dune buggies used high performance air cooled VW Boxer 1984cc engines built by Don Hatz. The 9th Inf Division was known as the High Technology Test Bed unit the conventional Army used to test these mobility platforms that went on to be used by Navy SEALs and USMC Recon. They fielded the first "Blue Force Tracker" type devices, ground located laser designators for air strikes, etc, with doctrine of fighting at night with the AN/PVS-5 NVG. The idea for the Chenowth dune buggies came from Emerson Electrical Engineering who had a contract for remote controlled target drones for the Navy. They modified Chenowth 2RW/2LW chassis buggies with the VW 003 Autostick Transmissions and a box full of servos, for the Drone to be dual control, able to driven by a human long distances out to the target range, then switched over to RC for the Navy to attempt to hit them with naval gunfire.


In order to try to protect these engines from the 17-19 year old Privates who would be driving them an Engine Protection System circuit board was made to automatically kill the engine when the cylinder head temp CHT reached a certain point, likely somewhere around 350-400 degrees F. This EPS did have an Emergency Ignition System that allowed the crew to override the kill switch if needed in combat.
On the 9cm x 6cm faceplate there is a 12vdc alarm buzzer in the center to emit an audible alert the engine is overheated. There are also two 5mm bezel amber indicator lights, one in the lower left to indicate the Overheated status, the other in the upper right that lights when the Emergency Ignition System toggle switch is turned on. Then on the lower right a waterproofed micro toggle switch SPDT 6 pin soldered to the board. There is a 44mm x 68mm hole in the dash for the EPS circuit board to pass through.

Main component is Potter Brumfield R50.-E2.Y2 12VDC DPDT Relay.
Solder footprint for 6 pin SPDT micro 1/4" toggle switch
There are some resistors used on the board.
4 place terminal block, like the Uxcell 4 position 11mm pitch 300v 20 a terminal strip.
Amber indicator lights back then were incandescent, but for my purposes the Blue Sea Amber 8033 Indicator LED are contemporary substitute.
The FAV dashboard has a VDO 85mph speedometer; 18v Ammeter; 70 PSI oil pressure; fuel gauge; and a VDO 310-901 Cylinder Head Temp Gauge which uses a K-Type VDO 323-701 14ft long thermocouple 14mm ID terminal under one of the spark plugs, unknown Ohm.
I don't know if the CHT Thermocouple is part of the EPS circuit.
I think it would be safe to assume the main starter switch power passes through the EPS so the micro toggle switch should be an On/On type, the "Off" position being the ON for the main starter power from rotary starter switch to the coil.
Any assistance would be greatly appreciated. There are several of us, like 6-10 who would be able to use these EPS boards for personal use, vehicle collector purposes, not commercial.

 

Any assistance would be greatly appreciated. There are several of us, like 6-10 who would be able to use these EPS boards for personal use

Not clear on what you want.
Do you need to determine how the board works and how it should be connected to work in a vehicle?
That would require a lot more detail about the board's internal connections.

 

I can't tell what the EPS sensor is.
A thermocouple signal is small, quite low voltage. Type K output at 450°F/232°C is only 0.0094V so some electronics is needed to amplify that.
I'd expect some inside the VDO gauge. But I don't see anything in the EPS board pic unless it's on the other side of the board? It's more likely a high temperature switch located on the engine head, for that era.
Or a millivolt thermopile like used in older water heaters but it that still needs a special relay.
But the R50-E2-Y2-12V relay appears to be vanilla, nothing special. Possibly NSN 5945-01-288-4753

 

I'm trying to get more photos of the components on the board underside.
Alternatively, how would I go about creating a similar function circuit using contemporary components but keeping an identical faceplate? Example a 350 deg F snap switch that opens at temp to kill the coil power, lights the Blue Sea 8033 Amber LED "Overheated" lamp, and, activates a 12VDC alarm buzzer?
DPDT 1/4" micro toggle switch to switch to the alternate Emergency Ignition System and lights the other Blue Sea 8033 Amber LED "Emergency Ignition System On" lamp.

 

Certainly a non-millitary control system will be easier to work with. BUT ifthe OEM system works that would be a great starting point.

 

If the head temperature sensor is a type "K" thermocouple then the output at 350 degrees is still not very much. It is not clear to me if there is a head temperature meter display, or just an over-temperature cutoff relay.
CERTAINLY there is a bit of amplifierto boost the "K" TC output. A cheap and simple alternative will be a Snap Disk thermostat set to trip at 350 degrees, attached to the hottest head bolt. For the head temp display, those are commercially available, and very well documented. And probably rugged enough to survive NON-BATTLE use. That switch to bypass the safety used to be called a "battle-switch", they were also used to bypass fuses in some comm systems, back in vacuum tube radio times. For non-tactical uses a temperature gage is a very good choice, because an excessively overheated head CAN LEAD TO a "very abrupt" engine failure mode that is not only expensive to repair but usually "rather inconvenient". (to use polite terms)