Issue 30 (June 2015)
MG TD / TF Oil pressure adapter kit
The brake pressure adapter is basically a T-piece that simply replaces the union bolted on the bulkhead that connects the flexible pipe from the block to the pressure gauge on the dash.
With the ignition on, the switch contact closes at pressure P>~20psi and operates parallel to the oil gauge. The switch is connected to a relay and the relay is powered on at P>20psi. The normally closed contact on the relay then de-activates the warning lamp.
Fig 1 – Main kit, comprising oil pressure adapter, sample warning lamps and pre-wired relay module.
Fig 2 – Original oil pressure union. The oil pressure adapter replaces the existing union on the bulkhead.
Fig 3 – Pressure adapter installed and connected. It is mirrored to clear the coil and the copper pipe receives an S-bend.
The relay module (see Fig 1) is pre-wired and mounted in a plastic case which can be fitted behind the dashboard or the scuttle panel with Velcro strips.
The kit includes the wiring from the pressure switch to the relay module. The polished and lacquered warning lamps shown are available as an option.
Fig 4 – Samples of the warning lamp.
This is how it works:
Ignition – ON, engine OFF, no oil pressure, Warning light.
Start engine, when P>20psi Warning light OFF.
Engine ON, p<20psi, Warning light ON.
The warning light stays on until reset by switching off the ignition.
I have also developed a further slightly more complicated module which enables a buzzer to be connected.
When the ignition is switched on the buzzer is off and receives an operation permissive once the engine has been started and the oil pressure exceeds 20 psi. The buzzer going off every time the ignition is switched on would prove annoying. For this reason a test button is fitted to the circuit to enable the buzzer to be tested. This is how it works:
Ignition – ON & engine OFF, & no oil pressure, →Warning light ON & Buzzer OFF
Start engine, when P≥20psi →Warning light OFF & Buzzer OFF,
Engine ON & P<20 psi, →Warning light ON & Buzzer ON.
The warning light and buzzer stay on until reset by switching off the ignition.
This circuit is designed for cars with positive or negative earth.
Fig 5 – Buzzer module undergoing testing.
Fig 6 – Warning lamp combined with indicator lamp.
Declan Burns
Liedberger Weg 6A
40547 Düsseldorf
Tel +49 211 371529 after 5pm.
Email : declan_burns@web.de
Note: declan underscore burns at web dot de
A similar, but much simpler device is described in my article on page 6 of the July, 2010 on-line issue of our club’s “Abingdon Rough Riders Newsletter” (http://abingdonroughriders.org/ARR%20Newsletters/ARR%20Review%20Jul%202010.pdf ).
The relay box can be entirely eliminated by powering the unit from the “dynamo” (D) pole of the car’s voltage regulator, so that it only receives power when the engine is running.
I suggest that readers consult the article before beginning this project.
It would be very helpful if Mr. Burns would disclose his source for the pressure adaptor. It appears identical to the Moss part 760-245 (later MGB) that I used. Unfortunately, this part is no longer available. However, I believe that Moss part 180-090 could be used if the fourth outlet is plugged.
The “Rough Riders” article also presents several other interesting options, including using the horn as a warning device, and incorporating a burglar alarm.
G’day Norman,
I assumed the article “MG TD / TF Oil pressure adapter kit” had to be a tongue in the cheek, joke! Why use a pressure switch that completes the circuit,
as in the brake light application, when an oil pressure switch breaks the circuit and turns off the light without all of the associate wiring and relay module?? The article had to be a joke?
By the way Norman I sourced a MGB pressure switch adaptor on eBay quite some time ago, and everything works just fine, thanks to your article & guidance.
Regards
Graham Hore
Melbourne, Australia
TC 8819
ARR member in Oz.
Norman,
I will disclose the source of the adapter.
My workshop.
Graham,
No it is not a “joke”.
The pressure switch closes at P>20psi which is the healthy desired condition. A closed circuit in the healthy condition is industrial failsafe standard. I deal with such circuits in industrial applications and have been doing so for the last 34 years.
Regards
Declan
Declan: I very much enjoy seeing your clever fixes for those loose ends on a TD, both on TT2 & on the MG BBS T Series discussion forum. Your execution is inspiring too. Keep up the good work!