Adding a Low Oil Pressure Warning Light to Your Motorhome
September 14, 2010
Filed under Tech Tips
An oil pressure gauge is a great thing to have and most motorhomes are equipped with one.
However, stop and think about how often you actually look at it. The loss of oil pressure
doesn’t take long to do serious damage to your engine, or even seize it, so why not add an
“idiot” light to your coach? A large red light warning you to shut down your engine
immediately could save you from a very expensive repair bill.
I’ve owned two Winnebago
motorhomes, one with a Chevrolet 454 and the current one, a 1997 Winnebago Brave with a
Ford 460 engine. Neither motorhome came equipped with an oil pressure warning light. Adding
one to your coach is a straightforward procedure that can be accomplished by any person who
has at least some mechanical skill and basic tools.
Although your motorhome may be a Class
B or C, and have a different chassis and engine than the one in this article, the basic
installation is the same.
You should be able to complete the installation in less than a
day, provided you have the proper tools and parts on hand (see list of tools and parts
below). It is important to know where the oil pressure gauge sending unit is located on
your engine before you start. Otherwise, with very complicated engines, you could spend a
day looking for it. Here are the locations of the oil pressure gauge sending units for the
most popular V-8 engines:
Chevrolet 454: The oil pressure switch and oil pressure sender
for older 454s are mounted on the lower left front of the engine block just above the oil
Chevrolet 8.1-l: It is on the back of the block just below the intake manifold. It can
be difficult to see and even more difficult to remove. If you have a Class A motorhome with
an inside engine cover, you should be able to get at it easily.
Ford 460: It is located on
the back of the block on top of the bell-housing mount. (My motorhome has this engine.)
Ford V-10 6.8-l: It is located as you sit in the driver’s seat low on the left side of the
engine near the front. Above the oil filter is an oil cooler, and it mounts to an adapter
that mounts directly to the engine block. At the front of the adapter is the oil pressure
OK, let’s start this project, using my 1997 Winnebago Brave Class A with the Ford
460 (7.5-l) engine as an example. Remove the doghouse that’s located inside the motorhome.
It can be unlocked with a blade screwdriver and pulled back out of the way. Now the oil
pressure sending unit can be seen (Photo 1).
Unhook the attached wire and use the Autocraft
Oil Pressure Sending Unit Socket (Part #AC829) with a 3/8-inch drive ratchet wrench and
extension to remove the sending unit. It’s best to work on a cold engine. These oil
pressure sending units and switches require a special socket to remove them, and a regular
socket will not work. I had to loosen a shield attached to the bell housing, using a
5/8-inch socket, to make it easier to remove the sending unit (Photo 2). It was bent for
clearance when the new oil pressure switch was installed (Photo 6).
The sending unit on my
engine has ¼-inch pipe threads, but the new warning light switch has 1/8-inch pipe threads,
so I had to use a reducer. The “T” with both the oil pressure sending unit and the oil
pressure switch looks like Photos 3 and 6.
Screw a 2-inch-long, ¼-inch nipple into the hole
where the sending unit resided. You may need to adjust that length to fit your space,
either closer to or farther from the engine block as needed. Next is the 1/4-inch “T,”
which had the reducer screwed into it, and then the new BWD S397Z Oil Pressure Switch
screwed into the reducer. Lastly, screw the original sending unit into the “T” (Photo 3). Use Teflon pipe tape on all threaded joints. The new switch is normally closed, which
completes a ground when the ignition switch is turned on. This turns on the warning light.
After the engine is started, normal oil pressure opens the switch, which removes the ground
and the light turns off. This is not rocket science.
The oil pressure sending unit that’s
used with the oil pressure gauge is not interchangeable with the oil pressure switch that’s
used with the warning light. The oil pressure switch is just that – an on/off switch.
However, the oil pressure sending unit, working with the oil pressure gauge, reads your
actual oil pressure.
Next, find a place where you want the warning light located. It should
be somewhere on the dash that can easily be seen when you are sitting in the normal driving
position. Be sure to measure twice and drill once (Photo 4).A useless hole in the dash is
a real eyesore. If drilling a hole in the dash is not feasible, auto parts stores or
RadioShack carry a bracket to mount lights under the dash. If you do it this way, be sure
that you can clearly see the light when in your normal driving position.
Find a location
where you can tap into a wire or terminal that is hot only when the ignition is on (See
Photo 5). Run a wire from that location to one terminal of an inline fuse and the other
terminal of the fuse to the indicator light. Then run a wire from the other terminal of the
bulb to the new oil pressure switch (See Figure 1). That’s all there is to it. It might be
overkill, but I soldered all connections and used heat-shrink tubing over all exposed
terminals or any place where a short might occur.
Tools and Parts Needed
- Oil pressure light switch, BWD, Part #S397Z, from Advance Auto Parts, about
- Autocraft oil pressure sending unit socket, Part #AC829, from Advance Auto Parts
for about $9. This is a must-have tool.
- Wire, 18 gauge, from any auto parts store, about $5.50 for 40 feet.
- Terminals: Each installation will be different, but make sure you have the type you
need for your installation to connect to the oil pressure light switch and your source
of 12-volt DC power. Match them up at the auto parts store.
- Heat-shrink tubing to cover any exposed wire or connection.
- Inline fuse holder and fuse. A 5-amp fuse should be more than enough.
- Solder and soldering iron.
- On my installation, I used one ¼-inch “T,” a ¼-inch nipple 2 inches long, and a
¼-inch to 1/8-inch reducer, about $5 from Home Depot. See Photo 3, but your
installation could be all 1?8-inch. If you ask the auto parts clerk to show you an oil
pressure gauge sending unit for your engine, you can see if it is ¼- or 1/8–inch and
go from there.
- Lamp assembly, 12-volt DC, Part #272-0336, from RadioShack, $3.49 for a pack of
two. This is a large, bright light, but you can use any 12-volt DC lamp.
- An electric drill, drill bits.
- A file to enlarge the hole in the dash for the light assembly, if necessary.
- A 3/8-inch socket wrench set with sockets and extensions.
- A terminal crimper.
- Electrical tape.