Added a gauge cluster...

[Donald Watson]

Ryan,

Nice job on the engine compartment gauge cluster, especially the switched
back lighting. A mechanical oil pressure gauge makes sense. I didn't find
mention of 'parallel gauge' issues in previous posts leading up to the one
I'm responding to. If you weren't already aware of it, electrical gauges
are resistive devices. When you stack one on top of the other, such as two
identical water temp gauges, the parallel resistance of the gauges is now
half what the sending unit was designed for. The result can be an erroneous
gauge reading sometimes twice what it should be.

To take this into account, you either have to have two separate sending
units or a sending unit specified as handling two gauges. That special
sending unit can only be used with two gauges and not one. If an additional
water temp sending unit is installed, it is important to have it located
where it will give an honest reading of engine coolant temperature; just any
threaded plug in the coolant system might not be appropriate. Another issue
is the location of a coolant temp too high in the system. If the coolant
level falls below the sensor, it will no longer be reading coolant temp.

Newer engines incorporate warning indicators and some auto shutdown
procedures. Older engines may include after-market alarms for high coolant
temperature or low oil pressure, but the later is tricky on two cycle
Detroits that might exhibit as little as 8 lbs at idle, but still be
healthy. Alarm sensors (switches) are a topic for another discussion.

Gauges, got to have them. Even better, training the eye to scan them
regularly while driving.

Regards,

Donn
76 FC33
South Kingstown, RI



From: WanderlodgeForum@yahoogroups.com
[mailto:WanderlodgeForum@yahoogroups.com] On Behalf Of Ryan Wright
Sent: Thursday, October 23, 2008 11:04 PM
To: wanderlodgeforum
Subject: [WanderlodgeForum] Added a gauge cluster...

...& my oil pressure is just fine, folks. Mechanical unit verified
60lbs at startup. The sending unit for the front gauge is shot. I'll
get a new one ordered in the morning.

In the meantime, I added a cluster of three gauges in the back of the
coach tonight:

http://www.ryanwright.com/tmp/eng-gauge1.jpg
http://www.ryanwright.com/tmp/eng-gauge2.jpg

They look real purty all lit up. I've got a mechanical oil pressure
gauge on the right, volts in the center and coolant temp on the left -
haven't hooked the coolant temp lead up yet, though. Still trying to
figure out how to go about that one. Anyway, they're tied into the
rear lighting so they only come on with the engine door open. This was
a pretty easy project once I found that oil pressure sending unit.
Cost me all of forty bucks and will come in real handy when doing any
sort of engine troubleshooting.

Huge thanks for all of the advice on that sending unit.

-Ryan
'86 PT-40 8V92