I need a map of my Detroit Diesel!

Gordie Allen · January 17, 2013, 04:40:45 PM

I'm wiring up a new dash from Custom Instrument Panels on my 4104 ("The Bus" on the Projects forum). It has a DD 671 inline. I've got all the switches wired (ON/OFF, Start, Reverse, High Idle and all the lights). I'm starting on the gauges and telltales. I can't identify the old oil pressure sending unit. There are a number of sending units on what appears to be a water jacket mounted above the injector rack cover, but none look like the new unit I have. Some have wires attached, some don't. I can't find any other sending units on the engine. Can anyone help me identify the oil pressure and water temp sending units?
Thanks,
Gordie

Cary and Don · January 17, 2013, 05:27:05 PM

You may not need to know where they are coming from in the back. When we did our 4107 we attached to the driver electrical panel up front for all our wiring. You will need a wiring diagram for your bus though. You also have to be very careful as to what somebody else may have changed along the way. It took a month of weekends to get the new dash wired up.

Don and Cary

Gordie Allen · January 17, 2013, 07:12:48 PM

I was lucky.. The bus came with the original manual with complete wiring diagrams. I've removed ALL of the original wiring up front (too old and unreliable). So, I gutted the driver's panel, put in a new white panel board, new fuse blocks, circuit breakers, and new junction buses. I kept the old relays in the back until we got the engine running from the new dash, then replaced them with modern relays with spade connectors. Installed a fuse block in the rear electrical panel. It can now be gutted and rebuilt now that the engine management components (on/off, reverse, high idle, etc.) are functional. 80% of old wiring was unnecessary, like original passenger lighting system, air conditioning wiring, and "idiot driver" shutdown system. Were any part of that system to fail, I'd be a month tracking down the what shut my engine down. I'd rather be an attentive driver, than stranded by an old "fail-safe" system. I've rewired the dash heater motors as well as the BIG coach heater motor. Had to take the dash heater motors apart and shrink wrap the wires as the original covering had rotted away to bare wire as it passed through the housing. The only original wiring I'm keeping is the primary battery cable that takes power to the driver's panel. Original wire from back panel remains for now and oil pressure wire is located on post 15 according to the manual, but I have to rip the taped wire loom apart to trace that wire. Just thought the forum would save me the hassle.

gus · January 17, 2013, 08:04:15 PM

I don't really understand what original wires you have left but basically you need to check resistance between the disconnected wires on the old gage to the wires from the senders at the engine - or to the correct drivers elect panel post. The one not infinity is the right one. Any wire will do since you have disconnected the alarms.

PCC · January 18, 2013, 07:25:49 AM

Having worked in the communications industry for many years, we use a tester known as a "toner". You attached the clips at one end and the inductive unit found the correct wire at the other end.

I have used this when tracing a break in a wire, or trying to identify which wire goes where.

One thing is that you need to be sure the wire is not powered while testing.

Gordie Allen · January 18, 2013, 07:55:04 AM

Gus/PCC
Good idea. I should be able to use a multi-meter to test continuity from post 15 to each sending unit. Whichever one shows continuity is the one I'm looking for. Thanks!

The photo below shows all the sending units I can find.

siberyd · January 18, 2013, 01:51:44 PM

Gordie,

Can you share a picture of the new instrument panel. I will have to change out some stuff eventually too.

Siberyd

Len Silva · January 18, 2013, 02:06:02 PM

It appears someone has added an extra sender in place of the vent cock.

gus · January 18, 2013, 02:38:46 PM

As Len has clearly shown, this is the water temp gage sending housing, not the oil.

As I remember the oil manifold with sensors is much smaller and up higher mounted to the firewall.

Gordie Allen · January 18, 2013, 04:07:07 PM

siberyd,

Here's a couple a pix.

Gordie Allen · January 19, 2013, 06:04:58 AM

After reading Gus's post I found the sending units in a couple of minutes. Right in front of my nose! And, I've been looking for a week. Tucked up in the left corner under the reserve cooling tank. Thanks to all who replied.
Gordie