how to pass through firewall for aftermarket gauges? ('93 Fleetwood)

[dochawk]

I may be asking something that the instructions for the gauges could tell me, but I don't see how they could cover all models . . .

To run aftermarket gauges, how do I pass the signal wires from the engine compartment to the passenger compartment?  Are there knockouts to use, or room with another wire group, or . . .

[Abe Lugo]

If you are using aftermarket gauges you can see if there are any fire blanks that can be knocked out near the are you need to go to turn add a universal rubber grommet that is a blanked, then cut the proper sized hole.

[fishnjim]

I always try to use existing grommets and pass throughs, and take a straightened coat hanger or similar(fish tape) with a small hook on the end to tape the wires to and push from outside to in then, pull from the inside out.  If more than one strand, tape them in a bundle so they don't catch.
It's easier and neater than drilling more holes and installing new grommets, but whatever you find you prefer.
For things like voltage, you can tap under the dash from a hot wire to ignition or elsewhere that's always hot.  Some oil gauges have a tubing so I don't like those style.   Tach is to the coil, so need to use a thermal covering on that one or any, water temp or oil pressure, over the motor.  Any of the auto wire supplies carry in many sizes.  Wiretek, Del City, etc.
Likely spots around the steering column and where the harness goes inside.  Depending on the vintage, it maybe just some sealant around the hole and wire.  Best to stay out of vents and under the floor as those are wet areas.
I tend to leave the vacuum and fuel pressure under the hood, because you only need those when your working on it.

[dochawk]

I absolutely want coolant temperature, as I'm doing battle with the fans (but hope to win today, or at least pinpoint the problem to which side of the primary relay).  Oil pressure would also be good.

Tach and voltage would be nice, but not so critical (although I suppose voltage would have told me that my battery *wasn't* undercharged).

I'm also thinking to run two lines for LEDs to show whether or not the fans are running.  That the second one went out between when I found the first one not running and when I started probing makes me nervous . . . (the other replacement morning is sitting up the street waiting for me to pick it up)

[dochawk]

hmm.  I'm just not finding many grommets.

THere's one for the accelerator cable, and I found another huge block going in under the glove compartment.  Also, the heater water line, but that would be a really bad idea . . .

[The Tassie Devil(le)]

The big problem is that these later model cars have far tighter bodies and the designers thought it best to have the least areas for the outside to leak into the insides.

You might simply just have to bite the bullet and select a pace to best gain access through the firewall, considering both sides, and drill the required hole in the metal to accept the correct size rubber grommet to seal both the wiring, and the hole.

Bruce.    

[dochawk]

I'm shuddering at the invitation to rust that that would be . . . [and nervously looking over my shoulder for hit squads from the authenticity wing . . . ]

[The Tassie Devil(le)]

Well, wouldn't the adding the gauges also cause panic amongst the Authenticity wing?

The trouble these days is that things like Speedo Cables are now part of the electrical circuitry.

Including extra cabling in a wiring look most probably won't work, as the loom would most probably go through a bulkhead connector, with no free plugs/terminals.

One day, maybe WiFi connectivity will become available with new units.

As an aside, one would have to be careful where to mount the gauges as it might create a problem with the internal safety in relation to non-standard options causing damage in the event of a crash.

Bruce.

[harvey b]

I did a similar thing on a chevy truck,i was able to pop out the grommet for the hood release cable and use that hole,i was just running a single wire through . harveyb

[The Tassie Devil(le)]

Oops, I forgot about the Hood Release cable.   Most cars still have these.

Bruce.

[dochawk]

the wifi options have a lot of appeal for me.  I can build those, and could have a custom display.

But I sure want something temporary after yesterday's drive and jury rigging toggle switches instead of fan relays, I sure want an interim temp gauge . . .

Or, I suppose a monitoring computer under the hood connecting by a single wire to a display computer in the passenger compartment.  I'll have to use a different microcontroller under the hood than I usually would, but I understand that there is an automobile rated variant.

As for authenticity, I *try* to do things in a way that can be removed, preferably in a way that can quickly be removed and reinstalled.  One of our members fit a starter to his '03 that mounts and unmounts to existing posts and uses a belt.