Thursday, December 24, 2015

Fuel Gauge Replacement

It's been a while since I did a how-to post. I guess I'm overdue. Here is a step-by-step for installing a new fuel gauge that I did over my winter break (see: Planning Winter break). This is not about installing a new tank-float. That's documented pretty well around the internet, with 2 main options: pull the engine, firewall and tank -or- cut a hole above the tank and put in a maintenance port-hole.  I've seen lots of accounts from folks who have replaced their tank float, and I think that's because that's the most common cause of fuel gauge failures. Before I did the engine swap, I lost the use of my fuel gauge. So, when I pulled the tank to get cleaned, I tested it. It wasn't the cause. After waiting a long time, I finally found a gauge that looked like the original (original look available from Cip1). So, on with the new gauge.

This should go without saying, but when you get down to swapping out stuff that is electrical, or if you're messing with stuff that's near other stuff that is electrical, pull the ground off the battery. I left mine attached a little too long (I spent some time testing the old and new gauges to make sure the old one was bad and the new one acted differently), and blew a fuse. Duh.

Pull the Dashpod
The VW bus dash is held on with 4 Phillips-head screws, but first that's not where we start. First, reach around the back and unthread the speedometer cable. Next, pull the little plastic bits off the ends of the fresh air and heat controls. My bus doesn't have those, but I've heard they can be stubborn and break easily. There are replacements on BusDepot, if you break any. Now, remove the 4 screws. Starting on mid-year bays, there are little clips on the backside, and those can bounce pretty far when the screw comes out. Put your hand back there as you remove the screw and catch it. Once the screws are out, the air controls are free and the speedo cable is detatched, there's nothing holding the pod in to the dash. Lift it a couple of inches and then tip the top down under the steering wheel. You can do this job without moving anything much farther than this. Zip-lock baggy the 4 screws and label it. You may intend to come back to the job right away, but jobs get interrupted.

Remove the Back
The rear panel is held on with 6 hex-screws (6mm). Righty-tighty. Lefty-loosey. Easy Peasey. Like the 4 in the step above, stow the screws in a zip-lock baggy. The metal rear panel wants to stay attached because of a little lip that runs around the edge of the plastic housing. Pop the metal panel off and set the plastic housing aside. The brake idiot light wiring will prevent you from moving it too far, but there isn't that much room under that steering wheel, so any inches are worth it.

Loosen Fuel Gauge
Circled in red in the picture (and on the back of your dashpod), you can see a small bolt. That bolt and the two tiny brass buttons on either side of it hold the fuel gauge to the metal rear panel. The "nut" doesn't have any flat sides to it, so you need to crack it loose with a pair of pliers. It has a couple slots on either side, implying there's some obscure VW (or VDO) tool to remove the nut. Pliers work fine; it's not torqued much. Under the nut are 2 washers. Put them together into a zip-lock baggy and label it.

Free the Face
On either side of the center of the front of the gauge, there are 2 tiny slotted bolts. You will need a tiny slotted screwdriver to remove those, but once removed, the grey face can be removed. Those bolts are tiny. They will sail and disappear if you aren't really careful with them as you remove them. Like all the other fasteners, put them in a zip-lock baggy. Hold the dashpod as level as you can and lift the face directly upward. Under the face, you will find colored plastic blocks for the turn signals and idiot lights. I'd thought they were simple gels, very thin and hard-attached. They're actually quite thick, almost as thick as a lego, and they will fall out if you tip the dashpod. Ask me how I know :)

Gauge Swap
Now that we have all the dash stuff out of the way, we can get down to it. Gently lift the old gauge out of the pod and unplug the tiny clips from the signal and switched-power. The lower corners need to be negotiated around the bolt holes. The new one (from Cip1), fits in as well as the old one, requiring some wiggling to get it in place. The colors of the wires on the new gauge aren't consistent with the original. The green goes to signal and the red goes to switched-power. Make sure the bolt fits through the hole in the metal rear panel, and the gauge is behind the bolt holes.

After the gauge is in place and wired, get the gauge face back on next. The main motivation here is getting the face on before the color plastic bits fall out. Again, ask me why :) The bolts can be tricky, even if you have small fingers. They don't need to be torqued down terribly hard, just snug. I tightened until snug and then just enough to make the slots level. Yeah, that's a little OCD, but whatever. Now, you can put the 2 washers on the bolt-post sticking out the back and thread the round nut onto it. In my case, I added another grounding wire at this point running off this post. Finger tighten and then snug with pliers. Next, attach the rear metal panel to the plastic housing with the hex screws (6mm). Before you install the dashpod back into the dash, double check that there aren't any loose wires, and verify your grounds. Then, slip the dashpod into place, screw in the 4 Phillips head screws, and put the air control knobs back on. Reach around the back and thread on the speedometer cable. Last, re-connect the negative cable to the battery.

In my case, the fuel gauge wasn't actually the problem. I did all of the above and the gauge still didn't work. I found that the gauge ran to Full (1/1) when connected and hanging loose (ungrounded), but as soon as the gauge was grounded by mounting it to the metal rear panel, it fell to 0/1. Concluding the thought-to-be-good float/sender was the culprit, I went to the rear of the bus and tested the resistance on the float: 49.5 ohms or 1/2 full (range from 100 - 0 ohms 0/1 - 1/1). So, the sender is good, the gauge is good. This leaves the wire as the problem. I'll post on that another day (after I've fixed it). In the meantime, I put the original gauge back in: Aint Broke, Don't Fit It.

That's it for today. Thanks for following along...

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