One of the first things I did to awaken my car from its’ 15 year hibernation was to replace the fuel tank as the original tank was full of 15 year old gasoline. The new tank included a replacement sending unit for the fuel gauge. I thought the old sending unit was probably in very bad shape so instead of removing and keeping it I discarded it along with the old tank and fuel. It turned out that might not have been such a good decision.

I quickly discovered that my gas gauge wasn’t very accurate anymore. Not that it ever was that great. But now it insisted I had a quarter tank left when I was only about half a tank low. It turns out the new sending units don’t match the factory gauges. I believe the sending unit is fairly linear, but the factory gauge isn’t. So full and empty match up fairly well, but readings in between are off. If I had saved my old sending unit it would be a lot more accurate.

After some research online I found a post containing resistance measurements that compared an original sending unit and a replacement sending unit. Here is an excerpt from the post I found on the Vintage Mustang Forums. I rearranged the resistance readings into a table to make them easier to compare.

These were bench measurements so they are based on swing of the sender which may not be exactly at the tank measurements.

Reading	New Sender	Original Sender
Empty	74	71
1/4	60	36
1/2	42	22
3/4	23	15
Full	8	9

You can see that the new sender is roughly linear between positions (15,19,18,14) while the old sender is not (6,7,14,35). This is why the new senders drop the reading to empty very quickly then stay there.

One very smart poster on the VMF by the name of Woodchuck suggested using an Arduino to map between the linear and non-linear values. It turns out that somebody has already done something similar. It’s from the company TechnoVersions and is called the Meter Match. I purchased one online and it arrived within a few days. Here is a picture of the Meter Match with some connectors I added as a part of my wiring project.

I wanted to build a wiring harness for the whole mess so that I could service the instrument cluster by simply unplugging the unit. I also needed to be able to reach the Meter Match so that I could calibrate the gauge without requiring access to the back of the instrument cluster. I chose to place the Meter Match in the console storage area. Another place for it could be in the glove compartment. I ordered some connectors and colored wires to build the harness.

I have a spare instrument cluster so I decided to test the gauge on my workbench with and without the Meter Match in an attempt to characterize the gauge’s behavior. This would permit me to test the Meter Match and perform an initial calibration before I installed everything in the car. Below are the results of my characterization. One thing to note is that the stock instrument cluster voltage regulator is about 5 volts. The meter match has a built in regulator that supplies the fuel gauge 8 volts. The fuel gauge behaves differently depending on whether it receives 8 volts or 5 volts. I characterized the gauge using both voltages with no Meter Match, and with 8 volts using the Meter Match.

Resistance (Ohms)	No MM (5V)	No MM (8V)	MM (8V)
10	F	F+	F+
15	3/4+	F+	F
25	3/8	F	3/4+
27	1/4+	7/8	3/4
42	1/4-	1/2	1/2-
50	1/8	3/8	1/4
60	E+	1/4-	1/8
65	E	3/16	E
75	E	1/8	E
77		1/8	E-
82		1/8

From this chart I can see that if the sending unit behaves in a linear fashion the MeterMatch should get my gauge fairly close even before I calibrate it in the car. The readings I got also match up fairly well with the posting on VMF for the original and replacement sending units. Now I need to get to work removing the instrument cluster and doing some wiring. I plan to power the MeterMatch from the accessory post of the ignition switch. I also plan to add a fuse in the +12V wire for safety. Since the tank is already fairly full fine tuning the calibration will take quite a bit of time and plenty of trial and error. My next post should be the final installation and testing. I will try to post again after the end of the 2019 car show season to talk about my calibration efforts.

In 1967 the Mustang didn’t have anything to catch coolant overflow. It just dumped any excess coolant onto the ground. That may have been OK in 1967, but today dumping coolant on the ground is heavily frowned upon. I experienced this first hand when I slightly overfilled my coolant, drove on the highway for 30 minutes, and then stopped at a gas station to fill up the tank. The excess coolant ran out onto the ground which caused quite a stir with the people watching me fuel the car. I was told my car had a serious coolant leak that needed to be repaired right away. Explaining about the car’s lack of any coolant overflow catch can only resulted in very puzzled looks. The best (and most environmentally friendly) solution was to retrofit some form of coolant catch can.

I did some research online but couldn’t find a catch can or recovery system that blended in with the engine compartment the way I wanted it to. This was discouraging because I didn’t want something that really stood out. After plenty of measuring and research, I chose a stainless steel catch can which I purchased on eBay. Here is a picture of what I purchased.

To install the catch can I made up an L shaped bracket using some sheet aluminum. I drilled holes on one side of the bracket to line up with my fan shroud mounting bolts and two holes in the other side of the bracket for the catch can. I put some weatherstripping between the bracket and radiator just in case the bracket rubbed on the radiator. Then I bought some neoprene tubing to go from the radiator overflow to the catch can. The end result does stand out a little more than I would like, but overall I’m OK with the modification.

Another show season is over. I attended far fewer shows this past season, mainly due to the wet and rainy weather. I did get to spend some time at the shows I did attend with my good friend Randy. We have a lot of common interests, so we never seem to run out of things to talk about. Other than cars, we also share interests in ham radio and photography. Randy is usually building something and I always like to hear about what his next project might be.

This winter I hope to be able to tackle some nagging issues on the car. I feel that most of the door locks/handles and window mechanisms could use some more fine tuning adjustments. They all work, but not as consistently as I would like. The driver’s side seat back could fit a bit better. The gas gauge is pretty inaccurate due to the replacement sending unit. I want to install a coolant overflow, even though the car never came with one. And finally I may choose to install a subwoofer. But I haven’t completely made up my mind on that upgrade yet. It just might be convenient to do it at the same time I take apart the interior for the other upgrades.

Everything I mentioned above is optional and I may or may not have the time and motivation to complete the jobs. As of now I already have the coolant overflow and gas gauge calibration parts on hand, so I hope to at least complete those two jobs. How much else I get accomplished will depend on the weather, my mood, and my health.

As far as car shows next season goes, I plan to attend some of the larger shows that I may have considered too far away in the past. I probably won’t make it to all of them, but here’s my tentative list so far. Some of the dates haven’t been set yet, so I plan to update this list as more information becomes available.

Name/URL	Date(s)	Location	Distance (One way)	Travel Time	Comments
Romancing the Chrome	4/13/2019	Jarrettsville, MD	73.3	1.5 hr	Over 300 cars
Cruisin’ Ocean City	5/16 – 5/19/2019	Ocean City, MD	167	3 hr	Approx. 3000 cars. Lots of cars cruising.  As seen on the Lokar Car Show
Street Rod Nationals East	5/31 – 6/2/2019	York PA	88.6	1.6 hr	Approx. 3500 cars
Liberty Street Rods Rod Run	6/23/2019	Sykesville, MD	28.7	45 m	Over 300 cars
Frederick MVA Alzheimer’s Car Show	09/15/2019	Frederick, MD	24.6	32 m	250-350 cars
Mobtown Greaseball	09/21/2019	Sparrows Point, MD	56.4	1 hr	400-500 cars.  Great name for a show. Looks like plenty of customs and rat rods.
Charles Town Car Show	Sep-19	Charles Town, WV	47.6	1 hr	Over 600 cars
Ridgely Car Show	09/22/2019	Ridgely, MD	89.7	1.6 hr	Over 800 cars – On My Classic Car TV show
Rockville Antique and Classic Car Show	10/19/2019	Rockville MD	11.3	21 m	Over 600 cars