testing/replacing low fuel relay

Before I screw around and let the smoke out of this thing, Does anybody know how to test a low fuel relay?

Andrewh and I went off the deep end tonight and spent a few hours ripping the cluster out of my 72 Imperial. The gas gauge wasn't working and all the typical tests failed.

Bench testing shows that the gauge works great.

Chrysler cut the circuit board to prevent power leading to the fuel gauge. A look at a wiring diagram shows power coming from a low fuel relay.
This car has a Check Gauges light that comes on with low oil pressure, high temperature, and low fuel level.

The relay draws power directly from the fuse block. It sees 12 volts. It has another lead going to ground. The last two leads hit the fuel gauge and the check gauges light.

A 3 volt bench test had the fuel gauge running a little more than half it's range. That tells me it's a 5 volt gauge like the rest of them.
Shooting 12 volts off the fuse block would probably let the smoke out of the gauge.
I can only assume the relay reduces power to 5 volts for the gauge.

If that's the case, how does it turn on the check gauges light?

If this relay is dead, where would I find another one?

It acts as the IVR for the fuel gauge, you could bypass the low fuel warning & jumper the connection from one of the other gauges power side to the fuel gauge power post... Basically the relay looks at current flow & when the fuel sender resistance gets high enough the relay closes & powers the low fuel lamp circuit.... NOS relays pop up on ebay occasionally. Fact is currently there are three, this is the cheapest..

http://www.ebay.com/itm/NOS-Mopar-1970-7...tr#ht_500wt_922

Thanks.

I guess if the relay is dead I won't have a low fuel light.

$125 for the relay? No thanks. I'll pass.

They all fail, an NOS ones gonna fail too, just jumper the IVR power to your fuel gauge...

Now I need to find the secret to speedy and non-violent Fusey dash removal.

Power screwdriver & lower the column then disconnect the speedo cable... I had the dash out of my pops 73 dozens of times..

We lowered the column but had a horrible time trying to get to the cable.
In fact, we had a hard time getting to most of the stuff in there.
The factory manual offered hints but that was it.

You could cheat & disconnect the speedo cable at the Cruise Servo which would allow the dash to pull out a few inches so you could easily disconnect the cable at the speedo...

Getting the cluster to move forward at all was a real trick.
You have to lift it up and roll the bottom out first.

Most annoying.

I might have one of those in the other garage.I had 3 Imps that I striped and they all worked.Rocky

Quote:

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Getting the cluster to move forward at all was a real trick.
You have to lift it up and roll the bottom out first.

Most annoying.

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Did you get it out? I found it was easiest to let the speedo cable go from the cruise servo and push it in a few inches.
Loosen the radio and let hang down.
Watch the gear indicator as you drop the column, it may want to jam up in the cluster. The wires for the headlight switch and some other things are a bit short, it's kind of a trick to unplug some of that stuff as you pull the cluster out.

The Imp cluster is a little different, but I've had my 73 NY dash out a few times.