testing/replacing low fuel relay
#1202954
03/25/12 01:35 AM
03/25/12 01:35 AM
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Irving, TX
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Irving, TX
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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?
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: testing/replacing low fuel relay
[Re: feets]
#1202955
03/25/12 01:44 AM
03/25/12 01:44 AM
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1_WILD_RT
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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
Last edited by 1_WILD_RT; 03/25/12 01:46 AM.
"The Armies of our ancestors were lucky, in that they were not trailed by a second army of pencil pushers."
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Re: testing/replacing low fuel relay
[Re: 1_WILD_RT]
#1202956
03/25/12 01:56 AM
03/25/12 01:56 AM
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Irving, TX
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Irving, TX
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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.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: testing/replacing low fuel relay
[Re: feets]
#1202957
03/25/12 02:00 AM
03/25/12 02:00 AM
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1_WILD_RT
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They all fail, an NOS ones gonna fail too, just jumper the IVR power to your fuel gauge...
"The Armies of our ancestors were lucky, in that they were not trailed by a second army of pencil pushers."
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Re: testing/replacing low fuel relay
[Re: 1_WILD_RT]
#1202958
03/25/12 02:14 AM
03/25/12 02:14 AM
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Joined: Jan 2003
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Irving, TX
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Now I need to find the secret to speedy and non-violent Fusey dash removal.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: testing/replacing low fuel relay
[Re: feets]
#1202959
03/25/12 02:31 AM
03/25/12 02:31 AM
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1_WILD_RT
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Power screwdriver & lower the column then disconnect the speedo cable... I had the dash out of my pops 73 dozens of times..
"The Armies of our ancestors were lucky, in that they were not trailed by a second army of pencil pushers."
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Re: testing/replacing low fuel relay
[Re: 1_WILD_RT]
#1202960
03/25/12 02:41 AM
03/25/12 02:41 AM
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Irving, TX
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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.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: testing/replacing low fuel relay
[Re: feets]
#1202961
03/25/12 02:47 AM
03/25/12 02:47 AM
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1_WILD_RT
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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...
"The Armies of our ancestors were lucky, in that they were not trailed by a second army of pencil pushers."
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Re: testing/replacing low fuel relay
[Re: 1_WILD_RT]
#1202962
03/25/12 12:38 PM
03/25/12 12:38 PM
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Irving, TX
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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.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: testing/replacing low fuel relay
[Re: feets]
#1202963
03/25/12 04:19 PM
03/25/12 04:19 PM
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Joined: Jan 2003
Posts: 21,065
Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,065
Niles , Ohio
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I might have one of those in the other garage.I had 3 Imps that I striped and they all worked.Rocky
Chrysler Firepower
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Re: testing/replacing low fuel relay
[Re: feets]
#1202964
03/25/12 04:34 PM
03/25/12 04:34 PM
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Joined: Jan 2003
Posts: 4,587
St. John's Newfoundland
440newport
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master
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St. John's Newfoundland
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Quote:
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.
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.
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Re: testing/replacing low fuel relay
[Re: 440newport]
#1202965
03/25/12 05:08 PM
03/25/12 05:08 PM
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Irving, TX
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The cluster came out last night.
After finding all the screws, it was a matter of moving the panel a wee bit and finding the next harness to unplug.
I didn't unplug the headlight switch. Instead, I pulled the knob off and left the switch in the car.
The upper speedo cable is shot so I picked up a new one today. I think I'll leave it off the cruise servo until after the cluster is installed.
One thing I'd really like to find is window switches. They're specific to the Fusey Imperials. A couple of mine have broken toggles and I'd like to replace them.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: testing/replacing low fuel relay
[Re: feets]
#1202966
03/25/12 07:28 PM
03/25/12 07:28 PM
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Joined: Jan 2003
Posts: 4,587
St. John's Newfoundland
440newport
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St. John's Newfoundland
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Quote:
One thing I'd really like to find is window switches. They're specific to the Fusey Imperials. A couple of mine have broken toggles and I'd like to replace them.
www.arizonaparts.com might have them. I got some p/w switches and some other things for mine there. They have a mix of NOS and nice used parts. It can be a bit of trial and error to find stuff on the list if you don't know the part number, but the prices are very fair.
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