Mercury Cougar Owners banner

1 - 12 of 12 Posts

·
Registered
Joined
·
1,853 Posts
Discussion Starter #1
My fuel solenoid or sending unit seems to work well however the low fuel light does not seem to work. I actually tested it out of the tank. No light. I have seen sending units for sale but never an XR7 with the low fuel light. What can I do about this?
 

·
Premium Member
Joined
·
13,577 Posts
Buy one of my ELFI kits and use it with a standard sending unit or a LF sending unit with a good gauge sender, either will work. $110 shipped in the US.

Available for 67/68 and 69/70 (which should also work for 71-73).

Regards,

Bob
 

·
Registered
Joined
·
2,739 Posts
On rare occasions I see an nos thermistor for sale. I believe JCC still offers a service to rebuild your old thermistor. I am using a JCC rebuilt unit now and have been for about 7 years and it is still working. Bob's solution sounds like a good one as well.

There are other thermistors out there, used by other auto manufacturers so if one were knowledgeable about such things they may be able to find a replacement using one of the new thermistors available.


My fuel solenoid or sending unit seems to work well however the low fuel light does not seem to work. I actually tested it out of the tank. No light. I have seen sending units for sale but never an XR7 with the low fuel light. What can I do about this?
 

·
Registered
Joined
·
5,633 Posts
A search of old threads will reveal the correct thermistor. The big caveat is that the thermistor is just the first thing you need to fix in most cases. There is also a resistor ballast wire that is frequently bad and also the relay is notorious for failing. You might get lucky and just do the thermistor, but you might end up spending at least as much as the solution Bob has developed. or more trying to get it to work.
 

·
Registered
Joined
·
1,853 Posts
Discussion Starter #5
1969XR7Vert, tell me more about the ELFI you are talking about. and these resistors or balist that XR7G428 was talking about?
 

·
Registered
Joined
·
267 Posts

·
Premium Member
Joined
·
1,276 Posts
I thought they sometimes disconnected that thing on the assembly line beacuse of it lighting up too often on turns?
 

·
Premium Member
Joined
·
328 Posts
On rare occasions I see an nos thermistor for sale. I believe JCC still offers a service to rebuild your old thermistor. I am using a JCC rebuilt unit now and have been for about 7 years and it is still working. Bob's solution sounds like a good one as well.

There are other thermistors out there, used by other auto manufacturers so if one were knowledgeable about such things they may be able to find a replacement using one of the new thermistors available.
+1 for John's, they restored mine with a new thermistor and brass float looks great.
 

·
Registered
Joined
·
643 Posts
It's been 6 years since I replaced my thermistor and it still works fine.

http://www.mercurycougar.net/forums/showthread.php?14674-69-electronic-low-fuel-light&p=135828#post135828.

Since Allied Electronics keeps changing their catalog, most of the links I've left are dead, but the part is still available.

Had it not been for the fact that the sending unit JCC had restored for me (I think he sends them out) was modified (aka ruined) by unnecessary replacement of a connector post terminal with a machine screw (just imagine the gasoline leak), I wouldn't have had to reverse engineer the system myself. This was during a time before Bob's ELFI unit existed.

Although my relay was OK, I had to check the ballast resistor and replace it too.
 

·
Registered
Joined
·
384 Posts
Pull back your trunk floor mat and unplug the two connector plug that is for the fuel sender and low fuel sensor. Use an ohmmeter on a 100 or 200 scale and connect to each pin in the connector going through the trunk floor (to the passenger side) and to a good body ground. You should see 12 ohms and above on either pin. If you do not get a reading (or open) on one pin and your gas guage works ok then the thermistor is bad for the low fuel. If you do get a reading and your gas guage works ok then the problem lies with the relay, resistor, or wiring to the dash.
 

·
Registered
Joined
·
5,633 Posts
Claw it, are you sure about the voltage? I am not looking the schematic, but I was thinking that the fuel gauge feed was after the voltage regulator?
 

·
Registered
Joined
·
384 Posts
The fuel guage feed and sender run off of the voltage regulator. The low fuel light system does not. What I meant previous was to measure the resistance to the tank unit with it is unplugged from the powered systems. If you unplug the connector above the gas tank in the trunk the tank unit becomes isolated from the car and you can make the resistance measurement.
 
1 - 12 of 12 Posts
Top