Gauges not working
Thread Starter
Joined: Jun 2012
Posts: 3
From: New York
Gauges not working
Recently purchased an original 1967 Mustang Coupe, the prior owner had changed the gas tank and now the Fuel Gauge, Temperature Gauge and Oil Pressure Gauge are not working. My husband has the wiring diagram but not sure if they are all tied in together. Has anyone else encountered this problem?
4th Gear Member
Joined: Jun 2006
Posts: 1,483
From: Fontana, California
Welcome to the forum, AleKat,
this is a pretty common problem with this era car. The gauges get a voltage provided by the instrument voltage regulator (IVR) when the ignition key/switch is placed in the Start or Run position. The IVR takes battery voltage and reduces it to 5 Vdc to keep the gauges more reliable (longer life).
So the first thing to check is that the IVR has not failed (it has 5vdc output ). The second thing to check is that the instrument panel is properly grounded and if both are OK then each individual gauge circuit needs to be checked for operation - essentially pull the wire off of each of the sending units and with it "open" the gauge will go full scale one direction; and then ground the wire, the gauge will go full scale the opposite direction.
this is a pretty common problem with this era car. The gauges get a voltage provided by the instrument voltage regulator (IVR) when the ignition key/switch is placed in the Start or Run position. The IVR takes battery voltage and reduces it to 5 Vdc to keep the gauges more reliable (longer life).
So the first thing to check is that the IVR has not failed (it has 5vdc output ). The second thing to check is that the instrument panel is properly grounded and if both are OK then each individual gauge circuit needs to be checked for operation - essentially pull the wire off of each of the sending units and with it "open" the gauge will go full scale one direction; and then ground the wire, the gauge will go full scale the opposite direction.
Joined: May 2012
Posts: 48
From: Colorado
Yeah, I'd suspect the IVR, since it provides the juice to all 3 of those gauges.
However, the original IVR does NOT output 5 volts. It alternates between 0 volts and 12 volts (or system voltage) as the contacts open and close, so that the average is around 5 volts.
Just saying this because if someone is looking at this voltage with a meter, they might be confused when they see the indication flip back and forth.
A solid-state regulator, on the other hand, should provide a relatively fixed voltage.
However, the original IVR does NOT output 5 volts. It alternates between 0 volts and 12 volts (or system voltage) as the contacts open and close, so that the average is around 5 volts.
Just saying this because if someone is looking at this voltage with a meter, they might be confused when they see the indication flip back and forth.
A solid-state regulator, on the other hand, should provide a relatively fixed voltage.
Former Sponsor
Joined: Jul 2012
Posts: 61
From: GA
We have the engine gauge wiring harness for that car which is probable a big part of the solution to why the gauges aren't working. go to our website at mrmustangparts.com and look under wiring or call us at 800-543-9195 from 8-4 monday through friday.
Thread
Thread Starter
Forum
Replies
Last Post