Put in $30 worth of premium and gauge went to Empty

7173Mustangs.com

Help Support 7173Mustangs.com:

Joined
Jun 14, 2019
Messages
460
Reaction score
84
Location
Coachella Valley (Palm Springs)
My Car
1973 Convertible, 351 4v CJ, C6, Mach 1 Decor options, power: steering, brakes and windows, a/c, Rally Pac gauges, Deluxe interior.
[url=https://ibb.co/ZVjjKXW][img]https://i.ibb.co/zrMMbxG/s-l1600-2.jpg[/img][/url]
Car went to the shop for tuning, replace gas tank & sender and other work.  They gave me back my car with about 1/4 of a tank showing on the gauge. Before the new sender, it only ever registered Empty.  A few short drives around the 'hood over a few weeks and the tank was again approaching E so drove down and put $30 worth in (at $4.59/gal, was about 5-6 gallons).  After the shop visit, all gauges (including fuel!) were working great.

After getting gas and starting the car up, the gauges were seemingly DOA.  Fuel gauge:  less than empty.  Oil: no pressure.  Ammeter: no movement.  Temp:  below "C" (and I'd driven around a bit before getting gas so car was easily warm).  Drove home -- no change.  No pressure, no juice, no temp and looked like no gas.  As I pulled into the driveway, I was already composing this post.

Turned the car off and got out, then something told me to start it again so I did.  All gauges registered normally!  1/2 tank gas, medium oil, slight positive juice, firmly middle of the gauge temperature. 

What's up with this?

 
Joined
Jan 1, 2012
Messages
8,233
Reaction score
969
Location
Springfield, OR
My Car
1971 Mustang Sportroof M code
The common factor for all gauges, other than the ammeter, is the instrument voltage regulator. Old ammeters are notoriously lacking in movement.

Your ignition switch may not have been making contact on the accessory feed contacts or you may have a loose wire, either voltage feed or ground to the IVR. When it happens again, try jiggling the ignition switch.

 
Joined
Jun 14, 2019
Messages
460
Reaction score
84
Location
Coachella Valley (Palm Springs)
My Car
1973 Convertible, 351 4v CJ, C6, Mach 1 Decor options, power: steering, brakes and windows, a/c, Rally Pac gauges, Deluxe interior.
[url=https://ibb.co/ZVjjKXW][img]https://i.ibb.co/zrMMbxG/s-l1600-2.jpg[/img][/url]
44 minutes ago, Don C said:When it happens again, try jiggling the ignition switch.
Thanks - will do!

 
Joined
Jun 14, 2019
Messages
460
Reaction score
84
Location
Coachella Valley (Palm Springs)
My Car
1973 Convertible, 351 4v CJ, C6, Mach 1 Decor options, power: steering, brakes and windows, a/c, Rally Pac gauges, Deluxe interior.
[url=https://ibb.co/ZVjjKXW][img]https://i.ibb.co/zrMMbxG/s-l1600-2.jpg[/img][/url]
Don C hit a bingo on this one.  For engine, seems the key can be anywhere between OFF and START (3/8"? of play), but for gauges, the correct alignment is right up next to where the resistance begins before START.

 
Joined
Aug 14, 2014
Messages
3,678
Reaction score
593
Location
Madison, WI
My Car
1971 M-Code Mach 1 w/408C stroker
The common factor for all gauges, other than the ammeter, is the instrument voltage regulator. Old ammeters are notoriously lacking in movement.

Your ignition switch may not have been making contact on the accessory feed contacts or you may have a loose wire, either voltage feed or ground to the IVR. When it happens again, try jiggling the ignition switch.
+1

It has happened to me a few times. I just need to rotate the key back a little for the needles to move again.

 
Joined
Jun 14, 2019
Messages
460
Reaction score
84
Location
Coachella Valley (Palm Springs)
My Car
1973 Convertible, 351 4v CJ, C6, Mach 1 Decor options, power: steering, brakes and windows, a/c, Rally Pac gauges, Deluxe interior.
[url=https://ibb.co/ZVjjKXW][img]https://i.ibb.co/zrMMbxG/s-l1600-2.jpg[/img][/url]
Sounds like time for a new ignition switch!!
Is it the ignition lock cylinder or the ignition switch that needs to be replaced?  Seems if jiggling the key into the just right position solves the problem, then it would be the lock cylinder, not the switch, but the lock cylinder has no electrics just a rod that goes to the switch.

Screen Shot 2021-11-11 at 11.05.38 AM.jpg

 
Last edited by a moderator:
Joined
Jan 1, 2012
Messages
8,233
Reaction score
969
Location
Springfield, OR
My Car
1971 Mustang Sportroof M code
Jiggling the key moves the rod that moves the switch. Either your switch needs adjusting or you need a new one. The grease in the switches dries out, which makes it difficult for the slide in the switch to move, and also gums up the contacts, so jiggling it can make it move that last fraction of an inch to make contact.

 
Joined
Jun 14, 2019
Messages
460
Reaction score
84
Location
Coachella Valley (Palm Springs)
My Car
1973 Convertible, 351 4v CJ, C6, Mach 1 Decor options, power: steering, brakes and windows, a/c, Rally Pac gauges, Deluxe interior.
[url=https://ibb.co/ZVjjKXW][img]https://i.ibb.co/zrMMbxG/s-l1600-2.jpg[/img][/url]
Alrighty then, I replaced the switch.  Gauges still don't work.  With a new switch in place, the key movement is pretty firm, that is, no jiggle.  So there's no toying with the key to make gauges wake up.  Car starts, operates as expected through all the key positions.

I did also replace all the dash lights and the IVR; didn't like the level of brightness so replaced them again (will see tonight if the 5x brighter does the trick), and then I replaced the ignition switch.  The lock cylinder, for now, is still original.

Did I miss something with the IVR?  It looks pretty simple and there's only one place for it.   It just screws in and there's nothing else to hook up.

Barring that, other suggestions?

 
Joined
Jan 1, 2012
Messages
8,233
Reaction score
969
Location
Springfield, OR
My Car
1971 Mustang Sportroof M code
Do your accessories, like heater, radio, and turn signals work? They receive power from the same circuit that feeds the instrument voltage regulator. As has been stated many times on this forum, new does not mean good, lots of parts are bad out of the box. Were you careful when you pulled the old IVR off the printed circuit, doesn't take much to break the 50 year old printed circuit. Did the new IVR make good connections to the printed circuit?

 
Joined
Jun 14, 2019
Messages
460
Reaction score
84
Location
Coachella Valley (Palm Springs)
My Car
1973 Convertible, 351 4v CJ, C6, Mach 1 Decor options, power: steering, brakes and windows, a/c, Rally Pac gauges, Deluxe interior.
[url=https://ibb.co/ZVjjKXW][img]https://i.ibb.co/zrMMbxG/s-l1600-2.jpg[/img][/url]
Yes, heater, radio & blinkers all work fine.

I was planning to change to LEDs so I started with replacing the printed circuit, followed by new IVR and then bulbs.

How would I test if the IVR was making good connections? Seems garages not working would say “no”.  It screws into place on the circuit and also connects to a 9-volt type connection. Everything is snug.

I still have the old IVR which was working so I could put it back in for testing, and I have an extra new IVR because I over-ordered.

Update: Since the question was IVRs, while I awaited an answer, I pulled the instrument cluster, removed and examined the IVR (no issues) then reinstalled it.  Really, I did nothing but remove it, look it over and put it back (did not remove from the 9-v connection, just the screw holding it to the cluster).  And now everything works fine!

Bravo, Don -- many thanks.

 
Last edited by a moderator:

midlife

Shorts checker
Joined
Jan 24, 2012
Messages
4,160
Reaction score
584
Location
Tucson, AZ
My Car
No Mustangs at the moment.
Do your accessories, like heater, radio, and turn signals work? They receive power from the same circuit that feeds the instrument voltage regulator. As has been stated many times on this forum, new does not mean good, lots of parts are bad out of the box. Were you careful when you pulled the old IVR off the printed circuit, doesn't take much to break the 50 year old printed circuit. Did the new IVR make good connections to the printed circuit?
The IVR power comes directly from the ignition ACC via a resistor wire and is NOT part of the same circuit (fused) as the radio, backup lights, and washer motor.  Turn signals are also ACC powered, but not part of the resistor wire system.  The resistor wire starts at the main power for the wiper switch, however. 

 
Joined
Jan 1, 2012
Messages
8,233
Reaction score
969
Location
Springfield, OR
My Car
1971 Mustang Sportroof M code
The point is, they all come from the same connector on the ignition switch, and if the accessories work the IVR circuit will also be getting voltage. So, the problem is either in the circuit (connectors, resistor wire, printed circuit) leading to the IVR, or in the IVR. 

It also means the ignition switch is adjusted correctly.

 
Last edited by a moderator:
Joined
Jun 14, 2019
Messages
460
Reaction score
84
Location
Coachella Valley (Palm Springs)
My Car
1973 Convertible, 351 4v CJ, C6, Mach 1 Decor options, power: steering, brakes and windows, a/c, Rally Pac gauges, Deluxe interior.
[url=https://ibb.co/ZVjjKXW][img]https://i.ibb.co/zrMMbxG/s-l1600-2.jpg[/img][/url]
It also means the ignition switch is adjusted correctly.
And now there is none of the jiggle in the ignition lock cylinder, i.e., "where the key goes" - hooray! 

Will still eventually swap it out since doors don't unlock with the ignition key.  I've always been reluctant to lock a convertible because leaving it unlocked hopefully prevents someone from tearing through the top to get in the car.

 

midlife

Shorts checker
Joined
Jan 24, 2012
Messages
4,160
Reaction score
584
Location
Tucson, AZ
My Car
No Mustangs at the moment.
Was this car originally from Las Vegas?  I ask since putting in $30 and getting nothing in return is common in that neck of the woods...

 
Top