Temperature Idiot light, problem

[uk1973]

Hi all, I've been reading this site for many years and was gutted when it disappeared for a while (I guess for a web rewrite) I'm from across the pond, live in London and have an early 73 Convertible, I'm having a problem with the temp idiot light (not gauge), hope you can help...

Can anyone tell me definitively if the ignition key when it is in the ON position whether the Temp light should be illuminated. I'm pretty sure it should as its on the prove out circuit.

What I have is the Oil and Alternator lights on in the 'On' Position. When I twist the key and whilst the starter is throwing the Alternator light flickers strongly as engine starts, when it does and key returns to the normal running position the the light stops flickering and goes out as I would expect with the Oil and Alternator also.

I've replaced many components including rebuilding the dash pod/gauges all bulbs (now leds) correct polarity also new printed circuit board.

I have a big feeling that the problem may be more related to replacing my Ignition switch low down on the steering column. Why? Well I have a early 73, actually made in Dec 72, I replaced with a 73 switch, from rockauto but that P/N corresponds with a 73 part number, but the original P/N corresponds with a 72 I'm trying to work out the difference between 72/3 switches, as there are more owners over there that have these cars I hope you can help with my question.

If your inclined you can read some of my woes on the mustang owners club of Great Britain (69 Coupe) (a very active scene over here in the UK) #17 post will help http://www.mocgb.net/forums/showthread.php?35883-Dead-73-no-ignition-on-turn-of-key-no-indicators-or-radio

Cheers John

 

[uk1973]

Well the weekends upon us, just bumping this in the hope that someone can check on their car does their temperature light come on when switched to the 'On' position.

John

 

[midlife]

No, your temp idiot light will not come on unless the car is overheating with the key on. It is not part of the proof-out circuit. The oil pressure idiot light is part of the proof-out circuit.

You're fine, despite living on the wrong side of the pond and driving on the wrong side of the tarmac.

 

[uk1973]

No, your temp idiot light will not come on unless the car is overheating with the key on. It is not part of the proof-out circuit. The oil pressure idiot light is part of the proof-out circuit.

You're fine, despite living on the wrong side of the pond and driving on the wrong side of the tarmac.

Thanks Midlife,::beer:: thanks for replying, the problem then is how would you know your temp idiot light is working if you switch your ignition on when you first jump in in the morning, you turn your key to 'on' the oil and alternator light comes on I would expect the temp to come on also, to prove that the bulbs are working. You start the car then these lights go out, if you then have an overheat the temp switch on the engine block registers the overheat and the temp switch provides the ground to the temp wire completing the circuit to the idiot bulb which lights telling the idiot driving:whistling: to check the rad water-pump or whatever.

I'll need to pop back up to my garage/lock-up driving on the correct left-hand side of the road on our poorly maintained Scottish/English invented roads The only time veering to the right/wrongside is to miss a pothole which we have many, but I digress...

When I get the time to check I'll put the ignition to the on position and ground the temp wire to check that it comes on, if not I'll try with the engine running, as I definitely know that that circuit is complete as the temp light comes on when throwing the starter.

Many thanks Midlife

 

[Cwithers]

I don't have the idiot lights, but if I was pretty sure the temp light would bulb check with the engine in cranking mode. (starting the engine)

 

[uk1973]

I don't have the idiot lights, but if I was pretty sure the temp light would bulb check with the engine in cranking mode. (starting the engine)

That's what its doing at the moment, flickers when cranking, I just thought it would have been better to come on solid just before you crank the engine then once started go out unless overtemp.

Thinking more once the key goes back to the on/run position there would need to be a way to break the circuit when running so the light is out. I guess it is correct. Still nothing like a good discussion, and by the looks of it idiot lights seem to be more rare than centre gauges, Bahh I must of had a cheapskate buying new in Ohio in 1973 and never ticked the option for centre gauges.

 

[Don C]

It should come on solid when cranking. Does the brake warning light come on when cranking? Both of them have a ground wire running to separate poles on the ignition switch, which provides the ground when in the start position.

 

[midlife]

My bad...the ignition switch for 71-73 does show that the circuit to the temp light is valid when the engine is cranking. Those are the only years of vintage Mustangs that do that.

Just call me an ol' dog, cause I was learned something today!

 

[uk1973]

It should come on solid when cranking. Does the brake warning light come on when cranking? Both of them have a ground wire running to separate poles on the ignition switch, which provides the ground when in the start position.

Don thanks, good you asked about the brake light, as that was going to form part of the next question, well the answer is no it does not come on when cranking, this could still be a switch or wiring problem to the proportioning valve, as the wire plug was disconnected, I did reconnect but the light didn't come on for the brakes on cranking, I know all dash lights are good they are all new LEDs on a new printed circuit board, it was not as important as the temp light because I know many disconnect the brake switch if the proportioning valve has moved and not been recentralised. I did become curious about it when I left the lock-up, as apparently you can have an e-brake switch, I checked and could not find a switch on the e-brake.

My brain is frazzled looking at wiring diagrams, what I've done below is copy the 73 switch wiring and 72 switch wiring from the wiring pdf's and merged into a single picture. Can anyone tell if those two switches are the same for temp brake prove out? as said, I have an early 73 and the pn on the original switch I replaced has a 72 p/n and RockAuto.com show two different p/n for 72 and 73 mustangs, I bought the 73 switch p/n, maybe I need the 72 switch...

John

 

[uk1973]

It should come on solid when cranking. Does the brake warning light come on when cranking? Both of them have a ground wire running to separate poles on the ignition switch, which provides the ground when in the start position.

Don thanks, good you asked about the brake light, as that was going to form part of the next question, well the answer is no it does not come on when cranking, this could still be a switch or wiring problem to the proportioning valve, as the wire plug was disconnected, I did reconnect but the light didn't come on for the brakes on cranking, I know all dash lights are good they are all new LEDs on a new printed circuit board, it was not as important as the temp light because I know many disconnect the brake switch if the proportioning valve has moved and not been recentralised. I did become curious about it when I left the lock-up, as apparently you can have an e-brake switch, I checked and could not find a switch on the e-brake.

My brain is frazzled looking at wiring diagrams, what I've done below is copy the 73 switch wiring and 72 switch wiring from the wiring pdf's and merged into a single picture. Can anyone tell if those two switches are the same for temp brake prove out? as said, I have an early 73 and the pn on the original switch I replaced has a 72 p/n and RockAuto.com show two different p/n for 72 and 73 mustangs, I bought the 73 switch p/n, maybe I need the 72 switch...

John

Had 30 mins at lock-up on Monday, turned ignition key and the oil /alt come on when at the 'on' position, I kept slowly turning the key until it was under spring-back pressure as key goes into the 'start run' area to engage starter, the temp light lit brightly and stayed lit then stayed lit when the starter was throwing, this is good and as you guys have said it's how it should work to prove Temp idiot light would come on I grounded the Temp wire off the engine block and the Temp light came on, proving it works as you say in the 'on' position. case closed!!

The Brake idiot light never lit up and I made a loop of wire for the brake pigtail twin connector, these are the two pink/white wires but light never came on, had to call quits for the rest of the day.

Looking at the wiring for the brake connection at the dual brake warning switch that loop I made may also needed to be grounded I didn't try that and will the next time I pop up. The only other problem that it could be the Led is in the incorrect way as I've had the dash in and out many times and the Brake idiot light was least of my problems. I'm getting there. Also looks like 72/73 switches are the same just different p/n.

John

 

[73Vert302]

Now I have a problem...its with the Oil Pressure idiot light. I just installed Rocketmans tach/idiot light conversion (btw...it works great!). BUT, I believe I messed up the printed circuit when I was trying to plug the harness back in. Can it be repaired? I think the contact end is still attached, but kinda crumbled up. Plus, is yours as tight a fit as mine? I am hooking it up reaching from the top with the dash and vent tube removed. Is this how you hook it up? Its so tight I am doing it blind cause I cant see it from the front to carefully reinsert it. HELP!!!

 

[Don C]

In response to your question about the switch p/n, it's fairly common for parts from one year to carry over to the next year(s). The switch positions in the diagrams for the '72 & '73 switches are the same. NAPA shows the same switch for '71, '72, & '73, so the one you got from Rock Auto should be OK.

 

[uk1973]

Now I have a problem...its with the Oil Pressure idiot light. I just installed Rocketmans tach/idiot light conversion (btw...it works great!). BUT, I believe I messed up the printed circuit when I was trying to plug the harness back in. Can it be repaired? I think the contact end is still attached, but kinda crumbled up. Plus, is yours as tight a fit as mine? I am hooking it up reaching from the top with the dash and vent tube removed. Is this how you hook it up? Its so tight I am doing it blind cause I cant see it from the front to carefully reinsert it. HELP!!!

Hi sorry to hear your having woes too, I found the only easy way to reconnect the cluster to the pigtail was to remove the dash pad, its only approx 10 screws to take that off, you can then get your hand in from top and sort of see what you are doing, once its at the right angle and right way around it clips in fairly easily and is snug, you will know when its home.

But! you have another problem with the pcb tracks folding or coming away from the plastic circuit film, this was what had orginaly happened to me, I removed the PCB and glued the tracks back down with industrial superglue, they did stick but left a clear film of glue over the copper tracks, this caused loads of problems with poor connections, I cleaned all the copper tracks with emery paper, including all the bulb holder connections. This ultimately failed in my instance as I was taking cluster in and out the tracks broke away became brittle and the plastic started to delaminate from the copper, I was fighting a losing battle. I have since found out that some recommend epoxy glue.

I looked into getting a new PCB, many stock them, I spent many a night trying to find the best deal, very important to get costs down when in the UK, in the end Johns Mustang of Dallas were doing a deal for only $49 which I bought and the quality is excellent. I've just checked Johns mustang of Dallas but looks like out of stock and price now $80, I did have another dealer with the lower price offer and I've gone back over my browsing history, and good news they can still be had for $49 from http://www.macsautoparts.com/ford_mustang/ford-mustang-printed-circuit-board-with-tachometer-71-73.html for that money I'd replace and take consolation that this will get rid of most of your dash gremlins.

John

In response to your question about the switch p/n, it's fairly common for parts from one year to carry over to the next year(s). The switch positions in the diagrams for the '72 & '73 switches are the same. NAPA shows the same switch for '71, '72, & '73, so the one you got from Rock Auto should be OK.

Thanks for confirming Don, I'm slowly getting there

 

[73Vert302]

Thanks!

 

[uk1973]

Just realised that I may have posted this thread in the wrong place, just noticed the 'Electronics, Security, Audio Systems' sub-forum, maybe the Mods can move it if they so wish.

Hey ::new::