Dumb question of the day

Technical Discussion on Pre-1973 Mustangs

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mungus
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Dumb question of the day

Post by mungus »

So I guess this should be obvious but its slipped my mind somehow...

My 68' 390 has a tachometer (with the oil pressure and alternator idiot lights in the bottom) and a factory type oil pressure gauge. So is there a type of sender (my cars OEM one is gone) that can signal both the the idiot light AND the gauge? I only ask as usually I've found the light switch type oil pressure senders to be small units and the pressure gauge ones to be bigger bulbous shaped things.

Anybody know? I did find a listing in the parts manual for a 390 with a tacho and trip meter; C7AZ-9278-A. But then immediately above it was one specifically for oil pressure gauge cars; B7T-9278-A (but listing no CID's or tacho etc).

So whats the solution? I've never seen a factory tacho car with both types and a Tee fitting. But maybe I wasn't looking hard enough...

Thanks in advance...

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Last edited by mungus on Tue Apr 21, 2020 8:07 am, edited 4 times in total.
Grumpy old git! 68’ S code Fastback
Nuts
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Re: Dumb question of the day

Post by Nuts »

It's my understanding that 67 and 68 cars fitted with tacho did not have an oil pressure gauge. Minor gauges were Fuel, Temp and clock was an option.
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mungus
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Re: Dumb question of the day

Post by mungus »

Well I suppose if that’s the case, and I wanted both the light and the gauge, then I would need both types of sender fitted on a Tee piece and an extra wire to the cluster. (or just decide I don’t need an idiot light altogether). I have had it confirmed now, by the US concourse forum, what many here probably knew anyway, that oil pressure gauge cars didn't come with a functional oil warning light. It was either 1 or the other.

I have emailed a guy in the states who builds new clusters with every option possible to ask him what the story is. Incidentally his website shows clusters with both a tachometer and an oil pressure gauge. But then I guess that may be just what the customer ordered (I would).
Last edited by mungus on Sun Apr 19, 2020 7:13 am, edited 3 times in total.
Grumpy old git! 68’ S code Fastback
Nuts
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Re: Dumb question of the day

Post by Nuts »

fitting another sender for a pressure gauge in a 69 Q code ATM. Not much room around the oil filter adapter in a PS AC car though, will let you know how I get on after I finish the house reno.
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mungus
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Re: Dumb question of the day

Post by mungus »

I think I can make the switch and gauge senders fit with the S code 68 even though its got PS and AC - but only just. There are some good little 1/4 NPT tees available that should make it possible. However as previously mentioned factory cars didn't have both, just 1 or the other. So a choice to be made there. I guess to me it seemed odd as the tacho still has the idiot light in it, and most cars with oil pressure gauges I've driven still had an idiot light. Anyway I guess that's the way Ford did it.

In my imagination If anyone into electronics cold be bothered it's possible to take a feed off the single oil sender wire in the cluster harness, and route it to a small IC switch to drive the idiot light. In which case only the OEM single wire is needed, but that's a whole other drama. I used to have a flatmate in Perth years ago who had the smarts to do that sort of thing...
Last edited by mungus on Sun Apr 19, 2020 7:11 am, edited 4 times in total.
Grumpy old git! 68’ S code Fastback
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