I lost my post because of the VB software. I'll now have to copy the post before posting. It was very extensive, I'll now be brief.

One of the simple solutions would be use a DPDT relay to the oil pressure switch. That gives you to contacts to use. One for the horn and one for the hour meter, Caveat: It would not accumulate engine running without oil pressure.

A sender would be more of a problem.

www.Jacar.com used to have a frequency switch, but they don't have it anymore. They do have a voltage switch.

I had a whole bunch of options, but because of the loss I don;t feel like putting the post together again.

It would be useful to figure out what sensor Chaparral interfaced too. MAF (Mass air flow) might be a choice.

Alternator ripple is another possible way.

 

Well, Chaparral thought they had one more harness left, but they dont. Nor did they have any solutions other than buy a whole new style tach which has the hourmeter in it. So.....looks like i'm undertaking this on my own! Thanks for your help!

 

You could run a 6V relay off of a tap from the alternator and allow 12V to the hourmeter when the alternator is running. Where the stator windings join together (wye or delta) you could use a tap off one of these which will provide 1/2 running voltage. You may have to drop the voltage slightly to get your six volts through the coil on the relay. The load side would just allow 12V to the hourmeter from source.
Just FYI, this is EFI and we do not have points etc to burn out anymore. Ignition systems can be turned on for a long time now with no problems. Depending what year it is, the coils may be individual and triggered by the ECM so you can leave them on all day long with no problems. Older systems use single coils and even those will not have problems being on for extensive periods.
If you can tap off the oil pressure sending unit, this is the best method above all else.
Do not try to tap into the fuel pump circuit. Damage will result to the ECM. It is not made to handle too much current.
Good luck

 

Heres an of the shelf Bosch relay that will do the job.

 

This is how to wire it to run a Hourmeter, Ive tested it & it works.

 

This is how to wire it to run a Hourmeter, Ive tested it & it works.

i Think this is a jackpot. Now I just need to find a cheaper tachometric relay than the $299 for a Lamborghini one.

Thanks Tons!!!

 

Ebay same pin numbers Fuel Pump Relay K.A.E WD express 835 54021 303, $50 US & looks similar.

 

Is it also safe to say that if this relay has they same numbered pins as your schematic then it should also function the same?

http://www.ebay.com/itm/Fuel-Pump-R...id=100033&prg=9336&rk=2&rkt=4&sd=141255414881

 

Looks ok to me.

 

Well, I got the relay today and wired it up and it didnt work. It seems the feed from the tach doesnt pulse. The multimeter reads 5.6-5.8V when the engine is running. So i dont know what the deal is with the tach feed. Any ideas? Im startin to think i may just have to wire it up to the 12v ON position and just remember to tirn the key off when I dont wanna run up hours. Dam$!!!!!

 

Does the hour meter have both leads (pos. & neg.) available?

Use the 5.6vdc to switch power to the meter with a transistor.

 

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Does the hour meter have both leads (pos. & neg.) available?

Use the 5.6vdc to switch power to the meter with a transistor.

Both leads are available, yes. I guess i'm just not knowledgable enough to know how to create/build what you suggest without some specific items to buy/construct.

 

Any small signal or switching npn transistor. Radio Shack ?
http://www.radioshack.com/product/index.jsp?productId=2062609

2N2222 or 2N3904

1000 ohm 1/4 watt resistor connected from 5.6 volt lead to base lead of transistor.

Connect meter+ lead to +12vdc from ignition switch.
Meter - lead to collector lead.
Emitter lead to ground.

If it doesn't work right off. A capacitor might be needed from base to ground. 100uf or so.


https://www.google.com/search?q=2n3...XL8afyQHXwoHIBw&ved=0CDUQsAQ&biw=1024&bih=624

 

Great....thanks for the instructions! I'll mess with this tmrw and see how it al goes!

 

I'm taking a lot for granted on what the signal actually is. And meter impedance.

It should be doable. Nothing to lose trying it.

 

Where does the tach pulse come from? It should come from the Neg terminal on the IGN coil for the relay to work.

 

Another option is these cheep Ebay Tiny tachs for $12. Just wrap the wire a few times around a plug lead, & it gives RPM & total hours run. I use them on my generators.

 

Where does the tach pulse come from? It should come from the Neg terminal on the IGN coil for the relay to work.

The pulse "should" come from the tach. At least, thats what the guy at Chaparral told me. He said the voltage should "pulse" from the tach, but it doesnt seem to. All I see on the multimeter is a 5.6-5.8V readout. I will have to investigate where the actual tach feed comes from on the motor.

 

It may indeed be pulsed. Actually, if it's the signal wire to the tach, it must be pulsed.

No matter, unless it's from an extremely high impedance source, a resistor/ capacitor on the base circuit will average signal just as your meter does. And keep the transistor saturated while motor is running.

If it is a high impedance source it may interfere with tach and not supply enough current to transistor.

That will just require another gain stage or subbing an fet.