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lm coil for xr700 ,ignition
Posted by: hjackson3149 ()
Date: October 06, 2019 09:20AM

good afternoon all

I believe my coil is getting hot and causing problems
what is the best coil available from local autozone etc.
using xr700 ignition

Hank Jackson
South Florida
69 Monza PG
everybody has to believe in something and
I believe I will have another.
one for the Road!

The Three Stages of Christine

;;

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Re: lm coil for xr700 ,ignition
Posted by: MattNall ()
Date: October 06, 2019 11:48AM

Check the primary winding resistance and buy on with a slighlty higher reading.

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

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Re: lm coil for xr700 ,ignition
Posted by: TerribleTed ()
Date: October 06, 2019 12:01PM

Stock spec coil is fine with the XR700

---------------------------------------------------------------------------------------------------------

Avid Corvair hobbiest since 1984.
I have personally performed ground up restoration on over 20 Corvairs.
I currently work full time at restoring and repairing Corvairs.
Located in the Atlanta Georgia area.
[www.facebook.com]

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Re: lm coil for xr700 ,ignition
Posted by: RKF ()
Date: October 06, 2019 12:20PM

Has the resistor wire leading to the coil been replaced with regular wire? If so, you need a coil with 3.0 ohms on the primary winding. If you are using resistor wire or an external resistor in series with the coil, you will need a coil with a primary resistance of 1.8 ohms.

In other words, if you have 12 volts at the coil with the key on, use a 3.0 ohm coil. If you have 7 - 10 volts at the coil, use a 1.8 ohm coil.

Hope that helps.

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Re: lm coil for xr700 ,ignition
Posted by: TerribleTed ()
Date: October 06, 2019 12:24PM

RKF Wrote:
-------------------------------------------------------
> Has the resistor wire leading to the coil been replaced with regular wire? If so, you need a coil with 3.0 ohms on the primary winding. If you are using resistor wire or an external resistor in series with the coil, you will need a coil with a primary resistance of 1.8 ohms.
>
> In other words, if you have 12 volts at the coil with the key on, use a 3.0 ohm coil. If you have 7 - 10 volts at the coil, use a 1.8 ohm coil.
>
> Hope that helps.


If the resistor wire is not in place do not use the XR700 until it is replaced as that ignition is not made for constant 12V.

---------------------------------------------------------------------------------------------------------

Avid Corvair hobbiest since 1984.
I have personally performed ground up restoration on over 20 Corvairs.
I currently work full time at restoring and repairing Corvairs.
Located in the Atlanta Georgia area.
[www.facebook.com]

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Re: lm coil for xr700 ,ignition
Posted by: 66vairman ()
Date: October 06, 2019 02:42PM

In the first paragraph of the XR700 instructions -- "The XR700 requires ballast resistance to limit coil current." In the ballast resistance section it says the XR700 requires 3-4 ohms of resistance, either a coil plus external resistor, or a coil with internal resistor.

Corvair ballast wire should be about 1.8 ohms and the coil should be about 1.3 ohms for a total of about 3.1 ohms.

I've run into so many missing/broken/by-passed ballast wires, WRONG coils, or defective "high output" coils that I only use a quality brand replacement coil with the stock ballast wire.

A 1965 Chevy Impala small V8 replacement coil is a close to a stock Corvair coil as you'll find now. If the ballast wire is broken or missing you can buy a new harness or install a ceramic ballast - NOTE there are many different ohmic value ceramic holder resistors so of needed use the correct value resistor - 1.8 ohms.

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Re: lm coil for xr700 ,ignition
Posted by: hjackson3149 ()
Date: October 11, 2019 08:21AM

good morning all

to clarify
new wiring harness with resister wire intact
not sure where coil was bought.
coil seems to be getting real hot and starts to stumble and stall

dumb question how do you check the primary coil resistance
on a new coil or any coil ?

Hank Jackson
South Florida
69 Monza PG
everybody has to believe in something and
I believe I will have another.
one for the Road!

The Three Stages of Christine

;;

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Re: lm coil for xr700 ,ignition
Posted by: larry202br ()
Date: October 11, 2019 08:33AM

Coils normally do get warm, so that may be normal. But they can overheat.

To measure coil resistance, you would use a meter that reads resistance. Those meters are called ohmmeters. you may have a multifunction meter called a DMM, or digital Multimeter, which includes an ohmmeter.

Select the ohm function, and use the lowest ohm scale. Short the test together, and record the reading, for example, 1.2 ohms. then touch the leads to the coil primary, and record the reading. Subtract the reading you got when shorting the leads together from that reading, and that is your coil primary resistance.

1961 rampside with a 65 / 67 110 engine, car four speed.
1965 convertible
1966 Custom two door/four door 180 Turbo.

KC0SKX
Olathe, ks
HACOA

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Re: lm coil for xr700 ,ignition
Posted by: 66vairman ()
Date: October 11, 2019 09:45AM

The XR700 instructions do mention that IF the xr700 box gets hot then verify coil and ballast resistance.

If only the coil gets hot then the coil may be defective. Since you mention "coil seems to be getting real hot and starts to stumble and stall" the coil should be verified. If it's resistance is O.K. then a simple check to find a loaner replacement to use.

If resistances looks good, then post here. There are other things to check, but they are very uncommon problems.

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Re: lm coil for xr700 ,ignition
Posted by: hjackson3149 ()
Date: October 11, 2019 10:25AM

good afternoon all

ohm meter shorted together = .1 ohm
across pos and neg on coil = 1.5
appears to be generic coil

is this sufficient.
or should i just replace it?

Hank Jackson
South Florida
69 Monza PG
everybody has to believe in something and
I believe I will have another.
one for the Road!

The Three Stages of Christine

;;

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Re: lm coil for xr700 ,ignition
Posted by: MattNall ()
Date: October 11, 2019 11:18AM

That's good readings... shouldn't overheat.... find / borrow a coil with 2-3 ohms and try it..v for a test..

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

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Re: lm coil for xr700 ,ignition
Posted by: larry202br ()
Date: October 11, 2019 11:25AM

Since you have ballast resistance wire, it should be about 1.8 ohms, to equal the (approx.) 3 ohms you need. Is your coil still mounted on the engine? many move the coil to the rear vertical brace to keep it cooler. Just because the resistance checks good, doesn't necessarily mean the coil isn't failing when hot.

1961 rampside with a 65 / 67 110 engine, car four speed.
1965 convertible
1966 Custom two door/four door 180 Turbo.

KC0SKX
Olathe, ks
HACOA

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Re: lm coil for xr700 ,ignition
Posted by: oldqmguy ()
Date: October 11, 2019 12:59PM

hjackson3149 Wrote:
-------------------------------------------------------
> good afternoon all
>
> ohm meter shorted together = .1 ohm
> across pos and neg on coil = 1.5
> appears to be generic coil
>
> is this sufficient.
> or should i just replace it?

This means that the coil primary resistance is 0.5 ohms!! hot smiley

Definitely NOT the right coil!

If the meter reads 1 ohm with the leads shorted together, a correct reading would be 2.8 ohms (meter's dead short reading + primary coil resistance)!!!!

Looks like a bad coil to me! eye rolling smiley

Dale ????

Dale E. Smiley CPBE
Life Member The Society of Broadcast Engineers
RETIRED Broadcast Engineer
CERTIFIED CORVAIR NUT
CORSA/Circle City Corvairs/Corvair Performance Group
Avon, Indiana
WB9SFF
1967 4-Door Monza PG!

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Re: lm coil for xr700 ,ignition
Posted by: 66vairman ()
Date: October 11, 2019 05:19PM

oldqmguy Wrote:
-------------------------------------------------------
> hjackson3149 Wrote:
> -------------------------------------------------------
> > good afternoon all
> >
> > ohm meter shorted together = .1 ohm
> > across pos and neg on coil = 1.5
> > appears to be generic coil
> >
> > is this sufficient.
> > or should i just replace it?
>
> This means that the coil primary resistance is 0.5 ohms!! hot smiley
>
> Definitely NOT the right coil!
>
> If the meter reads 1 ohm with the leads shorted together, a correct reading would be 2.8 ohms (meter's dead short reading + primary coil resistance)!!!!
>
> Looks like a bad coil to me! eye rolling smiley
>
> Dale ????

Ummmm - Hjackson said -- 1.5 ohm minus 0.1 ohm (dmm leads) and that equals 1.4 ohms, NOT 0.5 ohms. That ol decimal point will get ya.

Yeah 1.4 primary resistance is fine. Now you need to verify ballast wire @ 1.8 ohms. If that is good install a good loaner coil. So 1.4 ohm plus ballast 1.8 ohms is a total of 3.2 ohms. That's fine. You want total resistance of 3 - 4 ohms for reliable operation.

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Re: lm coil for xr700 ,ignition
Posted by: oldqmguy ()
Date: October 11, 2019 10:38PM

OOPS!

Seeing that PERIOD on a 7" Kindle isn't that easy! sad smiley

"Assuming" that the dead-short resistance is POINT 1 (0.1) Ohm, then the coil should be OK at 1.4 ohms!

I would still substitute it with another one just to be sure.

Dale cool smiley

Dale E. Smiley CPBE
Life Member The Society of Broadcast Engineers
RETIRED Broadcast Engineer
CERTIFIED CORVAIR NUT
CORSA/Circle City Corvairs/Corvair Performance Group
Avon, Indiana
WB9SFF
1967 4-Door Monza PG!

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Re: lm coil for xr700 ,ignition
Posted by: joelsplace ()
Date: October 15, 2019 01:48PM

So the XR700 doesn't care what the voltage to it is as long as coil current is correct? That's what the above instructions say. Seems odd.

Joel
Northlake, TX
5 Ultravans, Lost count at 100 Corvairs...

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Re: lm coil for xr700 ,ignition
Posted by: larry202br ()
Date: October 16, 2019 01:00PM

No mention of voltage to the XR700, only coil voltage. The reduced current to the coil, due to internal resistance, and the ballast wire, keeps the coil cool (cooler) while running

1961 rampside with a 65 / 67 110 engine, car four speed.
1965 convertible
1966 Custom two door/four door 180 Turbo.

KC0SKX
Olathe, ks
HACOA

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