I need to replace my original 1800 armored coil with a new coil. I understand that the original Bosch coil was engineered with an internal resistor. Is a new internal resistor coil the same or should I use and external resisted coil and resistor? If so, how would that be wired?

Thanks,
Steve
'66S

Do you still have the original ignition switch that is attached to the coil via the armored cable?
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Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

Yes. The key and tumbler are different but the switch is the same with the armored cable attached, cut off where the original coil was.

Here's what we prefer to do when the coil is bad, but the ignition switch is still functioning.

We remove the coil housing from the armored cable by twisting the coil off the end of the armored cable by clamping the armored cable close to the coil in a bench vise and unscrewing the coil from the armored cable and cutting the wire inside the armored cable as close to the coil as possible.

Then using the same technique, we remove the armored cable from the switch which will leave you with a long easily routable wire to connect to the new coil. You'll still have to extend the wire to reach the positive pole on the new coil.

We then cut the top and bottom from the old coil housing and gut it so you can use the remaining housing to hold a new coil. When cutting and gutting the coil housing, I strongly suggest you wear a particle mask and eye protection. We're not sure what's inside, possibly some PCBs so better safe than sorry.

All the new coils we've used are smaller in outer diameter so to keep the coil from moving around inside the old coil housing, we glue 2 strips of rubber to the outside of the new coil to make a tight slip fit. We like to leave a gap in the ends of the rubber strips and we stagger the gaps to allow for some air circulation.
--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

Thanks to all for the help.

Steve
'66S

Steve;

If the Ign Sw and Armored Cable have been previously cut in order to get access to the Ign Power node to the Ign Coil +, you can simply wire in the correct Ign Coil as Derek has described, based on the info here: https://www.sw-em.com/Volvo%20Ignition%20from%20Scratch.htm#Vintage%20Volvo%20Ignition%20system%20and%20the%20Armored%20Cable

Cheers

If you really need to replace your armoured coil, they rarely fail, you just need a 3 ohm replacement. The Bosch Blue usually gets a recommendation but make sure you get a proper one. Some of the repros are sub standard.