Early 70's Ignition Coil Capacitor?

[Roger S.]

In working to eliminate my radio noise I have found a capacitor connected to the positive side of the ignition coil and it is attached to the coil bracket. The AIM, NCRS judging books and other Corvette books I have do not show or mention this capacitor. Does anyones' early 70's have this capacitor? There is a capacity inside the distributor connected to the points and a capacitor on the HVAC blower motor.

Roger

[Jeffrey S.]

Re: Early 70's Ignition Coil Capacitor?

Roger:
I'm not sure if the '70 and up is the same as my '69 but that capacitor is connected at the positive side of the coil and the coil bracket and is pictured in the U69 (radio option) pages of the AIM. The '69 is page A4. Your pages may be numbered differently but check that section.
Jeff

[Kenneth T.]

Re: Early 70's Ignition Coil Capacitor?

In working to eliminate my radio noise I have found a capacitor connected to the positive side of the ignition coil and it is attached to the coil bracket. The AIM, NCRS judging books and other Corvette books I have do not show or mention this capacitor. Does anyones' early 70's have this capacitor? There is a capacity inside the distributor connected to the points and a capacitor on the HVAC blower motor.

Roger

Roger,
My '71 has the capacitor on the coil pn 1947452 in the AIM UPC U69, sheet A4.

[Tom L.]

Re: Early 70's Ignition Coil Capacitor?

While changing the points and condenser in my '72 I saw that the capacitor wire on the coil was broken. I removed it and finished with my points change. After driving the car I noticed that the radio noise that I had was mostly gone. Don't know if you canged the points lately but it may be worth a try.

Merry christmas!!

[Jack H.]

Re: Early 70's Ignition Coil Capacitor?

As others mentioned, the cap external to the ignition coil is called out as part of the U69 radio option. It's a Delco Remy 1947452 and it's job is reduce RF interference at the noise source (spark plugs switching ON/OFF) by presenting a low impedance path to ground for the high frequency AC transients created by switching DC...

There are several 'hush up' capacitors called out in the radio option and each addresses a separate noise source. ALL need to be present/intact along with the RF shields called out in the U69 option section to create a clean quiet working environment for the radio.

Electrical noise can propagate by conduction and radiation which is why Corvettes always had the radio antenna located at the rear of the car (as far away from the engine compartment as possible). The solution(s) were to hush up noise at its source(s) which include the ignition, the battery charging system, the heater blower fan motor, headlight/dimmer switch, and various dash board components...

[Roger S.]

Re: Early 70's Ignition Coil Capacitor?

I found it in the 73 AIM. It is in section B01-B12 sheet 32. The sheet is labeled Capacitors. Other capacitors are shown on sheet 31. The p/n listed is 1852715.

How do you check a capacitor to see if it working?

Roger

[Mike E.]

Re: Early 70's Ignition Coil Capacitor?

Check the archives--there's been a significant discussion on that in the last month. Jack Humphrey gave excellent information.

[Roger S.]

Re: Early 70's Ignition Coil Capacitor?

A capacitor is not a capacitor! I started checking for the little critters in the car and several look alike but in one of the older posts it showed each capacitor had a different mFD rating. Also, the p/n changes from the 71 to my 73. Is the rating needed for each application listed anywhere? Most of the vendor catalogs I have don't list many of the capacitors except ZIP's.

Roger