Warren Seale

Does anyone have a photo showing the correct way to route the external voltage regulator capacitor wire? This is for a 72 Cutlass with rear the rear window defogger grid and no A/C.

67OAI

Do you have the mechanical voltage regulator or an electronic (transistorized) replacement?

67OAI

Portion of the wiring diagram shown as a "sticky" in the "Electrical" forum; if you have the transistorized VR, no capacitor is needed.

ART T

Will the capacitor harm the ER?

Tri-Carb

The capacitor attached to the case on the external, mechanical voltage regulator performs two functions. It suppresses EMP when the regulator contacts open so you do not hear it in the audio circuit of your radio. ( EEs would say that say that it adds VARs to a transient circuit whose Thevenin equivalent circuit appears biased towards the inductive side.) And it suppresses the electric arc created when the contacts open and thereby enhances their longevity.

When you go the solid state style regulators, the mechanical switching is eliminated.

ART T

Thank you.

Vintage Chief

Do you have the PIM? I have the '72 PIM which demonstrates a wiring diagram including the various relays, window defogger, VR & capacitor. You want that or are you good?

Vintage Chief

Here, I'll toss these up for you. I think you might one or two helpful. NOTE: I didn't review each for detail but I noted there may be a delta w/ AC vs. w/o AC.

ART T

Thanks, I'm good. I changed to an electronic one when I read that it could spike and take out the module in the HEI.

Vintage Chief

The OP asked for photos perhaps they’ll assist.

Loaded68W34

The bigger question is how was the grid defroster wired when ordered on a 442? I have looked in the PIM and have not found anything. The purpose of the wire running off of the capacitor lead on the voltage regulator is to only allow the grid to be on while the engine is running (regulator & alternator are charging), but I cannot find any reference to how the system was wired on a 442 which would have an open face internally regulated alternator and no voltage regulator on the firewall. Ideas?

Fun71

I think that is a non-issue. My car has worked just fine with a GM HEI along with a mechanical voltage regulator since 1982 and it’s still on the same ignition module. Now the voltage regulator failed twice during that time, and I repaired it and put it back into service.
If a totally failed voltage regulator doesn’t take out the ignition module, I doubt a transient voltage spike would.

OldOldsLover

1972 Cutlass Supreme without rear defroster and with air conditioning. Hope it helps.

Warren Seale

Can I assume that the photos above show the original factory routing? So, the wire feeding the capacitor runs behind the voltage regulator?

The illustrations show the wire just flying in the air. This is probably not correct but necessary to show how the wires are interconnected.

Warren Seale

Mechanical.

OldOldsLover

I believe this is the way it came from the factory.

Loaded68W34

No,
The photos show a capacitor and regulator in a system without a rear defroster but with A/C (exactly the opposite of what you are looking for). The defroster wiring shown in the diagrams is correct (although the wire may not be positioned that high). The capacitor wire on the rear defroster cars ensures that the grid will only be on while the car is running (while the system is charging). So, even if the ignition is on, if the car is not running the grid will not turn on. The main power feeding the relay comes off of the horn relay junction as seen in the diagram, but the wire providing power to the switch in the dash that turns the relay on comes from the terminal on the voltage regulator that would normally just have a capacitor plugged into it. The photos show the regular system where only a capacitor is plugged onto the voltage regulator not the defroster harness.