Bad voltage regulator symptoms?

ernestedward · 12-29-2004, 10:52 AM

What are some symptoms of a failed or failing voltage regulator? Does it slowly go bad or does it just stop working? Will the car still run with it going bad?

I was thinking maybe my recent electrical issues may be related. For my heater blower, I'm not getting nearly enough voltage (3v) and at my radio i'm getting 22V. Radio won't power up, of course. I'm certain that the radio should get 12V, or right around that, because I had to fix the wiring behind it myself a few months ago.

Any ideas?

SoCal Driver · SoCal Driver's Garage

Kee-riest! 22 volts??? You should be able to arc weld!

Get a digital voltage meter that does tenths of a volt and check the voltage at the battery terminals. Should be over 13 volts when running at 2000 rpm or better.

If not then start checking all the connections. Grounds between the engine and chassis at the back of the block are usually the main culprits. The large cable going to the starter is the path the charging voltage comes back into the battery and then to the cars systems via the three large red wires. Clean the battery terminals.

If the voltage at the battery is less than 13 and all of the major connections have been cleaned then you just may need new brushes for your alternator. About $25 at a decent parts store.

toolboy62 · 12-29-2004, 08:39 PM

If you're really reading 22 volts check it at the battery and if it is still 22V shut it down and leave it until you get it fixed! There's a lot of electronics to fry in a Porsche... I really can't think of any way to get a potential over 14V in a car, the chassis usually grounds itself to earth fairly well through the tires.

nate

SoCal Driver · SoCal Driver's Garage

The alternator does about 16 volts max when shorted past the regulator. There is a round hole in the back casting to do this as a test.

ernestedward · 12-30-2004, 08:17 AM

Boy, is my face (partially) red....Problem #1 is a bad voltmeter. Replaced the batteries in it and now I'm getting a much more reasonable 12.3V at the battery, and the same for the radio. So, looks like the head unit is bad. Guess I'll have to call crutchfield. SoCal - I think you're right about the brushes, it's probably just not charging as well as it should.

In regards to your second post, I'm assuming it's no longer necessary to check the regulator. It's pretty damn cold on the concrete floor.

So I'm back to square one (and a half) with my blower motor. Just to clarify, a BAD resistor pack will cause the fan to stop working ONLY in the first and second positions? As I understand it, it should work in the third (highest) position even if the pack is corroded or bad?

SoCal Driver · SoCal Driver's Garage

Should have over 13 volts at the battery with the engine at medium rpm's. You are getting 12.3? Regulator/brushes IF all of the grounds and main feed wire contacts have been cleaned.

Replace the switch for the blower fan. These are plastic and melt when the blower motor starts dragging and drawing more amps than the switch is designed to handle. Check the resistor bridge under the outside plastic cover.

Also there is an interlock relay with the A/C that can disable the fresh air blower.

ernestedward · 02:02 PM

Blower motor is new, I checked the switch a few days ago and it was fine. Do I still need to replace it? The relay is good. Yes, I have the proper voltage at mid rpms.

Edit: Just to recap: I have 8V at the motor at all positions. Relays and fuses are good. Motors runs when it gets 12V. I really think I'm down to the switch. I'm going to pull the center console tomorrow and see what I see.

SoCal Driver · SoCal Driver's Garage

If you put a new resistance bridge on it you may have rewired it wrong. Jumper the battery directly to the resistance bridge bypassing the switch. Test all resistances.

ernestedward · 12-31-2004, 07:26 PM

It's the original resistance bridge. Good idea though, it never occured to me to jump right to the bridge. I'll try it tomorrow. Could be corrosion or something.

SoCal Driver · SoCal Driver's Garage

As to the switch; mine was bad and still indexed/turned. Would only work on the high setting. Taking it appart showed that the heavy contacts had melted into the backing. I found the resistance bridge to be bad after I put a new switch in it.

ernestedward · 01-01-2005, 08:37 AM

Put 12V to each prong of the resistor, got nothing but a few sparks. Is this indicative of a bad resistor? Am I correct in thinking that I bypassed almost everytyhing, and that there's nothing else that would prevent the fan from running when I do this? Fan motor is definitely good.

SoCal Driver · SoCal Driver's Garage

Sparking.

If you don't have the proper electrical diagrams down load these at Pelican Parts. They are for the early chassis.

http://www.pelicanparts.com/944/electrical/944_electrical_diagrams.htm

This is the diagram for the blower.

Note that you have to provide power to one side of the motor and ground the circuit AFTER the resistance sections to get the fan to run at different speeds. There is also a relay involved. Two if you have A/C.

ernestedward · 01-01-2005, 09:12 AM

Yeah, sparking since I didn't have switched 12v, I just had to put the jumper wires right onto the prongs from the battery. I was trying to point out that the circuit was being completed, that is to say that the ground was good. Should have been clearer. Thanks for the diagram, I'll try again.

ernestedward · 01-02-2005, 09:12 AM

OK, working - Don't ask me how. Just kidding - sort of. After a lot of mucking around and checking and eliminating stuff, I found the problem had to be on the relay side of the blower. Took all the relays out, cleaned them once again, checked them, but when I put everything back together I got an inspection mirror and looked at all the wires on the back and jiggled them. One was slightly loose, pushed it in. Once I put the negative back on the battery, the fan came on immediately. The switch and resistor pack were OK after all. Thanks Hugh.

SoCal Driver · SoCal Driver's Garage