I had this problem from the beginning. Voltage drops below 12V when moderate amount of electrical instruments are in use. It badly effects idle speed. It drops 900-1000 to 500-600. It gets harder to move the car from full stop at the hills without stalling the engine. Sometimes I have to press both pedals with my right foot like rally drivers or use the hand brake.

 

Long story:

I had this weak electrics problem from the beginning. So I installed a voltage gauge on the dashboard to monitor the situation. The car had some unacceptable mistakes to the electric system made by previous owners. I've replaced some of the connectors and cables. Corrected some wrong connections. Completely overhauled and reinforced the fuse box. None of these improvements totally solved the problem.

 

Two weeks ago when I started the engine, I saw 17V from voltage gauge! I thought voltage gauge is showing wrong. It's a $1 part after all. I checked with multi-meter and it was right. Voltage was crazy. Luckily, I've read somewhere here about alternator problems. I already know that it's voltage regulator fail. So I turned on headlights, both fog lights, interior ventilation to max, rear window heater, radiator fan. With almost everything on the voltage stabilized at max. 14V at 2000rpm. I went to the nearest parts store and bought a new voltage regulator. So a $1 voltage gauge saved me from lots of troubles and probably lots of damage.

 

So I have a new voltage regulator too. I hoped this would helped with the low voltage too but it didn't.

 

Current state: If I turn on headlights or front fog lights (55W x 2) + interior ventilation (2nd or 3rd level doesn't matter), voltage goes below 13V. When radiator fan kicks in, voltage drops further to 12V. After that, it gets messy. If it's raining and I have to use the wipers, voltage drops to 11,5V! When I use blinkers voltage is dancing between 11.8 and 12. Anything below 12.5V heavily effects ignition thus idle speed and that creates the real annoying problem. Engine creates vibrations because of low idling speed and becomes very prone to stalling at initial moves going uphill.

At the daytime there is no problem. Voltage will always be between 13.5 and 13.9. (All readings from dashboard source)

 

I've already tried bypass cables directly from alternator to battery. Didn't have an effect.

 

Old voltage regulator:

 

New voltage regulator:

 

Alternator itself:

 

Condition of the slip rings:

 

I can find diode assembly from local stores but I can't find any info regarding slip rings. Are they replaceable?

Edited 9 September, 20214 yr by R_Blue
Typo

Can you maybe try cleaning up the slip rings with a small wire brush?

I've replaced them on one or two alternators, so it can't be too difficult - if you can find them as spare parts to suit your model.

8 minutes ago, Wino said:

Can you maybe try cleaning up the slip rings with a small wire brush?

I've replaced them on one or two alternators, so it can't be too difficult - if you can find them as spare parts to suit your model.

Thanks for the quick reply. 🙂 I will try cleaning the slip rings.

I'd check diode bridge, it's pretty common that one or more diodes blow and alternator cannot reach full power.

Well either you have an inefficient alternator or burned up diodes 

Let's start with the basics. What is the status of the battery? Think objectively.

Thanks for all the help.

 

What I've tried and found s far:

 

All my previous voltage observations are from a voltmeter installed in the dashboard and not directly from battery terminals.

 

On 10/09/2021 at 22:36, RicardoM said:

Let's start with the basics. What is the status of the battery? Think objectively.

The battery is a huge 72Ah. From a reputable local producer. Production date is 05-2018. Sealed type.

 

Engine off battery measurement from battery terminals shows 12.7V.

While engine is running at idle with no load, voltage is 14-14.2 max.

While engine is running at idle and If I turn on electric appliances of the car, voltage drops to 12.3V (interior voltage meter shows this value much lower)

 

I tried running a parallel cable from alternator body to battery negative.

I tried running a parallel cable from alternator positive to battery positive.

Voltages remained same. No effect.

Voltage measurement from ignition coil 12V supply is like 1V lower than battery terminal.

 

Running a parallel cable from battery to ignition coil have raised the voltage. So there is a high resistance connection.

I removed all fuses from the fuse box and opened the ignition and there was still a voltage reading. That means car's original ignition supply is not fused!. I used a 15A fuse and a relay that feeds the ignition directly from battery. This raised the ignition coil voltage by 0.5V but still not satisfying.

I haven't cleaned the slip rings yet.

 

I will update this topic with more findings.

8 hours ago, R_Blue said:

The battery is a huge 72Ah

Why?
Haha

3 hours ago, Thefeliciahacker said:

Why?
Haha

This was on the car when I got it. Maybe there was a discount on large batteries? All I know is, it requires two people to maneuver and lift it from its place in the hood. 😱

12 hours ago, R_Blue said:

I haven't cleaned the slip rings yet.

I would do this next, if I were you.  I think your (excellent) measurement data suggest that the problem is that the alternator simply cannot generate sufficient current to keep up with demand when there are heavy consumers switched on.

If the field coil current supplied through the slip rings is limited by poor connectivity, it will automatically limit the maximum output current from the alternator that is available at any given rpm.

 

They look corroded/dirty in your photo I think.

 

Edited 16 September, 20214 yr by Wino

On 16/09/2021 at 10:25, Thefeliciahacker said:

The battery is a huge 72Ah

Yes but your old altenator can charge sufficiently that big Ah battery?

It really doesn't make a big diffrence maybe a couple of more amps when the battery is charged

First of all sorry for the late reply. This problem have turned into an bottomless abyss. It took lots of work and trial&error because of inconsistencies.

Also I had to deal with:

- Completing painting car's bottom with anti-gravel before rain season.

- Leaking freeze-plugs.

- Leaking exhaust from manifold output connection.

- Restoring sound system speaker connections. (Considering it as a luxury, I haven't touched the sound system since I bought the car in January. The car stereo wasn't even connected and sitting in the house. Now it's partly working.)

 

Now to the topic:

On 17/09/2021 at 23:08, D.FYLAKTOS said:

Yes but your old altenator can charge sufficiently that big Ah battery?

I think if enough time is given to the alternator at light load (day time), it will charge it eventually.

On 16/09/2021 at 14:03, Wino said:

I would do this next, if I were you. 

I concentrated all my effort to clean the slip rings. I couldn't find a proper tool to clean them without taking the alternator off. So I improvised a cleaning tool.

I glued pieces of sand paper to the tips of the old voltage regulator's brushes. Exactly the same size of the tips. Mounted the voltage regulator in its place and fired the engine. (all alternator cables disconnected) I let it run for 10 seconds. The result was %50 successful. One slip ring was cleared but the other one wasn't. Voltage change was negligible.

I took out the alternator for better examination and cleaning the slip rings. Condition of the bearings was bad. They were making clicking sounds when rotated. There was a charred bee in the diode array too.

For testing purpose, I cleaned the slip rings properly and tried again. Voltage output was increased! But still not acceptable. :(

I took out the alternator again.

I decided to make a complete renovation of this alternator. So I bought a new diode array.

This one is a universal diode array compatible with 3+1 bolt connection. I think the extra bolts with cables are for Felicia 1.9D. (Tachometer feed?)

I removed the cabled bolts by cutting their cables from the bottom. There are two D+ connectors compatible with other alternator bodies that don't have a separate D+ connector platform.

I cut one and bended the other to opposite side of its natural direction to direct it towards the D+ connector platform of the old 55A Škoda alternator. I soldered the stator wires and the D+ platform wire.

I cut the male connector at the bottom before assembling.

I don't have the tools for bearing change so I took my alternator rotor to a machine shop. I've been told that slip rings are actually in good condition. Cleaning them was enough. So they replaced the bearings.

Main bearing is a 6303-2RS. Secondary bearing is a 6201-2RS.

Main bearing is secured in its place by three rivets.

After all of these, I assembled the alternator. With great anticipation I installed it in its place to test the voltage AAANNNND.... It didn't work. 😞 No output from alternator. This left me with nothing but battery power. I decided to visit an alternator specialist for a test bench. I drove there on battery power. I took out the alternator for inspection. The technician placed the alternator on the test bench and guess what happened this time? It was working! He tightened the nuts of the diode table and gave me the alternator back. When I installed it, it worked this time! Luckily, the specialist didn't charge me for this. After going home, I replaced the flat washers under the diode array nuts with serrated lock washers.

Finished?

NO!

Inconsistencies with the electrical system continued. 😞

It almost drove me mad after all I had done. The only thing left is the main cable and connectors. So I bought 6mm cable and replaced original cables from factory. Wiring loom is wrapped with insulation tape. One must unwind the insulation from firewall side to the far side ends with alternator connector. Also you should dissemble the glove box for ease of access to the interior side of the firewall. Main cable is divided into two near the battery. One end goes to battery, the other end goes to the fuse box and connected to the fuse box with a bolt and nut. I made the division at the fuse box connector by joining them together to the ring connector. I reinforced all ring connectors with solder by covering all bare copper cable ends at the clamps.

 

I'm glad I did this. Because I found THE FAULT! The damn, terrible fault was the damage on the cables.

There was additional foreign insulation over this part. So an owner before me had faced this problem. Someone knew this damage, but instead of fixing this, they had just taped it. You see the green dust already in the cable. That means copper had corroded from inside.

The cables in the picture are main cable from alternator and the missing radiator fan cable. There is another story unfolded here. When I bought the car, original cable that must be coming from fuse no7 was missing. Now I've found this inside of the wiring loom laying damaged. I think, because of this damage, the radiator fan had became dysfunctional in the past. Eventually this could have been ended with this car's first overheating, followed by head gasket failure. They all knew this but didn't fix it. 😞

So, after alternator renovation and cable replacement new voltage readings are: (taken from hot engine)

Battery terminals at idle: 14.16V. Full load: 12.5V

Alternator terminal at idle: 14.24V. Full load: 12.72V

Battery terminals at 1500rpm, full load: 13.64V

Alternator terminal at 1500rpm, full load: 14V

 

Turning everything on at the same time is a rarity. I used the car with night time regular conditions which was problematic before. Now the low idle rpm problem is gone. idle rpm is still affected from extra electrical loads like headlights, interior fan and radiator fan working together but it's not as much crippling as before.

 

I did a little research for same era cars with similar alternator capacities. Some had higher rated alternators later years. I think 55A is the bare minimum so efficiency is very important. Whole electrical system condition is critical for achieving best efficiency and getting the most from your alternator. This includes all cables and connectors. If I had bought a 70 amp Felicia alternator before dealing with damaged cables, I would still suffer problems.

 

Now I can live with my renovated alternator. Thanks for everyone contributing to this topic.

On 15/09/2021 at 23:51, R_Blue said:

I tried running a parallel cable from alternator positive to battery positive.

Voltages remained same. No effect.

This test should really have found this problem, I'm not sure why it didn't improve things; can you remember what thickness the parallel cable was, and length?

 

When you say 6mm cable do you mean 6mm²  cross-sectional area? If so that sounds thinner than I would choose if I were fitting a replacement cable.  I would go for at least 10mm² if not 16.

 

Well done for your persistence and eventual success. 

Edited 5 October, 20214 yr by Wino

Well done you and its nice to see someone else repairing rather than replacing an alternator even if it did not turn out to be the fault.

On 05/10/2021 at 16:34, Wino said:

This test should really have found this problem, I'm not sure why it didn't improve things; can you remember what thickness the parallel cable was, and length?

The problem was combination of various flaws of the whole system. I did this test before cleaning the slip rings and it seemed like it didn't work. I cleaned the slip rings later but I tested without those parallel cables. 😞  The problem has eluded me this way.

On 05/10/2021 at 16:34, Wino said:

When you say 6mm cable do you mean 6mm²  cross-sectional area? If so that sounds thinner than I would choose if I were fitting a replacement cable.  I would go for at least 10mm² if not 16.

I remember 6 was written on the cable reel in the hardware store but not sure if it was mm². It's the same as factory cable or thicker but absolutely not thinner. I'll check the exact value.

On 05/10/2021 at 16:34, Wino said:

Well done for your persistence and eventual success. 

Thanks! This means a lot for me.

 

On 05/10/2021 at 17:45, J.R. said:

Well done you and its nice to see someone else repairing rather than replacing an alternator even if it did not turn out to be the fault.

Thanks!

The bearings were in a really bad condition. Finding that before anything worse happens was good too.

 

Also, I've been told that, aftermarket alternators for Favorit/Felicia were too unreliable. When renovated, original Škoda alternators are wiser choice.

10 hours ago, R_Blue said:

I remember 6 was written on the cable reel in the hardware store but not sure if it was mm². It's the same as factory cable or thicker but absolutely not thinner. I'll check the exact value.

Felicia stater is 1kW which means 80amps at a moderate cable length of 1m 16mm^2 is the proper thing to use.

 

10 hours ago, R_Blue said:

When renovated

correctly I may add

52 minutes ago, Thefeliciahacker said:

Felicia stater is 1kW which means 80amps at a moderate cable length of 1m 16mm^2 is the proper thing to use.

Starter cable in my car is a separate one which is thick like a thumb.

https://pasteboard.co/KeXBGYf.jpg

You mean I need another one between alternator and battery?

4 hours ago, R_Blue said:

You mean I need another one between alternator and battery

Well no you are fine I got confused

On 05/10/2021 at 16:25, R_Blue said:

Because I found THE FAULT! The damn, terrible fault was the damage on the cables.

 

 

 

Different case-same cables problem. 😁

 

On 07/10/2021 at 02:25, R_Blue said:

I'll check the exact value.

Today I went to the hardware store where I bought the cable with a piece of old cable from the car with me. I compared them and they have the same thickness. Right designation is 10mm². They sell it regarding cables' outer diameters.

 

On 07/10/2021 at 19:01, Thefeliciahacker said:

Well no you are fine I got confused

That's a relief.

12 hours ago, D.FYLAKTOS said:

Different case-same cables problem. 😁

When this was happened? So there is a friction point or another mechanical force causing this. I must reinforce that part.

10 hours ago, R_Blue said:

When this was happened? So there is a friction point or another mechanical force causing this. I must reinforce that part.

 

A mechanic which make a correction to the radiator cover push some cables more that it should be, the tie-wrap broke and those cables rolled down

The pulley belt touch and ruin them, i discovered the problem when i was on the run (burned fuse plus no lights) and next day i had to go to the electrician to make an extension and secure them tightly.

3 minutes ago, D.FYLAKTOS said:

the tie-wrap broke and those cables rolled down

The pulley belt touch and ruin them

That explains everything. Original tie-wraps at the right side in my car are are also missing. Cable bundle is secured there with wires.

In every modification i have made the last years the rule for the cable is one: Protection

No matter if its spiral or heat shrinkable cover i never let cables unprotected.

I have bought such materials from hardware store (in case that i am working by my own) and every-time i go to the electrician the last remarks is ''cover every cable".

2 minutes ago, D.FYLAKTOS said:

''cover every cable".

I also think, uncovered cables are prone to corrode from inside. I've encountered unprotected and undamaged cables rotten inside. I think normal cable insulation is not weather-proof.