Testing Eberspacher BA4 heater parts

[raygreenwood]

Ok...some good thread on this already...but I need some help and would like to get everyone's methods in one thread. Not just a heater rebuild thread, those threads stand on their own but we can link to them here as well. This is specifically for methods of testing heater parts.

So...the week before last...Bob...titan3c...sent me his 411 gas furnace ignition coil and glow plug to test. I said sure! ...forgetting the small fact that my heater while still in teh car...is not operable because I cannot put power to the car right now (lots of loose components).

OK....I will post pictures in the am of what "I" and doing.

So....with a "normal" ignition coil....I can get a pretty good idea of the condition (if I know the coils resistance)...but connecting the VOM between the + and - pins and testing resistance. This is usually the primary coil circuit.

The secondary...you put the red lead on the + connection to the coil and the black lead to teh high voltage output (where the spark comes out)....getting a resistance reading there as well.

On a standard ignition coil like say a Pertronix 0.2 ohm....the primary might read 0.2 ohms...and the secondary might read 5,000 to 10,000 ohms.

HOWEVER: I have four coils...one is known to be bad and is marked a bad. That one reads "0" resistance and "0" continuity. In other words it has a short inside.

Two of my "possibly" good coils both read close to 50 ohms between positive and negative pins...but slowly drop off to about 2.5 ohms. Ok.

Bobs coil....starts out at 50 MEGA OHMS...and drops down to nearly "0". That tells me bad insulation, corroded wires etc.

So the way I am going to test these two parts ...away from the heater unit...is to take a standard distributor with points, hook it up to 12 volts and use the points and condenser to fire the heater coil. I will do the same for the glow/spark plug.

The glow plug section, I will hook up to + and - with my amp meter in between....make sure the coil glows and make sure its not pulling more amps than the book says.

We will see if it works...but any input on what you have successfully read or measured from heater parts is welcome!
Ray

[Lars S]

Ray, I think you are on thge right track!
Only, for testing the coil I would use a separate BA4 Fan unit instead of a dizzy so that the condenser used is matched to the coil. The condenser seems to be built in in the fan housing. (or use that condenser in the dizzy)
I would hook it up as shown below, only connect the colored wires:

Green - ground/earth/-12V to fan unit and spark plug
Blue - from coil no1 to breaker points.
Red - +12V to coil 15.

If you have the BA4 condensor loose you could (as shown below) just have the condenser connected from coil (1) to ground and simulate the points by connecting another wire to coil (1) and touching its other end to ground. (Also +12V to coil (15) and ground to spark plug should be wired of course).

/Lars S
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold

[Hawker]

Gents,

If it is any help; when I bought my first 4 door 411LE on the rear parcel shelf was a Bosch blue 12 volt coil. It was connected to and provided the HT for the glow/spark plug of the BA4.

You don’t have to use a condenser from the system, any condenser of similar capacity will be fine.

BR,

Rob

[Lars S]

[raygreenwood]

[titan3c]

Wish I had known. I could have sent my blower unit too, and still can. Bob

[titan3c]

Also I can send the complete heater if that helps any.

[raygreenwood]

Titan3c....sory I did not get back to you and sorry this is taking so long. Should have your parts back by end of week.

I am just getting a test network set up with one of my bloer motors. As Lars and others have mentioned...its not a big deal. Power t the motor with two pins and power THROUGH the points (ground I believe.

On a similar note....opening up one of my motors for the first time in a long time.....I am reminded....that decades ag when the capacitor died on one....I was never able...in pre-internet times...to find a "replacement" capacitor.

A lot of this was because not having any connections yet in high school and college....I was stuck with a few very basic local electronics repair shops.

When i took the offending part in....they looked at the numbers and noted "yeah...I think that means a 0.15 mfd capacitance at 400 volts".....but not being able to be sure...and the part already being very old looking and alien in the early 1980's....they noted that they really could not recommend anything.

So I was stuck with going to the junkyards and acquiring complete furnace motors....which is actually a good thing to have spare parts.

So now....with this cool interweb thingy at my disposal.... .....I have looked up this part:

This is a WIMA Durolit "film" capacitor.

Its is 0.15 microfarad and rated at 400 volts.

And....yes...they are available here and there...but are listed as "rare" and vintage" and are used in musical instruments and amplifiers.

So....if I were everyone....even though these rarely have issues.....look up one or two on Ebay and buy a spare or two.

Yes...I'm sure a modern one could do fine...but may not have th form factor.

I am finding them for prices like $39 for four NOS...or about the same $9 each used.

More to come on the testing in a day or so.
Ray

[raygreenwood]

OK….so the reason why I asked about INDIVIDUAL component testing….instead of just looking in this excellent Samba thread about restoring a gas furnace…..

https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0

…is because while it has been commented that the best way of quickly testing components is to hook them into your system and turn them on….however….that assumes your car has power right now, your system is installed…..and most importantly that everything else in the system is working.

If you have a switch, temp sensor, relay or wiring component that is not up to snuff…testing fuel pumps, coils and glow plugs can cause you to think the components are bad …when in reality it’s something else.

So this is going to be about testing (mostly) coils and glow/spark plugs….with only test wires, a 12 volt battery and an operable blower motor….but you can test the fuel pump this way as well.

If you can pull just the blower motor off of the heater or if you have a spare, you can test all of this.

You need a few wires and some clamps and you can use the battery in your daily driver to check all of this.

Some maintenance issues first. There is a pair of trigger points in each end of the blower motor. Those must have clean contacts, properly gapped points and an operating condenser. And yes….its common that those condensers burn out. Back when I had my first 411 in 1978…I went through two winters having no idea why I could not get the gas heater working before I discovered this issue.

I am sure you can use a regular electrolytic capacitor (ceramic or aluminum)….but they came with “film” capacitors. You can still get the original kind of NOS…a bit expensive…but I will post part #’s for both old and new types.

When I started testing recently …this bit me again….as one of my spare blowers had a dead capacitor….and I had to dig out a second spare motor to continue….I suggest that those who want to use their heater regularly should buy a couple of capacitors and solder them in as new for good measure and keep a couple of spares.

So…start with good capacitors, clean and gapped points in the blower motor.
You can find a lot more detail on rebuilding this whole system in this thread below.

An important question:

How did I know I had a burned-out capacitor (really, it’s a condenser)? I found out by accident!

I hooked up my test wires, fired up the blower with a coil and glow plug connected….no spark. Tried five glow plugs. No spark. Tried all four coils I had at hand. No spark…..but…..as I reached over and pulled the positive clamp off of the battery, shutting the blower motor down…..I saw about 3 quick sparks jump.

So I put the connection back on the battery….no sparks….pulled it loose and saw about three sparks jump.

Aaaaaah!....weak capacitor/condenser. Here is a quick “what is” about capacitors and film capacitors:

https://www.electronics-tutorials.ws/capacitor/cap_2.html

What was happening is that the film condenser…..which is a rolled up sheet of dielectric film inside….is shorted or has cracked dielectric between the film layers…allowing the wire to short to ground all the time when current is applied. So even if the points are cycling…..its staying in constant contact so the coil never cycles. Turning off the power…breaking the connection…somehow bypassed this enough to get a couple of sparks.

I am not explaining it well….but that’s the issue. If you want a little reading about why capacitors fail….this is good.

https://arxiv.org/ftp/arxiv/papers/1607/1607.01540...%20factor.

In short…age alone can cause this…along with moisture that’s inside from production, leakage or excessive heat etc.

So…I grabbed another spare blower and tried that one…..and the first coil was bad but the other three sparked just fine. All of the glow plugs were good.

The other issue is this. I had to kind of ask myself why they opted to use an odd (to me) “film type” capacitor instead of the normal silicon or electrolytic capacitor that was more common even back then….and if you read a little bit in those links…I think we find out why.

The same reason why the condenser on our distributors are actually film type condensers. Rolled, dielectric sheet type film capacitors can be made to handle much higher voltage than standard silicon or ceramic types capacitors …in small packages.

These are 0.15 microfarad at 400-volt capacitors. If you even try to Google 0.15 mf X 400v capacitors…almost all sites like digi-key will automatically ONLY list film capacitors. I believe the voltage of the coil is why a high voltage capacitor is needed.

So…the blower motor has a rubber boot cover on the outside end with the electrical plug on it. Remove the rubber boot. Underneath is a metal cap held on with a single screw. Underneath that cap is the ignition point set for the coil and glow plug/spark plug. You will see the gold-colored film capacitor right there.

The gap is .016”.

You do not have to have the cap off while testing but you should remove it to at least check the connections, file the points and clean them and check the gap.

The fuel pump trigger points are at the other end of the motor. You remove the aluminum vane ring cover. Then through the access hole you use a 2mm Allen key to remove the fan/impellor. Then you can remove the large snap ring and slide the motor out of the aluminum shell. Remove the rubber ring on the end and there is a single screw that holds the cap on.
Same process…points set to 0.016” and clean, lube and check connections.

As I noted this is not a detailed thread for anything but a quick component test with nothing but blower, battery and a few wires.


So here is the blower motor, four pin plug:

Notice that it has an alignment tab or lug. I am simply putting that at 12 o’clock for easy sketch. You can see what each pin goes to. It’s a simple + and – for the motor and a single wire to each set of points for fuel pump and coil that goes to the switched or moveable side of each point set.

The coil and fuel pump both have their + lead connected directly to them. The two wires, one to each point set….simply connects each component to ground each time the points close.

First…I suggest getting a piece of board or table to do your testing on. If you have a work bench and a spare 12 volt battery you can just set the battery on the bench. I teste mine under the hood of my Golf so I just laid a board across the top of the engine. Yes it looks crude but worked great!

So, a little bit about test wires. I believe the pins in the four-pin plug are Molex style, round pin. You should measure yours but mine are the 2.13mm (0.084”) diameter variety. They also come in 0.062” and 0.093”.

You can get the female connectors in some auto parts stores, from Digi-Key on line and at virtually any hobby store that sells RC cars and airplanes.

If you go to the local hobby stores…which is the fastest, cheapest way to get these… you are looking for “Tamiya” style connector pins and plugs. Dirt cheap and quick locally. Get about six of them. You need a crimping tool that works for fuel injection terminals.
Yes, you can do them with small pliers…crudely…but DO NOT solder them. It screws them up.

These…fit. A little tight but they expand. Our pins measure about .082” to .084”. The male pins that came with the female pins and plugs measure 0.080”..so a little tight but they fit.

https://www.hobbytown.com/racers-edge-tamiya-type-connector-plugs-rce2480/p35608

By the way, the Hobby town chain is what is left of Radio Shack. They still have a lot of stuff but most of it is aimed at people building wiring for LED hobby work and the RC toy industry.

Also, by the way…Molex round pins are common, easy to get, cheap and carry a lot of current…but they are SHITTY connectors for automotive and aircraft. They work the same way as a D-jet connector. They are not sprung and they wear and get loose.

So….if you have had intermittent issues with your heater, get some new female terminals, pull the wires out of your heater blower plug one by one and crimp on new ones.

My test wires:

About 20 gauge hook up wire is fine.

Ground cable from battery negative to spark/glow plug body:

I bought these two spring clamps at Wal Mart for about $2. They came as a pair. This is just a ground clamp for the glow plug body straight to the battery negative.

Ground cable from battery to motor negative (one lead or you can incorporate the lead to the glow plug body with this one)

Positive cable from battery to motor and coil (two leads):

This is simple. Big spring clamp to the + battery terminal. It has two equal length wires crimped to it. One with a standard female terminal that goes to terminal #15 on the coil. The other lead is a round pin Molex female connector that goes to the pin at about 4:00 o’clock position (with reference to the locating lug) on the blower.

Negative cable from battery to blower motor supply pin.

This is also a spring type battery clamp. You see only a single lead wire in this picture but there are actually two. You only really need one. This brings battery – to the 7:00 o’clock pin on the blower motor so the motor itself will run. I used two simply in case I wanted to test the fuel pump and coil at the same time.

NOTE: this also gives negative to the entire blower motor chassis and is where both the coil and fuel pump get their ground from as the points open and close.

Negative wire from ignition coil points pin in motor plug to coil:

This is just a standard female terminal to connect to terminal #1 of the ignition coil and then to the breaker points pin at about 2:00 o’clock on the motor plug

So…let’s say we are going to test the coil first. Here is the wiring schematic you need:

Make note!...you must connect the motor positive and negative correctly or the motor will run backward. I do not think that changes anything spark wise but its good practice to have it right.

And…either tape the motor down with duct tape or block it so it does not try to rotate. It has a lot of torque and will take off!.

When the motor runs connected like this…the coil operates and the spark plug sparks. Once you know you have a good coil you can test all of your spark plugs this way. Or…now once you have a good spark plug you can test all of your coils this way.

Testing a fuel pump wiring schematic:

Testing the glow coil is a little more involved. Its dead easy to test if it just glows. However, they…the heater manual… want you also to make sure it does not pull too many amps or I “think” it may blow the safety circuit or may be one of several things that can. Don’t quote me on that yet.

I hate the way the book explains this. First…I do not JUST want to know what the maximum amperage consumption rating is. I want to now what they consider ad “nominal” or normal…or correct amps rating is. They kind of say this….but.

Here they are testing the current draw with an Ameter. I do not have an Ameter. I have a digital VOM that has an “amps”, Milliamps and microamps dial position. My amps dial position can allow up to a 20 amp pull for 30 seconds.

The object is that you put the VOM or ammeter connected to the + current supply with its + probe….and the negative to the positive feed pin of the glow plug coil. The body of the glow plug gets connected to the negative side of the battery. So you draw the + power through the ammeter or VOM so you can read how many amps you draw.

One would think that you would connect the negative battery wire to the negative flat terminal on top of the glow plug….but they show instead connecting it to the body of the glow plug like it would be grounded when screwed into the heater chassis.

If you look at wiring diagram…that negative tab just goes to ground…so they should be the same thing.

Anyway…they note 5.5 to 7.0 amps is normal and that 8 is too high. Maybe ammeters are that different….but I read exactly 0.15 amps on each glow plug and in different mode 1.5 amps…..exactly. Still looking into that.

I hope this helps!
Ray

[Pepperbilly]

Ray,

This is excellent stuff! The timing is good because that is where I’m at right now. Everything out of the car. But today I think I’m gonna start on cleaning out the fuel tank. Want to get that done so I can install it back into it’s nesting place.

Bill