Help with identifying this capacitor

[Jim_S]

Hi Everone!

I have a question on finding a replacement for this capacitor. I believe this to be an aluminum electrolytic capacitor and was used in the early 1970's for an automotive low fuel relay. When the fuel sending resistance dropped below 30 Ohms, this relay would oscillate a dash board light bulb with a red lens printed as LOW FUEL. No problem rewinding the burned coils, but I am having difficulty with all of the numbers show on the capacitor to be able to find this replacement. The physical size is approximately 1" wide x 1/2" high x 3/8" deep. This circuit board fits into the metal mounting frame, so size is an issue.

I believe I understand the markings as:
.5 - ?
+- 20% Tolerance
85C - Temperature Rating
200 V - 200 Volts
900 - ?

Any help identifying the two ratings that I show with a ? and a correct replacement would be greatly appreciated! The impedance on one of these working capacitors is -100 Ohms.

Here are some pictures...





Thank you,
Jim

 

[davenn]

hi Jim
welcome to EP

0.5 uF ( microfarad)

The 200V is likely to be the max continuous working voltage and the 900 is possible the peak voltage

no its not an electrolytic. its an old style polyester ( non polarised ... in this case ignore the red band, it isn't a polarity indicator)


Dave

 

[Arouse1973]

0.5uF never seen one of those before. I guess 470nF is your best bet?
Adam

 

[73's de Edd]

.

Sir Jim_s . . . . . .


Now if this unit does not "cycle" the lamp(s) for you, are you familiar with its basic principle of operation ?

Your photo seemed to concentrate on the cap and I could not see the center pf the photo . . . . . therefore.

I suspect your capacitor VERY-VERY-VERY unlikely of having any fault at all , unless its end leads have become "uncrimped" to its internal foil.

Its basic use here is just as an arc suppressor of contact actions and minimizing any RFI burst to your car radio.

The far right strip, or the one beside it, is a bimetallic strip of side by side different metals that exhibit differential coefficients of expansion,
It is insulatively over wound with nichrome wire to act as a heater to warm up those internally contained metal.strips as the units heat the strip "warps"
and cause the contacts that they are series attached to . . .separate.
Their switch contact action is then opened, and as the strips slowly cool, the warp reverses to let the strip move back to make contact again.

That different heat/metal flex/ contact action makes your slow time constant for the on off action of the unit.

Give a close up of the central unit and more detail / data can be made out as the almost central unit also looks like it has a resistive overwind also, but may
have ran MUCH hotter over time and heavily darkened that covered area.

I currently can't comment on the far end pair without a more detail photo being provided.
There is probably a wirewound resistor involved, being in series with the fuel gauge meter.

? ? ? ? is this a 12 V or an older 6 V battery vehicle . . . . and its brand ? ? ? ? ?.

From my interpretation of auto parts numbering would this be a 1957-58 year model ?

I don't believe that the roll of insulated COPPER wire will be involved.



73's de Edd



.

 

[davenn]

.

Sir Jim_s . . . . . .


Now if this unit does not "cycle" the lamp(s) for you, are you familiar with its basic principle of operation ?

Your photo seemed to concentrate on the cap and I could not see the center pf the photo . . . . . therefore.

I suspect your capacitor VERY-VERY-VERY unlikely of having any fault at all , unless its end leads have become "uncrimped" to its internal foil.

Its basic use here is just as an arc suppressor of contact actions and minimizing any RFI burst to your car radio.

The far right strip, or the one beside it, is a bimetallic strip of side by side different metals that exhibit differential coefficients of expansion,
It is insulatively over wound with nichrome wire to act as a heater to warm up those internally contained metal.strips as the units heat the strip "warps"
and cause the contacts that they are series attached to . . .separate.
Their switch contact action is then opened, and as the strips slowly cool, the warp reverses to let the strip move back to make contact again.

That different heat/metal flex/ contact action makes your slow time constant for the on off action of the unit.

Give a close up of the central unit and more detail / data can be made out as the almost central unit also looks like it has a resistive overwind also, but may
have ran MUCH hotter over time and heavily darkened that covered area.

I currently can't comment on the far end pair without a more detail photo being provided.
There is probably a wirewound resistor involved, being in series with the fuel gauge meter.

? ? ? ? is this a 12 V or an older 6 V battery vehicle . . . . and its brand ? ? ? ? ?.

From my interpretation of auto parts numbering would this be a 1957-58 year model ?

I don't believe that the roll of insulated COPPER wire will be involved.



73's de Edd



.

he only needed to know about the capacitor Edd

 

[Jim_S]

First off, Thank you all for your replies and not making me feel like a penny waiting for change asking this question!

Yes, this is from a 1970 Dodge Challenger equipped with this low fuel option and is a 12 volt system. I was unsure of how to read the 5 as picoFarad, milliFarad or microFarad without any description printed on this capacitor.

I have rewound many of these which usually have a burned/broken wire wrapping, but none without some impedance reading at around -100 ohms. This is what is leading me to look into this further to try and find a replacement.

Seeing that this is an "old school" polyester cap, are there any recommendations for the type of replacement, such as a metalized polyester film cap?

Here are a few more pictures of this circuit board compared to a working circuit board. Yes, we are taking a trip back to analog land with even adjustment screws for the two contact positions. I did circle where this current circuit board wiring is open and needing replaced. Also is a test video instead of using a fuel tank sending unit, I cheated with a variable speed wiper switch from that time period to trigger the low fuel relay to work so you can see what it does. That was recorded a number of years ago, but you can see the center arm wiring was rewound.















Video testing


Thanks again, everybody!

Jim

 

[davenn]

Seeing that this is an "old school" polyester cap, are there any recommendations for the type of replacement, such as a metalized polyester film cap?

yeah, good as gold ... you will find that 0.47uF is the closest preferred value closest to 0.5uF

Dave