Anatomy of The DC/DC Converter

ddoxey · **Joined:** Mon Feb 20, 2017 7:53 am **Posts:** 55

I picked up a used DC/DC converter on ebay.

Today I dissected it.

Mounted to the sides are two circuit boards.

This smaller board on the side holds two Bussmann FWP-40A14Fa diodes -- presumably the ones that burn out when the cabin heater craps out.

On a final note, here's a little connection diagram:

Philly RAV4 EV · **Joined:** Fri Apr 26, 2013 1:45 am **Posts:** 85

That's interesting.

Aries · **Joined:** Tue Jan 08, 2013 6:09 pm **Posts:** 49

Very cool. Sure looks serviceable to me... socketed and all.

Thanks for sharing this!

TonyWilliams · **Posted:** Tue Apr 25, 2017 2:39 pm

Awesome work. I'll be pulling one part next week, with a blown diode.

ph2 · **Joined:** Tue Apr 25, 2017 6:23 pm **Posts:** 21

Bussmann Semiconductor Ferrule Fuse, hence the odd symbol. Very interesting, thanks for sharing!

Here is a link to more detailed product data from Eaton/Cooper/Bussmann: http://www.cooperindustries.com/content/public/en/bussmann/electrical/products/high_speed_/ferrule/fwp_690v_700v.catalog_numbers_(amps).html

ddoxey · **Joined:** Mon Feb 20, 2017 7:53 am **Posts:** 55

Today seemed like a good time to compare a broken (not powering the heater) DC/DC converter with a good one.

On the Left is the broken unit, and on the right is the good one.

I placed the ohmmeter on the +/- terminals of:
* the cabin heater power: 100kΩ is normal
* the battery coolant heater power: 0.4MΩ is normal
* the AC compressor power: 100kΩ is normal.

It looks like a slam dunk. If you're cabin heater power is an open circuit then you've got a fried diode in your DC/DC converter.

miimura · **Posted:** Mon May 01, 2017 6:07 pm

Can you move the image to a different image host? The image doesn't render for me. When I'm logged in with a Google ID, it shows the minus sign in a circle, whatever that icon is called. When I'm logged out, it shows the forum broken image icon.

Anyway, I would be very interested to see that the DC/DC can be repaired by just changing the diode. The only other thing is how to properly seal the case so it's water tight after repair.

TonyWilliams · **Posted:** Thu Jun 08, 2017 6:03 am

I'm having a HELL of a time with that glued on cover. I must need a hammer ;-)

ddoxey · **Joined:** Mon Feb 20, 2017 7:53 am **Posts:** 55

TonyWilliams wrote:

I'm having a HELL of a time with that glued on cover. I must need a hammer ;-)

I initially approached it like baking open a headlight. But the adhesive is actually very tough, with a very high melting point and having the smell and consistency of inner tube rubber. The manufacturer must be pressing the enclosure cover on at a very high temperature.

I think the best approach is to use a square tip exacto blade and stab through the adhesive one blade width at a time. Be careful to avoid pentarating too deep near the connector pass-throughs.

I haven't reassembled one yet. My plan is to thoroughly remove the original adhesive and then apply a bead of the type of butyl glue used for sealing headlight enclosures. I would then apply clamps and the place it in an oven preheated to 260F for 20 min, just like resealing a headlight.

The butyl glue is not nearly as heat tolerant. But I doubt it gets up to 260F under the hood.

TonyWilliams · **Posted:** Fri Jun 09, 2017 2:06 am

I'm just going to use "gasket maker" to reassemble. That is nutty how that is glued together, with no access to fuses.

My new fuses should arrive in the morning. Swing on by and check out our work! We will be installed a JdeMO both Friday and Saturday morning.

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Anatomy of The DC/DC Converter