[jeyjey]

I must admit that when Rick was talking about cleaning all the relays in his car a few weeks back I might have rolled my eyes a bit.

Fast forward to today when my fans stopped working. Examination of the fan/compressor relay on the O/S bulkhead revealed that the yellow/black wire had a melted plastic shield on it, and the spade terminal it fit to showed some corrosion. I cleaned both the spade and the Lucar connector, but to no avail.

(Warning: the centre C2 terminal of the relay is live even without the ignition on. If you clean with steel wool you're likely to get a few strands of stray wool lighting up as they burn. Probably better to disconnect the battery or take the fuse out from right below the relay.)

Disassembly of the relay revealed that the rivet holding the spade connector to the internal post had loosened. This no doubt produced some resistance, generating a bit of extra heat and quickening corrosion, contributing to further looseness, resistance and heat. I cleaned it all off with a wire brush, re-crimped the rivet with a pair of vicegrips, and then soldered the rivet to the spade for good measure.

Testing showed that I still had several ohms of resistance between the common (C2) spade and C1 with the coil energised. I carefully bent the C1 contact post to align it better and then ran some 240 grit sandpaper between the contacts to face them parallel. I cleaned that up with 400 grit sandpaper and some brake cleaner, and all was well.

I cleaned off the flux from the soldering with acetone, taped over the spade contacts and then sprayed the bottom of the relay with lacquer. I think most of the corrosion was caused by the heat rather than the other way around, but better safe than sorry.

So am I going to go through all the relays on the car now? Umm... no. But I can certainly better understand where Rick is coming from.

Jeff.

 

[guyslp]

Aged relays are a notorious weak link in these cars. I don't know what the price of Lucas relays "of the original style" is "on the other side of the pond" but over here they are obscenely expensive (over $50 each).

All of these have their functional substitute in Bosch-style relays of the necessary amperage ratings. Most of the relays are SPDT, but we have a few SPST. You can directly substitute an SPDT for the SPST and have the same function, just don't hook up anything to terminal 87A [This was done in my car in several places with Lucas SPDT relays used in place of SPST relays].

The attached image gives the pin-to-pin mapping for a Lucas 6RA to Bosch-style relay.

I'll also add that dielectric grease or, better yet, conductive electrical grease is your friend when you have clean connections that you'd like to keep that way for a very, very long time.

Brian

 

[jeyjey]

Hey Brian,

What's the low-down on the electrical grease? Is it something you put on the Lucar connectors to protect them, or would you even use it on the relay contacts inside the relay?

I have some Bosch distributor grease. Is that the same thing?

Jeff.

 

[guyslp]

Jeff,

For myself, I would never open the relay itself since the case does a more than adequate job of protecting from anything other than some slight surface oxidation [at least in most cases]. If you're really looking for an airtight seal there are relays that feature this.

Dielectric grease (which is what Bosch Distributor Grease is) is not electrically conductive and is most often used to seal out moisture where conductivity is not needed or wanted. Many, myself included, use it directly on Lucar/blade connectors on both sides of the connection since the actual contact area in a blade connector is relatively small and the sliding action clears more than enough of the dielectric grease to allow a good connection. I apply a thin smearing to each connection before I put them together, trying to avoid having so much that blobbing occurs after putting the connection together. I've never had a connection not work because of the application of dielectric grease. This is available at virtually any auto parts store and many department stores that carry auto products.

There are those who simply do not want to use dielectric grease at connections (and one should always apply it before sliding things together) because it is not conductive. For anyone of that sentiment there are a wide range of electrically conductive greases available that serve the same protective purpose. One must be a bit more cautious with these as you don't want any stray "blobs" shorting circuits if connections are in close quarters. A web search on [electrically conductive grease] should turn up options available near you.

 

[jeyjey]

Thanks, Brian.

I always wondered what to do with the stuff.

Jeff.

 

[rolindsay]

I laughed quietly to myself as I read the first post in this thread, thinking about the rolled eyes. I now smile quietly knowing that my car isn't the only one with dodgey relays. Mine too are now restored and I have A/C again. That matters when Houston is at 42C!

-rick

 

[jeyjey]

He he... my fans have since died again (or rather, all speeds bar full-on have gone away).

I'm pretty sure that means the fan speed controller is shot. Anyone been into one of those? (I suspect some of the transistors will be NLA and that I'll need to figure out what the modern equivalents are. I see there are a bunch of diodes in it too, so maybe it's just those that need replacing.)

Jeff.

 

[rolindsay]

Jeff, you might make some measurements on the transistors. If they're NPN transistors, 2N3055 replacements are strong enough to handle about anything in this range. 15amp rated, I believe. They're cheap too, US$2.50 or so. I'm sure there's a PNP variant too but I don't know the number. The same device is available in a TIP case, rather than the typical TO-3.

best regards,

-rick