Got dodgy relays? Fix them!

JELG

Over the years I have had an assortment of problems with various Volvo relays. It turns out that the electronics are usually just fine, but for some reason the solder on the circuit boards seems to go crystalline and let go. This seems to be particularly bad on the mounting pins and may be a result of heat cycles and/or vibration. Volvo relays seem to run hot. One of the worst offenders is the overdrive relay on early Auto Trans cars. Those are normally energized and only de-powered when the overdrive switch is pressed. Some people drill small air vent holes in the cover to help cooling. Probably a good idea.

I recently bought a really nice 760 Turbo that had an assortment of relay issues. Principally, the headlight relay was bad. (High beams would not latch on.) On this car, the relays are held in with little clips and were a pain to get out. I had to pull every relay out to get to the headlight relay. So I popped each of them open and inspected and repaired them all. Before I reinstalled them, I ground off the locking nubs so I can get them out much easier if I ever have to.

Here's some pics:

This is the double headlight relay off my 760. Very hard to find in working condition now, and therefore expensive.

Using a small sharp pick you can pry around the edges and pop the cover off.

Here is the board. Not much to see.

But, get hold of a stereo-scopic microscope. Not a binocular microscope. Stereo scopes give a true 3D view. They are cheap on e-Bay and great to inspire kids in science projects. I bought mine when we were home-schooling. But I use it all the time. Even for getting out splinters.

You will also need a powerful soldering iron and flux cored solder. The old solder has quite a high melting point and my cheap iron was only just adequate. You don't want to overheat components by holding your iron on the pin too long, waiting for the solder to melt. You need to do the job quickly. (Check Youtube for soldering hints. ) The boards also seem to be coated in some sort of lacquer. I tried to scrape most of it off before soldering the pin.

Here are few shots of some of bad pins I found. I simply held my smart phone up to one lens on the stereo scope and took the photo. It worked surprisingly well.

Many pins were cracked all the way around, or nearly so, and some were actually loose. I just re-flowed the solder and job done. Headlights now work. So does the bulb failure relay and sun roof. I should have taken a snap of a re-flowed pin, but forgot to.

This was the headlight relay and the pin was loose. Several others were cracked and almost broken free. It all works fine now.

ramrod

You sir are a true repairer

Well done

Major Ledfoot

Excellent photography of the failure points.

It shows what 30+ years of vibration and heat cycling inside a vehicle cabin will do to mass produced electronics that were assembled using wave soldering.

Brad

Thanks for this post. Those photos through the scope are terrific. I've had a few relays with the same failure on my 940.

Anthony

Now you have a 'trained eye' to spot the problems.

Every vehicle with solder joints has these issues eventually, not just Volvo branded relays.

When soldering remember to heat the pin that goes thru the board, not just wet the pool. Indicator of top job heat wise is a shiny pool.

JELG

Yep. Lucas electrics in Jags etc. give plenty of trouble too. Capacitors through the early 90's seem to be failing industry wide. They leak and go bad. I replaced several in a 940 speedo, unfortunately without lasting success. On most of the relays I have resoldered, it is the conection where the circuit board attaches to the pins that seem to have the issues. The rest of the solder joints usually look fine.

The point is, they can often be fixed with very little money spent. Just a bit of time and patience. And the stero microscope is almost a must.

I was surprised how well the photos came out. I'm glad people like them and find them helpful.

jamesinc

I've moved this thread from RWD to the Articles & Guides category

Laurie

Well, this thread made search for the "maybe useful electrical junk box" Surprisingly I found nine relays, mostly used for fuel injection system and some that came from behind the or steering wheel which I called "la-la" land and other unknown areas behind the dash.

Fixing the relays took less time than finding them and the soldering gear. All had poor quality soldering which seems to be the result of the component wires not being properly cleaned prior to assembly. The solder only covered the joint in part as the soldered had not flowed around the wire letting moisture in over time, ultimately oxidising the joint, rendering the relay useless.

Scraped the dodgy wire area to be re soldered with a scalpel making sure that the area was shiny clean. Also a small hole was drilled through the old solder in the board to clean things out.

All joints were re soldered. All the repaired relays work. Now for the big challenge to repair the last relay as in the photo. Might chuck it back in the box for buggered bits tho!

Now after a few hours work I have a small stock of relays worth a few hundred bucks.

The main thing is that I won't have to tramp all over town or wait for replacement parts to be delivered if they are available.

Don't toss out the dodgy relays, fix em.

Fun for a wet day???

JELG

Very cool. But I think the above relay might be a bit past it. It might be a worthy challenge though.

carnut1100

240 fuel pump relays... done this on basically every 240 i ever owned.

Laurie

Last year I happened to get a 240 that had covered only 46k, basically it is like a new car. However, after a few months the 240 would start after about for to five goes. My crook fingers got very sore twisting the key. The problem was the fuel pump relay.

I remembered through the mists of time the same thing happened within months of purchasing a new 1978 245. The problem was grotty solder joints in the fuel pump and fuses. This often happened when we spent a few weeks at our then holiday house which is on the beach front. The salt air would soon find a way into everything including relays. Also I had to twiddle the fuses on many occasions to get a circuit. To fix the relay problem after re-soldering the thing, I sealed the case and around the pins with a thin layer of silicone and still do. Never had another problem with that relay. Yep, the relay in the "new" 240 had been attacked by salt air even though the car is kept in a garage under a good car cover. It was evident by the greenish tint on parts of the copper un slodered wire as the colour of one or two solder joints were recently corroded in the relay. Some of the fuses were cleaned as they were beginning to corrode in the holders. I recon the headlights are now brighter too!!

i would rather have a go to fix old cars rather than walk away from these new computer controlled cars which most of us have no hope of fixing when they go bung.