car relay problem

[not-bono-ever]

my classic tank daily driver has a problem- the power windows dont work

Now if I remove the gubbins under the dash to access the power windows relay and press in its sides of the relay, the windows work. When I let go, they stop. The relay now has no cover, so I can see the guts and the coils- this is what I press.this is wahat seems to make the circut

I have a new relay( I think is correct) but when I fit this, there is nothing at all happening.

I know that relays sorta allow small current to operate big current things ( like power windows) or maybe that is the other way round. Anyway.. anyone with good auto electric knowledge advise on this anoying and frustrating problem ?

I have another relay on order from a specialist, so that will be fitted eventually to see if it works

 

[souljacker]

Does the new relay not work if you 'press in its sides'? I don't get what you did to the old relay

 

[not-bono-ever]

nope it doesnt.but as its a very old unipart one thas i was told would work, i am not 100% it is a good one.

i think i may be forcing the connection across when i press the relay but am concerned this may impact the window motors themselves

or i can rip the door panels off and stick a hand winder on them

 

[mauvais]

I know that relays sorta allow small current to operate big current things ( like power windows) or maybe that is the other way round.

I'm not an electrician and I've no idea what you're doing to your poor relay.

But relays don't do that exactly. They're a current-operated switch. You send the 'small current' through it, like a signal, and it activates the 'big current' circuit.

So I suppose it's possible that whatever you're doing is merely completing that circuit, in which case your window switch or its circuit is bolloxed.

Get a multimeter and start finding out.

 

[not-bono-ever]

Think i will have to. I can cope with mechanicals of any kind but lose it completley with electricals. your point bout small current activating big current circust rings true and I am aware that if I chuck on permanent big current by forcing the relay, it will likely cause downstream damage.

 

[mauvais]

It shouldn't cause any damage per se, you're basically just making the circuit like the relay would. At least, I guess that's what's happening. The exception to this is that when the windows are fully up/down, you might be applying current when the circuit would otherwise be broken by some cutout switch. I doubt it to be honest.

If I were you, first thing to do, I would get the multimeter and check the voltage across the window switch when the switch is pressed. That'll tell you whether the switch circuit has power.

What vehicle is it?

 

[not-bono-ever]

its a volvo 240 slab saloon....

 

[mauvais]

Another hands-off option would be to get the wiring diagrams, check if anything else runs off the window switch circuit's fuse and then check if that still works properly. But it's a pretty low tech car so I guess perhaps not.

 

[not-bono-ever]

low tech ^^^ thats why i own it !

will plough through the club sites and see if there is anything on there

 

[mauvais]

Here's one:

Power window failure - Volvo Forums - Volvo Enthusiasts Forum

 

[not-bono-ever]

cheers-looks these slabs do get window issues after a quarter of a century......will have to master a multimeter when i get back from my trip

eta - there are only 250 of this model left on the road in the uk. wowz

 

[not-bono-ever]

solved

the car has ceramic fuses if you know what these are, but they had been replaced over the years by plastic ones and apparently these are rubbish/ get hot and get pliable/distort when hot. so when load goes through the, they can fail on an intermittent basis. It would seem that when I was holding the relay, it must have been doing some magic juju to the load and everything worked, when not, the fuses was failing.

fuse replaced with a ceramic one and the whole thing works again. I cant get my head around car electrics...