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Testing junkyard relay finds

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uberwasser

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1979 & 1985 300D's
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Discussion starter · #1 ·
I went to the junk yard the other day and picked up a collection of relays, just for a rainy day. They were from a rather nice 1978 300D that was a sad sight in the yard :(

Anyway, I had a few questions about them. First of all, here is the short list:

Non-turbo glow plug relay - 001-545-22-32

Seat belt warning control relay - 001-545-52-32

Two multi-purpose relays - 001 542 02 19

All genuine parts.

So, that said, two main questions. First -

The multi-purpose relays came out of this box on the '78 (my car pictured)

Image


What would they each be for?

Second -

Is there any risk in simply swapping the junk yard relays in place of my current working relays temporarily to see if they are good? I want to check in case I need to return any. But, I also don't want a bad relay to damage anything, if that's even possible. Electrickery is not my strong suit :surrender:
 
#2 ·
Other than physically breaking something 'cos you tugged too hard I can't see how it would go wrong so long as you fit like with like.

Otherwise on the relay itself there is often a wiring diagram - you could test them out of the car too. In the situation where you see an earth symbol put that on the negative terminal of a battery (electrickery isn't my strong suit either but I reckon I got that right!)
 
#3 ·
Those multi-purpose relays have different functions depending on what car they go in. On my '84, in that same box, one relay switches on the A/C compressor, and the other one controls the auxiliary electric fan. The relays are identical.

One way to test would be to put the replace the relay that controls the A/C and then see if the compressor turns on with the temp set to MIN. If the compressor will not come on, the relay is bad. But you have to have a known working compressor for this test to be valid.
 
Discussion starter · #4 · (Edited)
Well I have your known working compressor but its sitting in my tool shed!

Pierre said mine wasn't totally seized but that my refrigerant was likely low enough to not allow it to kick on even if it could. Have to go over the system and fix any leaks. He was thinking it was the schrader valve in particular.

I think the purpose of the relays makes sense for my car too. I'm betting it is compressor and aux fan. Since those relays were dirt cheap with the two for one deal I got I'll just hang on to them. I'll see about testing the other two though, since they cost a bit more.
 
#6 ·
Iridium said:
Those multi-purpose relays have different functions depending on what car they go in. On my '84, in that same box, one relay switches on the A/C compressor, and the other one controls the auxiliary electric fan. The relays are identical.

One way to test would be to put the replace the relay that controls the A/C and then see if the compressor turns on with the temp set to MIN. If the compressor will not come on, the relay is bad. But you have to have a known working compressor for this test to be valid.
Click to expand...
Could you let me know were the A/C relay is located , thanks .
 
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Iridium
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