Cooling fan relay

[TNMGB]

Okay, so I finally figured out that the reason my '79 B has been running hotter than usual is that I haven't been hearing the fans kick in. A mechanic buddy of mine took a look and after a short time under the hood decided it was the relay; we actually found the info in the owners' manual useful and jumped the switch on the top of the radiator and on came the fans. After turning off the ignition, I later tapped the relay while the engine was running and again the fans sprang to life.
Now here's the question: which relay do I use to replace this? I'm not seeing anything in Moss Motors that looks to be what I need so I don't know if something is interchangable here. Can someone offer a part number?
Also, I see that it is mounted by a screw to the fender well but when I turn the relay housing, the screw doesn't seem to be turning in the wheel well. Is there a trick to this that doens't seem to be obvious?
Thanks!

 

[PAUL161]

I'm pretty sure that Tony would have the answer. tony@theautoist.com PJ

 

[Naomi]

I wouldn't thing it would be the "relay". The relay that feeds the cooling fan is the same one that feeds the ignition circuits and if it were bad the car would not start. What you need is just the switch that fits in the top of the radiator and Moss does have them. Give em a call and they will give you the number and price immediately and ship right out to you. They have both the OEM and aftermarket which both work the same. Price is a great difference though. It is a common item on Rubber Bumper Cars and I've bought several of them over the years /ubbthreads/images/graemlins/smile.gif

 

[TNMGB]

This is not the same relay as is the ignition because the only thing connected to it is the switch to the radiator. I did neglect to mention that even when I jumped the switch with the paper clip I still had to tap the relay to get the fans going.

 

[jlaird]

Ha, must be a raceing mod. Get a new relay and if only the fans are on it I would suggest that any relay 12V from your friendly autoparts house would work.

 

[TNMGB]

Thanks, Jack. I'll check around and see what I can find.

 

[Naomi]

And I agree with Jack By the way you must have three relays under the hood. My 79 has only two relays: one relay for the starter and one for the ignition which picks up all circuits that should be on when the key is on. Somebody was thinking to add one just for the fans /ubbthreads/images/graemlins/smile.gif

 

[TNMGB]

So how does this relay come off? I'm still a little bumfuzzled by this part...?

 

[Nunyas]

how are the connections on that relay? Are they clean? Are the leads connecting to it getting a good solid electrical contact? If tapping the relay causes it to energize, that leads me to believe that of the following things may be happening: 1) The contacts need cleaning both on the leads and on the relay, 2) the relay is sticking in the un-energized state and tapping it is enough to free the plunger, or 3) both are happening.

If you're adventurous, you could try taking the relay out and cleaning up its internals. However, that may prove to be less fun/rewarding than just getting a new one and replacing it. If you do get a new one, make sure you get one that can handle the current draw of the fans. The amp rating that you need should be on the side of the relay already in the car. It probably wouldn't hurt to use a relay that can handle more current, but I'd try to keep the "energized" power draw of the relay itself less than or equal to that of the original.

 

[TNMGB]

Yes, the contacts are frighteningly dirty/rusty on the relay itself and it may be easier to just replace it...but again, now how does it come out? If I could remove it, I'd give cleaning the contacts a good try.

 

[jlaird]

Must be some bolts or screws someplace.

 

[TNMGB]

Well, yeah...I stated earlier that I see the end of the screw through the wheel well but not the top of the screw on the relay itself...is there a plate that comes off and you then see the top of that mounting screw? /ubbthreads/images/graemlins/confused.gif

 

[jlaird]

So, cut the screw off and drill out whats left from the wrong end??

 

[TNMGB]

Thanks, Jack, but I did call my local MG mechanic and he said he's got probably got a relay and he'll pop it in there for me...yay!