Carb Fan Relay Eagle Eye help (1 Viewer)

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Hi all, so here is what I have. I have a good functioning carb fan, a new spal thermosensor and a new round relay.

1) When all connected, and when I attach the battery cables the fan turns on and just runs...and runs and runs.
2) with battery connected and carb fan disconnected, the round relay is hot. not good.
3) I suspect that perhaps the circuit board relay is bad somewhere.

Would someone with a keen eye take a look at the photos and tell me if you see anything that would indicate some failure on this part (outside of the ability to test individual components). I'm not an electrics guy; the solder points look solid, but there is some gunk on there which might be interfering. If it's a matter of just cleaning it, great. if not, I may go the InPower relay route and ditch the two stock relays.

Anyway, as always, any observations are appreciated.

20200708_130628_HDR.jpg


20200708_130701_HDR.jpg
 
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Is the Spal thermo-sensor a snap switch or just a variable thermo sensor? This application requires a true on/off snap switch
 

777Gage

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I've got three 40 relay's (for a 12/78) sitting on my work bench. Trouble shooting some similar issues
Relay 1. Turns the fan on when the key is turned off, but then doesn't turn off after 20-30 min...just keeps running, have to disconnect it
Relay 2. Completely dead - nothing
Relay 3. My stock one turns on sometimes (jiggle the connection) and it runs great - maybe the green female plug end needs re-solder on board?

Got another coming in the mail next week, will update if I solve anything
 
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I guess I need to look inside my relay, not quite sure where to ground the wire. Tried once on a header bolt, nothing. Is there a better place to ground that thermo switch wire?
 

spotcruiser

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Has anyone pointed out the broken solder joints under the plug connector? This is the most common damage area on pc boards with connection plugs.

I circled the pins that I believe have damage, but there may be (probably are) others. The large one isn't a stock solder joint and was probably repaired earlier. Certainly, all of the solder joints of the connector need to be looked at very carefully.

Inkedcarb relay_LI.jpg
 
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So essentially those tiny little cracks? Have to do a little research on fixing those. Thanks!
 
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well, I re-soldered the plug terminals to no avail. Still have the same issues as before. I think I'm going to go the Inpower timed relay route, and delete the two stock relays.
 
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Apparently the I.C. is the hidden function because it is a black square. I am a troubleshooter , so, if I want to restore something I tend to do so. What will happen is if you change to a "new" setup, it will work for sure but down the line someone will may have issues with the "new" system. And, for sure , that is why this thread exists. So many changes from stock have been done that we are detectives.

I guess I am a purist.
 

Eyedaho

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Hi all, so here is what I have. I have a good functioning carb fan, a new spal thermosensor and a new round relay.

1) When all connected, and when I attach the battery cables the fan turns on and just runs...and runs and runs.
2) with battery connected and carb fan disconnected, the round relay is hot. not good.
3) I suspect that perhaps the circuit board relay is bad somewhere.

Would someone with a keen eye take a look at the photos and tell me if you see anything that would indicate some failure on this part (outside of the ability to test individual components). I'm not an electrics guy; the solder points look solid, but there is some gunk on there which might be interfering. If it's a matter of just cleaning it, great. if not, I may go the InPower relay route and ditch the two stock relays.

Anyway, as always, any observations are appreciated.

View attachment 2365343

View attachment 2365344
Just a guess since I'm not familiar with that board, but if that transistor right below the jack is being used to turn on power to the fan, I would check to see if it has failed. Those can short closed as a failure mode, which could leave your fan running continuously rather than it being controlled by the temp sensor and timer circuit. It it has failed, you can probably look up the number on the side and order replacements from Mouser or Digikey for really cheap.
 
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I will look into that. I'm not an electronics expert so I dont know what the function of the various components are. When you mention the transistor, which component specifically are you referring to as there are several just below the plug?

Thanks!
 

Eyedaho

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I will look into that. I'm not an electronics expert so I dont know what the function of the various components are. When you mention the transistor, which component specifically are you referring to as there are several just below the plug?

Thanks!
Screenshot_20200711-124844.png


This guy here. It has the heatsink built in, so probably used for power switching (on/off). It has three legs (wires) with one being power in, one being power out, and one being a signal to turn the "switch" on and off. They're often pretty easy to test with a multi meter. If you give me the number on the side of it or take a picture of the writing, I can try to look up which leg is which for that particular transistor so you can test it.
 

Eyedaho

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Here is a pic of the transistor.

View attachment 2369020
I'm not an electronics expert, and some of the old time stereo guys would be way better at this than I. However, I'm pretty sure you're looking at a 2SB605. Looking at it from the direction in your picture, pin 1 on the left should be the emitter, pin 2 in the center the collector, and pin 3 should be the base. You can try measuring resistance between pin 1 and pin 2 (left and center) in both directions. With your probes connected one way you should have continuity and the other way should be open (no continuity). You can't always measure accurately with the transistor on the board, depending on how it's wired, but you can give it a try and see. There's also a Zener diode by the right hand leg of the transistor in your picture above. It's the one that looks like orange glass. The lead on that thing looks a little cooked too, and that might be a likely thing to fail also if the transistor failed. You can measure that the same way as the transistor. Should have continuity in one direction but not the other. Both of those components should be quite inexpensive. The 2SB605 looks like it's a really old part number, but I see them on Ebay for ~$5. I'm sure someone smarter than I would also know a modern equivalent. Here's a data sheet for the 2SB605 transistor:
 
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Ok, I checked both the diode and the transistor; getting correct continuity from both.
 

Eyedaho

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Ok, I checked both the diode and the transistor; getting correct continuity from both.
Open in one direction and closed in the other? Then I'm not sure, haha. You can check the other diodes in the board the same way. The electolitic capacitors (black cylindrical ones) fail, but they usually bulge on top and yours look ok visually. Resistors don't fail very often, and neither do the ceramic capacitors (round thin ones). There are some other smaller transistors that you can look up the pinout for and check the same way. And there's that timer chip that someone else mentioned.
 

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