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After measuring and testing all the continuity which seems fine -
1. They beep on 4 speeds and none on 0 (console)
2. Measured continuity between console plug and control resistor and beeps (each colour cable matched)
3. Fuse STILL works (just making sure)
4. When I measure the voltage between the motor cables (connected black probe on brown and red on red/black) I get a jolt of 1.3v and then 0 (on speed 4)

Apparently the circuit closes, but the voltage is not provided, nor kept to the motor.

How do I make sure the damned control resistor is actually good?

The 4 speed rotary is a purely mechanical switch that merely routes the incoming +12V to the respective resistor or direct in the case of Max speed.

When the resistor fuse fails, the fan will still run when speed 4 is selected. If the fan is not working at any speed, the problem is likely to be elsewhere.

I think it's one of the relays and now I'm trying to figure out which is which (under the dash). I narrowed it down to that as I get a small current on ignition and then it disappears. By apply V+ on fuse 33 blower works. I figured it it to be the relay. That is my line of thought.

Can anyone provide a relay diagram for this fraying pan, please?

Thanks!

Caddy Maxi 2012 1.6

Hi,

MY 2018 Mk4 - From 2015 ...

The output side of fuse SC33 is a black wire.
This morphs into a Red/White wire to feed the heater fan control switch.

Fuse SC33 is fed from the X-Contact Relief Relay on my Mk4 2018

In my fuse board X-Relay is top right - Light Green Relay marked 644

If this relay were faulty an awful lot of things would not be working !!!

If you are not getting 12V into fuse SC33 then that could be the issue - it should be on a common bus bar for fuses 28-33

Fuses SC 28-33 are all X Relief Relay fed fuses - Feed is via Fuse SC32 (from my reading of the wiring diagrams !)
Your Caddy may well be different !!!

petrev wrote: ↑Mon Apr 17, 2023 7:27 pm Hi,

MY 2018 Mk4 - From 2015 ...

The output side of fuse SC33 is a black wire.
This morphs into a Red/White wire to feed the heater fan control switch.

Fuse SC33 is fed from the X-Contact Relief Relay on my Mk4 2018

In my fuse board X-Relay is top right - Light Green Relay marked 644

If this relay were faulty an awful lot of things would not be working !!!

If you are not getting 12V into fuse SC33 then that could be the issue - it should be on a common bus bar for fuses 28-33

Fuses SC 28-33 are all X Relief Relay fed fuses - Feed is via Fuse SC32 (from my reading of the wiring diagrams !)

Fuse-Box-SC-1.02.jpg

Your Caddy may well be different !!!

I had a bit of hope with that relay being bad and now you turned everything on its head because it makes sense. Hey ho, no worries. I will try to find a 644 relay and test my theory first. I will try to test the 644 relay tomorrow as it got dark and cold and I am well annoyed with the thing..

If everything works if you put 12V on the heater fan control switch input wire (5-pin plug T5/5) you could always just run a new Ign. Switched live (4.0mm) and feed from a new fuse slot !?!

p.s. You have done 6+ posts now so you can post in the New Members Read This thread to get full forum access ...

I tested the 644 relay on 12v, it clicks and has continuity. The weirdest thing is that if I supply 12v on the relay, the blower works.

Where should I rund the wire to? Because it needs to power the controller to have different speeds... Right? Or am I missing something?

I am a total noob, sorry guys!

This is the relay box. If I remove relay 644 and measure on the motor the voltage is 0, if I put it back in, I get 1.2V and then it disappears. If I remove any other relays, I still get the small V on the motor side.



This is my fuse box. If I apply 12v on fuse 33. Everything works. The fuse is not blown. I checked/measured it.



I flipped the fuse box and the weirdest thing is that fuse 33 is on the ground and the blower starts working when I apply 12+ on it. What am I missing?!!?

I have no idea where to and from to jump an ignition wire so the blower will start

When you say fuse 33 is on ground, are you assuming the black wire is ground?
The black is the relief relay supply which is +12V when ignition is on but the starter is not cranking.
If you are getting 1.2V then this is likely a back feed from some module with more than one supply.

If your X contact relief relay is working correctly, these fuses will have a 12V supply.

Check the relay has 12V on the supply terminal and correct supply on the coil. If these are correct and there is no output, the relay must be faulty.

Doc wrote: ↑Tue Apr 18, 2023 11:11 am When you say fuse 33 is on ground, are you assuming the black wire is ground?
The black is the relief relay supply which is +12V when ignition is on but the starter is not cranking.
If you are getting 1.2V then this is likely a back feed from some module with more than one supply.

If your X contact relief relay is working correctly, these fuses will have a 12V supply.

Check the relay has 12V on the supply terminal and correct supply on the coil. If these are correct and there is no output, the relay must be faulty.

Relays are good. I just double checked them all.
Where should I plug a fused wire to bypass everything but the controller? This frying pan is getting on my nerves at this point. Taking it to an auto electrician will cost me a kidney for sure!

Hi,

What DOC said


Back of the fuse box ...

Black wire to the BUS Bar across fuses SC33 - 28 is the feed from X-Relay

This should have 0V IGN Off and +12V IGN On

Black wire out of SC33 is the feed to the Fan Control Switch - With the Fuse in place it should have +12V when IGN On.

If you are putting +12V directly to the BUS Bar and everything works then the issue is before the fuse box.
X-Relay, feed from X-Relay to Fuse Box, or the feed to X-Relay
Pulling the X-Relay there should be constant +12V on the top pin (#3) INPUT
Bottom Pin (#5) is OUTPUT to the fuse box
Putting 12V (40A supply !) to this pin is what should make the Fan circuit work ...

(green relay 644) Putting 12v on the bottom pin powers the fan.
There is continuity from the bottom pin to the black bar ( which means the problem is not from there)

Everything works with the green relay in apart from the blower.

It's a head scratcher and this is what confuses me! I have continuity on literally everything from the relay all the way down to the blower but measuring it only gives me a jolt of 1v on ignition then 0 with ignition on

PS: I have 12v on that relay so there should be no issues from the battery to it

Relay Out - If you connect Top to Bottom BIG pins does the fan run OK ?

This is what the relay should be doing if it is working properly !

petrev wrote: ↑Tue Apr 18, 2023 12:00 pm Relay Out - If you connect Top to Bottom BIG pins does the fan run OK ?

This is what the relay should be doing if it is working properly !

Connecting the big pins makes the fan blow! So... It's the relay?!