Caddy Maxi 1.6 heater blower not working

[Odo13tz]

I was right. The small V drops and doesn't keep the relay bridged. I took the cover off the new relay I got and noticed it. There is a thin brown wire as a red/light green on the back of it.

Made a short video but I don't know if I'm allowed to post a link to it

https://youtube.com/shorts/zFF8LBElQ5E?feature=share

I will try to get a ground on the brown tomorrow. It got too cold and dark now to be outside

[petrev]

Yeah, that's not good !

Pure Brown is the Earth (thin wire)

Grey/Red is the switched live signal (thin wire)

At least in my Mk4

[Odo13tz]

What would be the next step?
1. Try to get a ground and stick it in with the brown?
2.Anything that I should do with the red/green?
3. Any idea whee those thin wires are coming from and why are they not keeping V?

I'm trying to get an attack plan for tomorrow because my annual leave is finished and I have to go back to work

[petrev]

If you haven't got a test probe with a crock clip and a pointy probe then I would take my meter probe and ground the plug end to a solid chassis earth point and then stick the probe into the back of the relay socket brown wire and see if the relay closes and the fan works.

If it doesn't then I would connect to Batt+ at the plug end and stick the probe into the Grey/Red pin socket and see if that worked.



3. Brown should go to a chassis earth point

Grey/Red should go to the Onboard Supply Control Unit T52b/28 (think that's BCM)

[stu_b]

I am in Braintree (Colchester) but will ing to travel if it's not too far it's cold outside and I have no heating


WoW
I used to live not too far from there when I was a kid
Now I live in Australia

[Odo13tz]

Alright! I think I have isolated the issue.

The grey with red stripe thin wire that goes to the BCM does not get enough power to the relay to keep it in the ON position. This might be a problem from the BCM, which is a can of worms that I am not willing to open.

My question is: can I safely bridge the V+ to another relay? (The one next to it) I did that for a second and everything seems to work perfectly, but I don't know how safe is it to do that

[Doc]

Have you tried disconnecting the battery and reconnecting after a few minutes. Those BCMs can have a wobble sometimes and a hard reset solves it.

[Odo13tz]

In all fairness, I haven't tried disconnecting the battery but I jumped a small lead to the next relay and fixed the issue. Next time I fiddle with the battery I will remove the jumper and see if it works.

@Doc and @petrev Thank you so much for your help. You guys are a fountain of knowledge! Hat off to you guys!

[Odo13tz]

Caddy 2012 1.6 heater blower not working small write-up:

1. Check the blower motor to see if it actually spins, if it does keep reading, if it doesn't...do'h, change the motor
2. Check the green resistor pack and see if it works (it should only on speed 4 if it's a bad one) if it works on all speeds keep reading
3. See if you the wires from the green resistor pack to the central console have continuity, if they do, you're good, keep reading
4. Check the fuses (33 under steering wheel) if it's good, keep reading
5. Take the panel under the steering wheel out, on top of the fuse box there is a relay box
6. Check relay 644. If it's good keep reading
7. No the tricky part come into play:
- bridge the 2 BIG prongs of the relay (blower works?)
- check the thin wires from the relay (broun and grey/red stripe)
- brown thin wire at the back is ground, thin grey/red goes to BCM
- measure voltage, there should be 12V on those small wires. If it just gives you a jolt and then nothing... There's the problem. Either bad ground or bad positive (my issue was the positive not getting constant V and the relay opened)
- take positive from battery and stick it in the back with the grey/red. Works? Bad positive. Doesn't work? Keep reading
- take negative from the body and stick it with the brown. Works? Bad ground. Doesn't? Keep reading
- Doc suggested to disconnect the battery for a hard reset of the BCM and it may fix the issue.

If you're unlucky enough and nothing works it may well start praying and finding quotes from a professional because here is where my problem was fixed and I haven't dug further. Good luck!

Thanks @Doc and @petrev for their knowledge which helped me isolate my issue. I hope this write-up helpes someone!

[petrev]

Personally I wouldn't use the next door signal to close the relay as it is a BCM signal as well, and it is something to do with the starter circuit !?

I would do DOCs suggestion before any permanent-temporary fix/bodge just to make sure it can't be corrected simply.

Temporary Fix -
As the X-Relay is just to switch off larger drain items during starting and the fan/heater seems to be your only thing on this path, I (personally) would pull the X-Relay and fit a jumper - short loop 4mm² wire with big spade crimps on each end - between the 2 big terminal sockets. This is what the relay does when it is closed.
You should switch off the fan when starting your Caddy if you want to mimic the X-Relay.

And when Start/Stop is doing it's thing ...
.

[S.peck01]

Sorry to jump on your post
I’m having an issue where I have 12v to the grey / red when the relay isn’t plugged in but when it is there’s nothing.
Everything works fine when I jump 12v to it with the relay in though
I’m at a loss!

[johanson94]

hi
i have heater blower problem too
i have change the blower motor and the heater resistor the green ugly thing
i have power coming to the blower but nothing ive checked fuses etc
i have power from the switchs etc still nothing any ideas please
my vehicle is a caddy 1.6 diesel 2013 britsh gas van maxi

[STP]

Then maybe you have a broken earth connection to the motor or the blower switch. Do you get 12v when testing straight across the motor terminals, not just between one wire and a metal body bolt for example.

[johanson94]

Then maybe you have a broken earth connection to the motor or the blower switch. Do you get 12v when testing straight across the motor terminals, not just between one wire and a metal body bolt for example.

hi
i have got 12v going to plug of the heater blower but still don,t work basically ive checked everything what about the relay where can i find that
thanks

[STP]

No idea mate, (never had to find mine) but it wouldn't matter, if you have 12v to the motor plug then it should be spinning. You can connect a 12v battery charger to the motor to test it on the bench, that's how I test them.

To prove the supply to the motor you are better using a 21W brake light bulb and holder so it can draw current, as there may be voltage there but a resistance upstream means not enough current to spin the motor, it needs to draw about 7A to start and settles to 3-5A when running. If the lamp is dim, you have a problem further back with a bad connection or resistance somewhere. If it's bright, it should be working for the motor.

A digital test meter won't show that issue up. I do this for a living.