The heater fan don't
start. I can hear a click from a relay, when I turn the fan speed. It's dead for a couple of
days, and then it works again. What could be the problem ? A loose electric connection ?

you must check the resistor block near the fan
motor. there is a thermo-type fuse that can be rust and do not allow the fan to work.

Hey Guys,
I have an 86 GLT and have the same problem. I can hear the Relay Click but
unfortunately no fan. I have checked the fan and know that works. Im at the stage where I'm
thinking of re-wiring the whole fan. I also looked for the resistor block but couldnt find anything.
Any help that can help fix this would be greatly appreciated.

Depending on the year of your 300 there is a resistor either inside or outside the plastic fan housing. I have a 86 360 glt so mine was on the inside. Test it for continuity with a multimeter and see what happens. Chances are that it will be the resistor is stuffed (a common problem). Hope its of some help

Krish

I also have a fan problem and I'll post here.

The fan doesn't work at all.

The fan motor itself works when connected dirrectly to power source (battery), so it's probably OK.

There is voltage at the wire that connects to the fan motor.
There is good ground at the ground wire.

Both fan relays are OK.

When everything connected together the fan doesn't work.

What else should I check? I don't suspect the resistors because fan also doesn't work at full speed (which bypasses the resistors).

Car: 87 360 GL

Thanks for any suggestions.

Unfortunately the fan current still has to pass through the resistor pack, even at full speed it still has to pass through the thermal cut off.

The resistor pack is inside the fan housing itself, and involves taking out the heater box assembly and springing the clips apart (careful you don't lose any!)

The resistor coils are usually fine, its the thermal cut out that gives trouble. There is a little springy bit that is designed to bend away and cut the circuit if the resistor wire gets too hot to prevent a fire, but they always rust and bend out of shape. We 'adjusted' ours by cleaning it and bending it back until contacts touched each other.

Andy

I have a problem with the fan too. 3rd speed doesn't work. I've checked the fuse and the relay in the fuse box.
I've posted this problem somewhere else in this forum but I haven't found an answer yet. Is it the switch or maybe something else?
Winter is coming so help would be appreciated.

pettaw wrote:Unfortunately the fan current still has to pass through the resistor pack, even at full speed it still has to pass through the thermal cut off.

The resistor pack is inside the fan housing itself, and involves taking out the heater box assembly and springing the clips apart (careful you don't lose any!)

The resistor coils are usually fine, its the thermal cut out that gives trouble. There is a little springy bit that is designed to bend away and cut the circuit if the resistor wire gets too hot to prevent a fire, but they always rust and bend out of shape. We 'adjusted' ours by cleaning it and bending it back until contacts touched each other.

Andy

Thanks, I found the resistor pack. Everything is corroded / dirty / oxydized and I think the problem was that the thermal cutoff had poor contact and was heating up by itself and cut the circuit. I think I'll just replace the whole pack as it's in very poor condition. Any idea about the original part price? I'll ask the dealer tomorrow anyway.

Juha wrote:I have a problem with the fan too. 3rd speed doesn't work. I've checked the fuse and the relay in the fuse box.
I've posted this problem somewhere else in this forum but I haven't found an answer yet. Is it the switch or maybe something else?
Winter is coming so help would be appreciated.

There are 2 relays for the 3rd speed. On is at the fuse box (D location), another is near the steering column (it has 1 yellow wire, 2 red wires and 2 brown ones - yours may be different depending on the year).

Also, speeds 1&2 use the fuse no. 19, speed 3 uses fuse 12.

If you'll be replacing any relays, pay attention to the pin locations.

Hi Guys,
I have the same problem as well - on an 84 340DL. I left the car up for about 2 years and the fan does'nt work at all now. I can also hear the relay clicking and when I click the fan on to max speed, the engine revs drop. Where is the resistor /heater fan under the dash and am I as well replacing the entire unit with another one (possibly risky if it comes from a scrap yard?!)
Thanks,
Paul.

All the info is in this post.

pettaw wrote:Unfortunately the fan current still has to pass through the resistor pack, even at full speed it still has to pass through the thermal cut off.

The resistor pack is inside the fan housing itself, and involves taking out the heater box assembly and springing the clips apart (careful you don't lose any!)

The resistor coils are usually fine, its the thermal cut out that gives trouble. There is a little springy bit that is designed to bend away and cut the circuit if the resistor wire gets too hot to prevent a fire, but they always rust and bend out of shape. We 'adjusted' ours by cleaning it and bending it back until contacts touched each other.

Andy

360GL wrote:

Juha wrote:I have a problem with the fan too. 3rd speed doesn't work. I've checked the fuse and the relay in the fuse box.
I've posted this problem somewhere else in this forum but I haven't found an answer yet. Is it the switch or maybe something else?
Winter is coming so help would be appreciated.

There are 2 relays for the 3rd speed. On is at the fuse box (D location), another is near the steering column (it has 1 yellow wire, 2 red wires and 2 brown ones - yours may be different depending on the year).

Also, speeds 1&2 use the fuse no. 19, speed 3 uses fuse 12.

If you'll be replacing any relays, pay attention to the pin locations.

Thank you.
Man those relays are in a terrible place...

Just in case someone wants to know, the new resistor pack (for late models) costs 71 EUR at the dealer... a little expensive for 2 hairdryer springs!

Hi,

Same problem here. First time the problem was actually in the swithch. I just opened it, and cleaned. Then the fan worked again, in all positions. Now 1y later, nothing happens in any position, but just the relays.

Fan itself works, when powered directly from battery. So I just had enough, and made an extra connector (with fuseon wire) to get it work !

br,Kari

I changed both relays and the fuse. 3rd speed is still mute.
So it has to be the switch?