Heat Always On, Please Help (405 Mi16 1990)

[Guest faern]

Hi! this is my first post.

 

I have a problem that is kind of irritating now when the summer is closing in.

The ventilation is always blowing full heat

When I turn the engine on (it's cold) and have the fan speed set to zero no air comes out of the vent. But when the heat builds up in the engine more and more air is coming out. And when the engine is on full working temp (~80C) the vent is blowing with full power and full heat (really hot!) even if I have the fan speed set to zero (blows even more if I turn it on).

Turning the temp control makes no difference at all. I have checked that the control generate different resistance(ohm) when turned.

 

Some months ago I removed the black box behind the radio, I thought it had something with the alarm (that doesn't work) to do.

When this problem with the head started (I'm not 100% sure if it was at the same time as the removal of the box) I first didn't think about that box, but later when I followed the cables from the heat control I realized that they ended in a connector. So I searched for the box and read the text on it, it said thermal something, god I was embarrassed

I reattached the box and thought I would live happily ever after, but NAH! the box didn't fix the problem at all.

 

Has anyone had the same problem? My guess is that the box is either broken or something gets confused when it's reattached. Or maybe the engine that controls the cooling water flow is jammed at fully open.

 

Please help.

Best regards Linus.

[Borntobewild 1]

Welkom ;-) Hope these know-it-all 405 lovers got the awnser for you

[Feeble 0]

Mine's been like that since I bought it... Damn annoying with Summer coming up...

[TonyW 0]

That'll be the thermo control unit then, and its broken, just like mine!!!

 

I'm currently having a complete mare trying to get mine sorted and is doing exactly the same as yours, so if you find a way to sort it or somewhere to get a replacement then let me know!!! Its getting warm in my Mi when the sun is shining outside and the fan is cooking me!!!

[JOHN89MI16 0]

I know this probably doesnt help but mine is the same. It looks like its a common problem.

I did manage to get cold air to come through my vents once but i had a right knightmare getting hot through again so when i did finally get hot air again i decided to leave it on hot.

I just wind down the windows to let the air out or the best trick ive found is when your driving, open the sunroof and set the hot air to windscreen and most of the hot air goes out the sunroof due to hot air rising and all that while still keeping inside your car warm enough not to be uncomfortable.

I hope this helps alittle because i keep meaning to find out why this happens too but i just dont have the time.

[kutija1345402283 0]

Hi.

On phase 1 you have a broken cable or connection where cable goes onto that knob on instrument panel for regulating temperature.

So you need to dismount everything and change the cable or knob....

 

On phase2 ,at least on my T16, there is electromotor regulating hot-cold and small wheels inside tend to brake and it can be repaired replacing small plastic wheels inside from another used one or buy a new one which isn't cheap afair.... so don't know if this is the case on all phase 2 405s.

Anyone with a little knowledge should be able to repair this...

Edited April 17, 2007 by kutija

[Guest Oceansandmts]

If they are anything like the US version, either the servo (actually the plastic gears) is broken or the heater ECU box has failed. If it is the servo, you often hear a clicking sound under the dash from the stripped gears. The ECU is located under the radio, forward on top of the tunnel, accessed from the middle kick panels. The servo is more difficult in the US, requiring a small hole in the glove box and good dexterity, but with RHD maybe it is easier. Combining used ones can work if you can find a complete set of good plastic gears; of course a new one solves the problem, although they are expensive; I understand some Land Rovers use the same servo and the Land Rover part is less expensive.

 

You can just remove the servo and lock the lever on the air flap with a small screw, cool in the summer, changing to warm in the winter. Or you can remove the servo and install a cable to move the temperature air flap.

[Baz 421]

Is this not simply the little black electric box that controls a flap to differentiate hot/cold air, kind of as said?

 

You turn the knob on the facia, which iirc, works the metal rod that which then electrically works the hot/cold air function. Or similar anyway!

I still have a good working 'black box' that someone was after a while back...

Edited April 18, 2007 by BazGTMi

[Feeble 0]

Will that fix the problem then Baz? I'll take it as well as the boot seal, if the person who wanted it doesn't contact you!

[Guest faern]

Thanx for all the tips. I can't see why the electronic thermal box would break. I will try to remove the servo engine this weekend and see if it's jammed. If not I guess I need a new thermal box.

[TonyW 0]

You can just remove the servo and lock the lever on the air flap with a small screw, cool in the summer, changing to warm in the winter.  Or you can remove the servo and install a cable to move the temperature air flap.

<{POST_SNAPBACK}>

 

Have you got any pics or a proper detailed description of how to do this? My TCU has been removed for my electrician to find another one but i'm locked on bl**dy hot and if i could change it myself that'd be great, i'd just need an idea of what I was looking for before diving in with the screwdrivers!!!

 

"I understand some Land Rovers use the same servo and the Land Rover part is less expensive" Or maybe somebody knows what part number this is so i can have a look for a cheaper one

[Guest Oceansandmts]

In the US version the dash knob is a variable resistor which sets the temperature of the cabin. That temperature is sent to the ECU, along with the outside air temp and the current inside temp, and the ECU then controls the servo which moves the flap in the heater box to mix the correct amount of hot and cold air. The water flow through the heater is always full on, the temp is controlled only by the flap position,

 

The Land Rover servos are here: http://www.roverparts.com/Parts/STC3259G.cfm. I guess they are actually for a Range Rover, and you get to buy three at a time for not much more than the Peugeot price for one. These are in North America, but the web site at least tells you the model of Range Rover.

 

To shut the flap you need to remove the servo, it looks like the picture of the Range Rover part, on the US cars it is on the right side of the heater box, held to a small bracket by two screws, which in turn is held to the heater box by two small screws. It is difficult to remove in a LHD car, as the glove box will not come out, so you get one screw reaching up behind with a screwdriver bit on a small rachet and extension, and the other screw by drilling a small hole in the side of the glove box and using a long screwdriver through that hole. Having already done this three or four times, it has now become easier. I must be different for a RHD 405

 

I hope this helps, I am not sure how much applies to a RHD Phase II 405.

[TonyW 0]

Cheers for that, i think i might be brave and take the centre console apart next week when my parts CD arrives and I know what i'm looking for and have a go, it cant get any worse coz every trip is turning the Mi into a sweat pit at the moment!!!

[Feeble 0]

Does it not help just to shut the vents then? Mine gets warm with the windows up, but it's never unbearable!

 

Open the vents though, and it's a different matter entirely

[TonyW 0]

I shut the vents but some of the air comes up thru the screen vents, warming things a bit! I try to have the sunroof and the windows open as much as poss now!

[Guest badboyracer3500]

I shut the vents but some of the air comes up thru the screen vents, warming things a bit! I try to have the sunroof and the windows open as much as poss now!

<{POST_SNAPBACK}>

 

 

 

 

turn the direction control off screen and to vents that way with them shut you should find no air out through screen vents.

[Baz 421]

That little servo looks exactly like the box i was talking about i removed, only without the fly off connections. Holds on with 2 screws. sounds like we could be talking about the same thing then...

[petert1345402284 0]

The problem is the servo motor as described by Baz. It's on the right hand side of the heater matrix, high up in the foot well, drivers side (RH drive car). The issue is that the gears inside the black box strip and the motor can no longer return the flap to mix the desired temperature. The easy fix is to remove the box. Undo the two retaining screws and pull it off. You can then manually move the flap with your hand. You'll only have two positions however, full hot, or no hot air. You can't change the position whilst driving however, unless you are double jointed and have extremely long arms! I went for three years with my car like this. But then in Sydney, you rarely need a heater, just A/C. I'll take a picture so you know what I mean.

 

When ever you see a 405 being wrecked it's a good idea to always take the servo motor. I keep a couple spare at all times.

 

It's part H607 in the diagram. Note that it's only fitted to cars with "Climate Control". 405's which have plain jane A/C or no A/C, will not have the motor.

Edited April 20, 2007 by petert

[Guest faern]

I have to warn you. Don't just close the vent and pretend nothing happened!! I did and the compartment where the stereo (a dvd/mp3 player in my car) is mounted gets so hot that the stereo broke :S

Edited April 20, 2007 by faern

[TonyW 0]

Petert, thats just the info I was after! I'm gonna have a go, set it to cold for the summer months and then switch it over for the winter. I'm fed up messing around with auto electricians, nobody has a proper clue!

 

Just as part of that, how does the centre console come off so I can get into it? I know there is a screw at the top of it thats under a pop off cover, are there any others?

 

Faern :- Couldn't agree more, my stereo has been getting red hot recently so have the window blowers set to blow the hot air out of the open windows!

[Baz 421]

That's it! Just looked at my spare one, i was wrong it does have the fly off connector on it!

[petert1345402284 0]

Just as part of that, how does the centre console come off so I can get into it? I

<{POST_SNAPBACK}>

 

No need to take the centre console off. Assuming your car is RHD, lay upside down in the drivers footwell, feet out the door. You should be able to see it on the side of the heat matrix.

[TonyW 0]

I'll be giving that a go on my rest days next week, nice one

[Baz 421]

I don't remember it being too difficult to get to no, may be easier to remove the panel under the steering column but not a major hardship.

[Guest faern]

The servo is on the passenger side right? There is a black box with a cable to it there that I am trying to remove, but it's really hard to do. I can't reach the second screw. The first one I removed through the hole in the glove box. but the second is behind the glove box, it can be seen if you lie down on the floor and look up where the fan is located. But it's too narrow to remove, do you have any tips on how to remove it/what tools to use?