Defender heater

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
J

JCP123

Member
Posts
46
I know that Defender heaters are never great however, mine is particularly bad and I wonder if I’m missing something obvious.

The engine gets up to temperature and the thermostat is functioning fine along with the water pump. All pipes are too hot to touch but the heater blows lukewarm at best and when I stop at lights for maybe a minute it blows ice cold until I start driving again. The heater has been opened up and new seals fitted because it was obviously crap, but it’s not made much difference.

Hot water is flowing through the matrix and the fan blows well. Are Defender heaters just this bad??
 
The plain answer is no, in good order in the UK they work well enough. What type/year is yours.
Issues. Old matrix can get clogged, there may be some flow but not enough. The seal between the heater unit and cab may be crap, often the case when cold air getting into cab. Heater pipes themselves may be clogging up.
 
it has a nut and bolt rebuild. The heater matrix is clean and in good condition. All the seals have been replaced in the heater box and to the cab. They were completely goosed too so I assumed that this would be the solution, but no. Nothing is clogged and the heater pipe leaving the matrix is very hot so it’s circulating, just not ‘exchanging’ for some reason. It’s not a complicated system by any means, hence my question.
 
Mine was crap too, I thought it was OK and all Defenders heaters are poor and my mate bought a new (to him) n96 300tdi D90 and it was like sitting in a oven after 15 mins ...

So I took mine out (not as easy as it is to type) and dismantled it ... painted it .... new matrix ... resealed it, just like you've done by the sound of it. I also cleaned out and sealed the plenum and now my heater is a lot better. More hot air in the cabin thats for sure ...

One of the improvements was to replace the resistor with a lower value one so that on 'low speed' it was around 30% faster.
It's better but still not as good as my mates, which defies logic.
 
sounds like I have a ghost in the machine! I haven’t changed the resistor because the fan blows just fine to be fair. It just blows cold air! I reved the knackers off it the other day to see how much black smoke it was emitting and the heater warmed right up. Engine temp didn’t change but the heater did. After about 5 minutes though it was blowing cold again.
 
I had an unknown stat in it to start with and the temp gauge was showing at 3/4 which I assumed was a faulty stat so I changed it for a genuine one. Gauge still showed the same so I put it down to a quirk. About 2 or three months later it just dropped to just under half way and has not changed since. It has been suggested that it was an air lock but I wasn’t. Either way, the heater has always been the same. So, while it does look stat related I can’t see how it is.
 
JCP123 said:
I had an unknown stat in it to start with and the temp gauge was showing at 3/4 which I assumed was a faulty stat so I changed it for a genuine one. Gauge still showed the same so I put it down to a quirk. About 2 or three months later it just dropped to just under half way and has not changed since. It has been suggested that it was an air lock but I wasn’t. Either way, the heater has always been the same. So, while it does look stat related I can’t see how it is.
Click to expand...
Well you revving the engine which makes the heater blow hotter would suggest to me the stat is partially stuck open.
 
I read that they were all bad. I then changed the thermostat in the engine and the heat coming out of the duct holes is at the "hotness" where you can hold your hand under it, but any hotter, and you would not want to.

As the OP notes, however, they're simple things -

The curious point for me is this -


when I stop at lights for maybe a minute it blows ice cold until I start driving again.

Basically that, pretty much, settles it -

Lack of flow, for whatever reason. Possibly combined with too low water temp, but if the engine is hot and the heater was hot, but goes cold, that's got to be a flow issue.


Edit - I assume the dash gauge doesn't suddenly go cold also?
 
The gauge stays constant at just under half regardless. The matrix has been flushed but i think I’m going to do it again.
 
Last year the original stat in my 200 gave up. I had two OEM replacements, one did not work at all and the other packed up after a month [stuck open] Found a new old stock original "Waxstat" been fine since.
 
Oh really? I’ll bear that in mind! Thanks very much. I just assumed that an OEM one would be ok. Well, at least more reliable than an aftermarket one anyway.
 
You must log in or register to reply here.

Similar threads

F
Thermostat
Replies
10
Views
606
tottot
tottot
Lej
Diesel heater + existing ducts
Replies
0
Views
640
Lej
Lej
G
Series three heater matrix blowing cold
Replies
11
Views
1K
Citizen Kane
C
T
200tdi defender heater bypass
Replies
2
Views
582
t.g0r
T
R
L322 60 reg TDV8 heater problems
Replies
16
Views
1K
Mark Piercy
Mark Piercy
Back
Top