1990 Terrano heater issue

[crowy]

Hi all.First time poster here

I have a 1990 WD21 Terrano 2.7TD with a heater that does not work.Supply/return hoses are connected.A/C works fine.Blower motor works fine.I'm wondering if the temp control sliding switch is electrical or mechanical?Mine slides back and forth with hardly any resistance except for a very slight ratcheting as you move it.If that's normal then I assume ut's electrically operated.If it's not,then I think a rod/cable has come adrift.

Any ideas?Thanks in advance.

[RedPath88]

Welcome to NPORA

 

 

 

It should be mechanical, my 88's also has very little resistance but if you move it somewhat quick then you can hear the HVAC door close at each extreme. If that a try and if you hear nothing then it may very well be possible that the cable has come disconnected for one reason or another.

[crowy]

Wow !!Thanks for the quick response!!Ok.What I have found is if I put the Blower motor switch in the autu position and slide the temp switch acroo I can hear what sounds like a relay switching in and out .I dont hear anything like a door opening or closing like when switching between air vent outlets.

Edited May 4, 2015 by crowy

[RedPath88]

If your hearing a relay then perhaps it is electric... which of the following does your controls look like?

 

 

 

or

 

 

 

 

Mine are like similar to the first and fully cable operated. But in looking for those pics (web search) the second one came up as a 1990, I thought the change happened in 91/92.

But if that is what you have then they may in fact be electric/vacuum. Someone with more knowledge of that style will post I am sure. Since I have not had that style myself, I wonder if the actual mechanisms that move the doors electric or vacuum.

[crowy]

Yeah mines number 2

[RedPath88]

Ok in reviewing the FSM the system appears to be electric motor based. It appears that both the Auto and Manual may have been available, even in '94.

 

Until someone else can chime in with advice, page HA-55 of the 1994 FSM (See the pinned topic in "The Garage" section if you need to download it) has a trouble shooting procedures for the Auto System.

[crowy]

Feeling the radiator hoses and comparing the temps compared to the heater hoses tells me there is no water flow through the heater box.

Any Ideas?It's bloody cold here in winter!!!

 

Thanks Redpath.Tested as much as I could.All controls on the heater A/C panel appear ok

Edited May 5, 2015 by crowy

[crowy]

Now I'm thinking blocked heater core?

About to check it out

[crowy]

Heater core isn't blocked.The heater hose inlet next to the thermostat housing doesn't appeaer to have much flow.More like a trickle.Doesn't alter when switching from hot to cold on the sliding switch.Bothe heater hoses are near cold where they penetrate through the firewall.Seems like it may be an electrical fault There are 3 lots of wiring going to the housing that the thermostat attaches too.The wires going to the connection closest to the front of the vehicle sits right under the heater inlet.I'm wondering if this is just a sensor or some sort of electronic valve that opens and closes to let the water pass?Does anyone have an idea? :blink:

 

[crowy]

After running the car to operating temp,inlet heater hose is hot.Return hose is cold.So coolant is not passing throught the heater core.but when I disconnect hoses and hook up a garden hose water passes through core.GRRR!!So there must be a valve on the heater box that opens and closes to let the coolant flow though.

[RedPath88]

Wow no one has jumped into this thread yet?

 

 

 

 

I could be wrong but even if there is a valve causing your problems, then there should be no flow with the garden hose either if something is blocking inside the cabin. Where are you hooking up the garden hose? Are you passing the fresh water directly into the heater core inlet/outlet or are you connecting it to the heater hose or hoses?

 

Have you verified that the hoses are good? People have reported hoses having separated on the inside and caused blockage, even intermittent at times. Replacing the hose fixed the problem. Just saying that you might want to eliminate the hoses from the possible list of problems before digging into the dash.

[crowy]

Hi Redpath.I connected the garden hose to the heater hoses at the engine not the firewall so hoses are good.(All hoses and radiator were replaced 14 months ago.Have the receipt from previous owner.I have had the vehicle about 4 months and other than the heater issue I love it.I replaced the auto hubs with manual locking hubs,now no more nasty engage disengage bangs Previous owner Also had Ironman shocks fitted just before I bought it I also had fitted a pair of 2 inch lift heavy duty King springs on the rear for when the trailer is loaded full of firewood,no more sagging!!Anyway back to the heater.I triede reversing the hoses at the firewall just as an experiment.A waste of 10 mins,made no difference.

 

Here is a youtube video of a yerrano heater matrix.Not sure if it's a WD21 or not though.If it is all I can see is the heater valve on mine is closed(at least partially anyway) which is why the garden hose still pushed the water through.

 

https://www.youtube.com/watch?v=o82tm9Ungmg

 

Cheers Mate.