Go Back   The 75 and ZT Owners Club Forums > The 75 and ZT Owners Club Forums > The 75 and ZT Owners Club General Forum
Register FAQ Image Gallery Members List Calendar Mark Forums Read
Notices

Reply
 
Thread Tools Display Modes
Old 30th March 2022, 20:22   #1
Number 6
This is my second home
 
Rover 75 tourer Club CD/Limo Tints

Join Date: Nov 2008
Location: Meneac
Posts: 6,759
Thanks: 5,007
Thanked 1,609 Times in 869 Posts
Default Well here is a strange happening.Car Heater

The heater in the car (75 Diesel), has all of a sudden started to play silly luggers,, From cold with the temp set at 20 both sides the hot air starts to increase as the engine temp rises. All good, but after 20/30 miles at a sustained speed cold air starts to blow thru the vents, turn the temp up and you get warm air. There are no sign of over heating. The pipes to the heater matrix are both hot when the cold air starts to come thru the vents

Any one have any suggestions??
__________________
]

"I started out with nothing, and Ive still got most of it left!"
Number 6 is offline   Reply With Quote
Old 30th March 2022, 21:18   #2
MarkS
Gets stuck in
 
Rover 75 Diesel Tourer, called Perseverance

Join Date: Nov 2011
Location: Bournemouth
Posts: 664
Thanks: 189
Thanked 157 Times in 108 Posts
Smile

Check coolant level.
Have you done the top thermostat mod ?

Last edited by MarkS; 30th March 2022 at 21:24..
MarkS is offline   Reply With Quote
Old 30th March 2022, 21:36   #3
Number 6
This is my second home
 
Rover 75 tourer Club CD/Limo Tints

Join Date: Nov 2008
Location: Meneac
Posts: 6,759
Thanks: 5,007
Thanked 1,609 Times in 869 Posts
Default

Quote:
Originally Posted by MarkS View Post
Check coolant level.
Have you done the top thermostat mod ?
I have done the top thermostat Mod.

But this was done some time ago, the level of water never changes And this has only recently started to do this.

Oh and it has been bled correctly
__________________
]

"I started out with nothing, and Ive still got most of it left!"
Number 6 is offline   Reply With Quote
Old 31st March 2022, 00:31   #4
clf
This is my second home
 
clf's Avatar
 
MG ZT CDTi

Join Date: Jan 2014
Location: carrick
Posts: 7,859
Thanks: 3,494
Thanked 2,657 Times in 1,973 Posts
Default

Quote:
Originally Posted by Number 6 View Post
The heater in the car (75 Diesel), has all of a sudden started to play silly luggers,, From cold with the temp set at 20 both sides the hot air starts to increase as the engine temp rises. All good, but after 20/30 miles at a sustained speed cold air starts to blow thru the vents, turn the temp up and you get warm air. There are no sign of over heating. The pipes to the heater matrix are both hot when the cold air starts to come thru the vents

Any one have any suggestions??
switch off the auto mode, and switch to recirc (there is a combination of settings similar to this, but I can never recall it).

Mine does this, but it is limited to the upper drivers side air vents. Feet, and passenger sides remain warm. I have read this is a normal safety function to keep the driver alert.

If all of the vents turn to cold, then I would suggest an issue with the vent mixer flaps, or an issue with the air sampling inlet vent.
__________________


It is not gloss primer .............. it is duct tape silver!
clf is offline   Reply With Quote
Old 31st March 2022, 02:18   #5
MarkS
Gets stuck in
 
Rover 75 Diesel Tourer, called Perseverance

Join Date: Nov 2011
Location: Bournemouth
Posts: 664
Thanks: 189
Thanked 157 Times in 108 Posts
Smile

Underneath the clock is a vent control.

I believe this selects between (cold(er)) fresh external air, and (warmer) air to the driver side air vents.
( I expect somebody can clarify this).

If somebody has fiddled with it, it could explain the recent issue.

The environment controller is generally very very reliable. Unfortunately the cooling thermostats are known to be far less unreliable, with age, and may need replacing.

Last edited by MarkS; 31st March 2022 at 02:22..
MarkS is offline   Reply With Quote
Old 1st April 2022, 07:03   #6
SD1too
Doesn't do things by halves
 
SD1too's Avatar
 
Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model.

Join Date: Mar 2007
Location: Former Middlesex
Posts: 20,262
Thanks: 1,587
Thanked 3,749 Times in 3,181 Posts
Default

Quote:
Originally Posted by MarkS View Post
Underneath the clock is a vent control.
I believe this selects between (cold(er)) fresh external air, and (warmer) air to the driver side air vents.
( I expect somebody can clarify this).
That's basically correct Mark but it affects all the face level vents, not just those on the driver's side.
Quote:
Originally Posted by Number 6 View Post
... after 20/30 miles at a sustained speed cold air starts to blow thru the vents, turn the temp up and you get warm air.
John; that sounds like thermostat trouble to me, i.e. it is not compensating for the cooling effect of the increased air flow through the radiator when road speed is increased and sustained.

Simon
__________________
"Whatever is rightly done, however humble, is noble."
Sir Henry Royce.
SD1too is online now   Reply With Quote
Old 1st April 2022, 07:05   #7
dave lincs
Posted a thing or two
 
Rover 75 Saloon

Join Date: Mar 2014
Location: Louth
Posts: 1,394
Thanks: 380
Thanked 986 Times in 476 Posts
Default

When the vents blow cold what is the outside temperature as if warm outside then this is quite normal as the sunlight sensor on top of dash will see and put vents on slightly, is engine temperature gauge reading normal?
dave lincs is offline   Reply With Quote
Old 1st April 2022, 16:43   #8
Number 6
This is my second home
 
Rover 75 tourer Club CD/Limo Tints

Join Date: Nov 2008
Location: Meneac
Posts: 6,759
Thanks: 5,007
Thanked 1,609 Times in 869 Posts
Default

Quote:
Originally Posted by dave lincs View Post
When the vents blow cold what is the outside temperature as if warm outside then this is quite normal as the sunlight sensor on top of dash will see and put vents on slightly, is engine temperature gauge reading normal?
Thanks for the reply, The outside temp is anything between 1c and 10c when this is happening so not hot out side.

The temp gauge sits at half way and never moves, Always been there.
__________________
]

"I started out with nothing, and Ive still got most of it left!"
Number 6 is offline   Reply With Quote
Old 1st April 2022, 16:46   #9
Number 6
This is my second home
 
Rover 75 tourer Club CD/Limo Tints

Join Date: Nov 2008
Location: Meneac
Posts: 6,759
Thanks: 5,007
Thanked 1,609 Times in 869 Posts
Default

Quote:
Originally Posted by SD1too View Post
That's basically correct Mark but it affects all the face level vents, not just those on the driver's side.

John; that sounds like thermostat trouble to me, i.e. it is not compensating for the cooling effect of the increased air flow through the radiator when road speed is increased and sustained.

Simon
Well it had a new stat fitted a few years ago, and I left the old Renault 5 stat in situ.. but was told it would do no harm to leave it in place.
__________________
]

"I started out with nothing, and Ive still got most of it left!"
Number 6 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 11:15.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright © 2006-2023, The Rover 75 & MG ZT Owners Club Ltd