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

Reply
 
Thread Tools Display Modes
Old 18th July 2016, 20:28   #1
Alexander MOB
Newbie
 
Rover 75 Club CDT

Join Date: Dec 2015
Location: Coventry
Posts: 4
Thanks: 0
Thanked 0 Times in 0 Posts
Default Rover 75 air conditioning doesn't switch on

Hi All,

I have a Rover 75 Club diesel with a problem that I try to fix. I have to go on a road trip and the air conditioning is not working, the car transforms in a sauna and I have to drive with the windows down. It's horrible
;
First I went to fill the installation with gas but hasn't get any better. The guy from this service wasn't doing electronics but he knew a few things and was nice enough to guide me. So this is what I did:

- took the air con relay and checked it with a digital multi-meter
- I put 12v on the relay coil, it clicks very good and the contacts work perfect (checked the switch on/off with the multimeter's buzzer)
- went to the car and with the relay dismounted and the AC on I check the pins from the car side
- the coil pins don't have any signal but the contact/switch pins have 12 volts (for the compressor)
- I take a piece of wire and connect the switch pins. They make a small spark and I hear the compressor starting.

I live it like this for 10 minutes but the air still doesn't get cold... probably now I have to refill it (the guy said that if the compressor doesn't work he cannot refill it because he needs some pressure)

So the relay coil doesn't receive the signal to start the compressor?

What should the issue be now? On the air con pipes there is a temperature sensor with a switch that this guy said it could be broken. Is there a way to check it before buy it?

It could be something else? What do you guys think?

Cheers and regards,
Alexander
Alexander MOB is offline   Reply With Quote
Old 18th July 2016, 20:43   #2
T-Cut
This is my second home
 
Rover75 and Mreg Corsa.

Join Date: Nov 2006
Location: Sumweer onat mote o'dust (Sagin)
Posts: 21,751
Thanks: 341
Thanked 3,660 Times in 2,924 Posts
Default

Quote:
Originally Posted by Alexander MOB View Post

- took the air con relay and checked it with a digital multi-meter
Which/where is the relay tested?


Quote:
- I take a piece of wire and connect the switch pins. They make a small spark and I hear the compressor starting.

I leave it like this for 10 minutes but the air still doesn't get cold...
You haven't mentioned the radiator fan. Does that run when the compressor runs?

Quote:
On the air con pipes there is a temperature sensor with a switch that this guy said it could be broken. Is there a way to check it before buy it?
I suspect that's the trinary valve/pressure switch. It controls things according to system pressure.

Quote:
What do you guys think?
Find a qualified aircon specialist.
Check the operation of the slow speed fan by doing the Demist test.

Diagnosing the problem will be a simple matter of answering questions from people who'll be along shortly.

TC
T-Cut is offline   Reply With Quote
Old 18th July 2016, 21:25   #3
Alexander MOB
Newbie
 
Rover 75 Club CDT

Join Date: Dec 2015
Location: Coventry
Posts: 4
Thanks: 0
Thanked 0 Times in 0 Posts
Default

I posted some photos.

I checked the relay using a 15 volts laptop charger and following the diagram on its body. Its the black one on the photos.

I connected the 15V supply on the coil and in the same time I checked the contacts so see if they switch. Connected the multi-meter to the contact pins and the supply to the coil to see if I have contact and any resistance - its 0 ohm to both contacts so the contacts are clean

I will have to check the radiator fan then.

One of the photos is with this valve. It has 4 wires.

Don't know what this Demist test is. Its a normal diagnostic?
I could get one if its useful and will solve the problem.

To be honest I try to reduce costs... I already spent some money on tips with those advice and have a lot of things to fix to make this Rover decent. I will pay for any test if its needed but if its possible I can check things on my own (if its possible)

Regards

[IMG][/IMG]

[IMG][/IMG]

Alexander MOB is offline   Reply With Quote
Old 18th July 2016, 21:47   #4
HarryM1BYT
This is my second home
 
HarryM1BYT's Avatar
 
75 Contemporary SE Mk II 2004 Man. Sal. CDTi 135ps, FBH on red diesel, WinCE6 DD

Join Date: May 2010
Location: Leeds
Posts: 17,273
Thanks: 2,160
Thanked 2,061 Times in 1,586 Posts
Default

Quote:
Originally Posted by Alexander MOB View Post
That photo is of the 'trinary' switch. It determines if there is enough pressure or too much pressure in the system before allowing the compressor to run, or stopping it from running. Most likely the switch is fine, but the problem is wrong system pressure.
__________________
Harry

How To's and items I offer for free, or just to cover the cost of my expenses...

http://www.the75andztclub.co.uk/foru...40#post1764540

Fix a poor handbrake; DIY ABS diagnostic unit; Loan of the spanner needed to change the CDT belts; free OBD diagnostics +MAF; Correct Bosch MAF cheap; DVB-T install in an ex-hi-line system; DD install with a HK amp; FBH servicing.

I've taken a vow of poverty. To annoy me, send money.
HarryM1BYT is offline   Reply With Quote
Old 19th July 2016, 10:41   #5
T-Cut
This is my second home
 
Rover75 and Mreg Corsa.

Join Date: Nov 2006
Location: Sumweer onat mote o'dust (Sagin)
Posts: 21,751
Thanks: 341
Thanked 3,660 Times in 2,924 Posts
Default

Quote:
Originally Posted by Alexander MOB View Post
Don't know what this Demist test is.
Demist Test: https://cse.google.co.uk/cse?hl=en&c...=demist%20test

Report back with the result.
If the aircon system has no refrigerant or too much refrigerant, the fan may not run anyway, but do test and see.

TC
T-Cut is offline   Reply With Quote
Old 19th July 2016, 18:54   #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: 20,265
Thanks: 1,587
Thanked 3,749 Times in 3,181 Posts
Default

Quote:
Originally Posted by Alexander MOB View Post
I take a piece of wire and connect the switch pins. They make a small spark and I hear the compressor starting.

I live it like this for 10 minutes but the air still doesn't get cold... probably now I have to refill it (the guy said that if the compressor doesn't work he cannot refill it because he needs some pressure)
Alexander,

You should not force the compressor to engage if there is insufficient refrigerant gas in the system. You could damage it doing this.

As T-Cut has said, if the radiator fan does not run and the compressor does not engage when you press the windscreen demist button with the engine running, then you need to call out an air conditioning specialist.

Simon
__________________
"Whatever is rightly done, however humble, is noble."
Sir Henry Royce.
SD1too is offline   Reply With Quote
Old 19th July 2016, 19:56   #7
Alexander MOB
Newbie
 
Rover 75 Club CDT

Join Date: Dec 2015
Location: Coventry
Posts: 4
Thanks: 0
Thanked 0 Times in 0 Posts
Default

First of all, thank you for the all the reply's. I appreciate it.

I live in Coventry but I started searching for a specialist in Birmingham, maybe I find more options. Big garages want me to leave the car for 3-4 days but I cannot do that since I go to work every day. Even Kwik fit wants it for 2 days because they don't have the specialist there all day.

If you know any specialist that can take a look please let me know. I can even go further that Birmingham this saturday, and wait for a few hours there to fix it, is not a problem.

I assume the fan is the one in front of the radiator and yes, it doesn't work. I identified the relay, tested it and it works fine.

I pressed the demist button and the compressor or the ventilator still don't start. It just takes the Climatic sistem's fan to maximum and switches the flow of the air to the windscreen.

Posted two photos, one with the interface of the climatic system and one with the ventilator that I assume we are talking about (I can see it thru the bumper grill, the photo is from google)



Alexander MOB is offline   Reply With Quote
Old 19th July 2016, 20:59   #8
T-Cut
This is my second home
 
Rover75 and Mreg Corsa.

Join Date: Nov 2006
Location: Sumweer onat mote o'dust (Sagin)
Posts: 21,751
Thanks: 341
Thanked 3,660 Times in 2,924 Posts
Default

I suspect there are two problems. The aircon system needs a proper service/refill. The radiator fan slow speed and likely the medium speed has failed. I think your 2001 model will have a 3-speed fan (no resistor visible behind the fan blades?). If so, the motor brushes are the problem and with luck (50%) you might be able to replace hem. If not you'll need a new/replacement fan. It's advised to fit the later 2-speed with uprated resistor or fit an after-market alternative fan like the Revotec, etc.

If it's actually a later 2-speed that's been added, then a simple resistor swap is probably all it needs.

Trinary Test: http://www.the75andztclub.co.uk/foru...ad.php?t=35567

TC

Last edited by T-Cut; 19th July 2016 at 22:48..
T-Cut is offline   Reply With Quote
Old 15th August 2016, 11:41   #9
Alexander MOB
Newbie
 
Rover 75 Club CDT

Join Date: Dec 2015
Location: Coventry
Posts: 4
Thanks: 0
Thanked 0 Times in 0 Posts
Default

Hi All,

I made some progress about this issue:

I dismounted the front of the car to get to the big ventilator. Attached some photos.

TC, can you identify the ventilator if it's the 3 speed or the 2 speed? The only thing that connects to the fan is the box with electronics inside.

How can I check if the fan is damaged? To be honest it doesn't look good (a lot of rust) and is makes a sound when I try to spin it like some wires (or something similar) are loose around the rotor (no visibility).

Please see the photos. I didn't do the trinary test yet. I'll try to make it this evening and get back with the results. But can you tell me if it's a 2 or 3 speed so I can make the test more accurate?

Thank you!

Regards,
Alexander







Alexander MOB is offline   Reply With Quote
Old 15th August 2016, 15:26   #10
T-Cut
This is my second home
 
Rover75 and Mreg Corsa.

Join Date: Nov 2006
Location: Sumweer onat mote o'dust (Sagin)
Posts: 21,751
Thanks: 341
Thanked 3,660 Times in 2,924 Posts
Default

Quote:
Originally Posted by Alexander MOB View Post
TC, can you identify the ventilator if it's the 3 speed or the 2 speed?
Yes, it's clearly a 3-speed as indicated by the four wires feeding the motor. The brushes are probably worn away. If you can remove the motor and dismantle it, you'll know whether it's recoverable. If the commutator is in reasonably good condition, you could try fitting new brushes. There are HowTo's on this.

If not, you'll have to replace the whole shebang, preferably with a later 2-speed type. This will require the default resistor upgrade to make it reliable. You may well get everything from the forum traders or from eBay. There's usually plenty around.

TC
T-Cut 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 13:41.


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