Heater Help Please?, Blocked heater matrix or closed valve?

Hi. I've a series 2 V6 Exclusive Estate with aircon (climate control?). Since I first bought it, the heater has been very poor and now (Winter closing in), it's worse. Plenty of airflow, but tepid to lukewarm at best. I've checked the water hoses to the heater, with both disconected from the engine block and the ignition on; 30 (hotest setting) selected on the temperature control in the car but the engine not running, using a funnel in the top hose there's virtualy no water flow; just a dribble like a leaky tap out of the bottom hose. Is this a blocked matrix, or is there a valve (maybe stuck in the `closed' position) somewhere on the heater matrix itself? Before doing this, all hoses connected and the engine at running temperature, the heater hoses are warm but not hot.

There's an air temperature sensor with a small fan hidden in the cabin light housing. The fan works, and there's a low voltage (about 3 volts?) across the temperature sensor. With the sensor unit unplugged (disconnects sensor and fan) and also with the sensor unit plugged in but the sensor itsef shorted out, there's no difference to air temperature from the heater.

Has anybody any idea what I can try to get the heater working? Regards, Jim.

Jim,

As far as I know the heater matrix should have engine-temperature coolant circulating through it all the time - it's just the positioning of a servo-operated flap in the heater unit that dictates how much air is directed across it dependent upon the control unit settings or by sensing the temp inside the cabin (if on 'auto').

From your symptoms of very little flow through the matrix, I'd suggest you try back-flushing it (if you haven't already?).

When was the anti-freeze last changed? At least every 5 years is a must, even with long-life coolant. It's an achilles heel on Citoens in general!

Hope your matrix isn't completely blocked - it's a bit of a pig to replace.

I have had problems with the servo motor valve on previous xantias and peugeots - cured 100% by removing the servo motor drive mechanism and going over every joint on the circuit board with a soldering iron - they seem very susceptible to dry joints.

This post has been edited by wirdy on January 21, 2007 05:38 pm

Hi Combwork.

I think you might be 'lucky' in just having a sludged up matrix from your description of the flow situation. As Wirdy suggests, I would be looking to flush it ---- umpteen times, in both directions if you have the time. One thing I absolutely wouldn't use is any of the 'Radflush' type things. I have in the past, closely followed by water pump failure. I'm very suspicious of it. After that, I'd drain some coolant and make the anti freeze up to about 50%, which should keep things flowing. Don't forget to bleed the system as appropriate. Good luck.

Mike.

Hi Weirdy,

Many thanks, I was worried that there might be a valve in the matrix somewhere; didn't want to damage anything by trying to force high pressure water through a closed valve. One thought; (I'm just thinking out loud). Is the matrix copper? If it is, and there are no other metals (apart from lead solder) involved, with both hoses disconected from the block it should be safe to put dilute (25%) Sulphuric acid in it. This stuff disolves most things, but not copper.

Just a thought. If I'm wrong, maybe the risk of dumping a litre of Sulphuric acid behind the dashboard isn't such a good idea.................. Jim.

Hello Mike,

I have the time; as I said to Weirdy I'm just trying to figure out a chemical that would speed things up. I use Sulphuric acid in my workshop and I know it won't disolve copper or most plastics. What I was most concerned about was whether there was a valve in the system that might be locked closed. If I did use any chemicals, I'd make sure they were well flushed out (acid with 10% Soda solution). I've an old 24 volt pond pump that I could rig on a closed circuit pumping various solutions through the matrix.

One query; of the two pipes that come out of the block, which is flow and which return?

Many Thanks gor your help,

Jim.

The matrix isn't a bad job to do - usually 30-40 mins - but you'll need to drop the steering column off the dash and undo it's joint to the lower steering knuckle.

I'd try simply feeding normal hose pipe water pressure through until it comes out the other end clear. The matrix itself is the lowest point in the cooling circuit so any debris/vrap will settle there eventually. It's not that robust being lightweight ally material.

In the past, I've seen a dissected Cx matrix where there was what looked like steel spiral (just like a spiral staircase) running inside the main connecting pipes between both end caps. Basically, and it will be no surprise here, they actually degraded down to a rusty pulp and blocked the feed through the matrix causing a leak. Not sure if it's the same on the Xm one but I should cut up an old one I've still got lying around to see. It's not uncommon for an Xm to need a new matrix once a year!!

Andrew

Hi combwork,

As stated above there's no valve, it should be full flow all of the time. Variations in the amount of heating is achieved by directing different amounts of air over the matrix and the balance past it. What you get in the cabin is the blend of the two.

I don't think the matrix is copper. I have a fancy the tubes are aluminium. The end tanks are plastic. I'm not sure I'd be tempted by the sulphuric in the sense that I'm not sure that the sludge composition would be attacked by the acid.

As Andrew said the matrix isn't that bad. With the steering column pushed to one side its actually quite easy and there's only 4 bolts to the steering column. I replaced mine about a month ago and it took me about an hour including drain down into a bucket to keep the glycol. The bit that took the longest was to get the new matrix into the housing from about half way in. There's an internal flange in the heater box. If you don't get the matrix perfectly aligned on entry the fins on the matrix snag on the flange. It took me 15minutes to wrestle with the matrix on the way in. I've done one before and I must have been lucky that time because it just slid right in.

Oddly enough about 6 weeks ago I had no heat at all. I checked the flap and it was pointing in the cold direction. I took the carpeted card of the passenger side of the tunnel and then removed the servo motor. I exercised the motor by moving the temperature control knob and the motor worked OK. I exercised the flap and it moved OK. I reassembled it and it worked OK. Never did find out what the problem was but its worked fine ever since.

If you want to bring it down one saturday morning I can check the flap and if you get a new matrix I'll give you a hand to fit it.

Cheers

noz

Thanks Noz,

That's a great offer which I'll be glad to take you up on. Even if I get the heater working ok, I'd appreciate your thoughts on future work on the car. Thinking about it, sulphuric acid is certainly a bad idea. Maybe if I was 100% sure it was copper it could be worthwhile, but alluminium and plastic? No no no; no acid............

Best Regards,

Jim.

Some pics with descriptions. Looks like a mostly aluminium core.

http://craigdeb.com/xm/XM%20Heater%20Core.htm

These pics will move one day in the next few months but I will probably put a redirect there anyway.

I congratulate you on your photos - very instructive. I was instructed otherwise than the method used by you; I was told how some garages do it to cut down on the time required, as follows:-
Access the heater matrix as you show, then, without touching anything relating to taking the steering column out of the way, diconnect the heater pipes and drain the water as shown in the photos then pull the matrix out. I know you have to bend it slightly to do so,, but so what? It's scrap anyway! Then cut out a triangular section of the heater box (with a Stanley knife) on the side facing you. Cut from the top RH corner diagonally downwards to a point roughly ! 1/2 ins (35 mm) along from the bottom RH corner. With this cut away, the matrix will slide in without damage. When it is connected to the heater pipes, the cut-away section of the matrix box can be re-fitted in place with heavy duty Duck Tape ready for the next replacement in 2-3 years time. I have used this method succesfully several times and found it a great time-saver.

This method of cutting away the housing is described in the Haynes Manual with a helpful photo.

John

GOOD NEWS!!!!!!!!!

After vigerous flushing using a manual plunger type pump (about 1 litre capacity `suck and blow') followed by hot water from a hose pipe in both directions, the matrix is clear and the heater works fine. Amoungst the usual brown slurry, I got about a tablespoon of SAND out of it. How the **** can a heater matrix get sand in it?

The car runs well, but fuel consumption has been better. With all this mucking about plus a year standing idle, could the electronics, ignition timing, mixture strength etc have gone to some kind of basic mode? Is there any way of checking this?

Best Regards,

Jim.

Hi Combwork.

Congrats on the heater. Nice to get a result without too much aggro ! Don't know about the V6 models, but after a year standing around with any version, I would be looking to check that none of the brakes were sticking. Even a small amount of binding will soon knock 1 or 2 mpg off. After a run, just feel around the centre of the wheel rim, near the studs. Any perceptible heat and you need to investigate the relevant caliper. If you happen to have the rear jacked up, then simply try spinning the wheel. The rears should spin with virtually no resistance.

Mike.

Hi Combwork

When a V6 is running in limp mode it is so lithargic that you can tell straight away as there is virtually no acceleration except downhill.

Regards

XMexc

Hi XMexc,

Thanks for that; I don't think thats a problem really. There's an uphill straight on the way into Kirriemuir. Starting at 40ish, flatening the accelerator kicks the auto box down to second and the car goes like a rocket. Hits 80 plus before the grin is replaced with fear and I have to back off. Not bad for an old git in a big Estate car.