C5 II Glow plug relay test

[sydo]

Hello everyone, my C5 II 1.6hdi won't start in cold weather. I removed the glow plugs and checked them externally. They work. The glow plugs are in good condition. Also, when I check them by plugging them into the vehicle's glow plug socket, they don't heat up. I suspect the glow plug heater relay is faulty. How can I test the glow plug relay?

[MattBLancs]

How cold are you talking? Sorry showing my ignorance as to what ambient temperature you might encounter in Turkey.

The glow plugs don't have to work very hard (e.g. unlike in an old XUD where they are essential in cold weather) on a HDi engine so I'm surprised if you are having starting issues (unless well below zero)

[mickthemaverick]

This site will give you an idea of how it works and how to test it. You need to check the fuse for the relay coil is good and that when you try the starter the relay operates. https://pinoutdiagrams.com/relay/glow-plug-relay-pinout

[sydo]

How cold are you talking? Sorry showing my ignorance as to what ambient temperature you might encounter in Turkey.

The glow plugs don't have to work very hard (e.g. unlike in an old XUD where they are essential in cold weather) on a HDi engine so I'm surprised if you are having starting issues (unless well below zero)

The city I'm in is currently around -2 or -3 degrees, but in the winter months the temperature can sometimes drop to -30 -40 degrees.

[sydo]

This site will give you an idea of how it works and how to test it. You need to check the fuse for the relay coil is good and that when you try the starter the relay operates. https://pinoutdiagrams.com/relay/glow-plug-relay-pinout

I forgot to write that the fuses were checked and all are in working order.

[MattBLancs]

How cold are you talking? Sorry showing my ignorance as to what ambient temperature you might encounter in Turkey.

The glow plugs don't have to work very hard (e.g. unlike in an old XUD where they are essential in cold weather) on a HDi engine so I'm surprised if you are having starting issues (unless well below zero)

The city I'm in is currently around -2 or -3 degrees, but in the winter months the temperature can sometimes drop to -30 -40 degrees.

Ah fair enough, glow plugs will have a job to do if it's that cold.

Just to confirm what you have already tested, have you put a multimeter to confirm if the glow plug feed comes on (would expect to see near 12 v on the terminal on top of the glow plugs) access isn't great on the 1.6 HDi with the air filter housing in the way, but perhaps rigging up a lead (with care it can't touch anything in the engine bay as it's effectively a positive connection in a land of abundant earthed metalwork!) would allow checking if the voltage appears.

[sydo]

When exactly does the glow plug engage, and at what engine and air temperatures does it activate?

[sydo]

I ordered a glow plug relay online using my car's chassis number, but the relay I received is different from the one removed from my car. My car has an 8-pin relay, while the new one that arrived is 7-pin. I'm not sure if it's compatible or if it will work.

[PaulC5]

I would check again with the supplier that they have sent the correct part.

You have 2 different part numbers as you will have noticed. Your old one is 9802424080 and the one purchased is 9645668680. Depending on what the supplier says, then the only way to see if the new one works may be to try it. Possibly a previous owner has fit the wrong one if the glow plugs have never worked whilst you have had the car or there has been an update to the part. A search shows the old part is still available https://www.ebay.co.uk/itm/333215814229 ... gLalPD_BwE

[Paul-R]

Do both of the large spade terminals have a matching electrical contact in the connecting plug? Two thoughts occur to me. 1) It's just plain wrong and has possibly never worked as a result of that. 2) The second spade terminal doesn't connect to anything and it doesn't matter because all the current is carried by the first terminal.

[cit-rotti]

Modern diesel vehicles are preheated and post-heated depending on the water temperature. This is controlled by the preheating control unit.
Only the relatively short duration of the preheating process is displayed – post-heating can only be measured – a clamp ammeter is useful for this.
You can actually hear and feel when the preheating device is switched on/off (place your hand on the glow control unit).

Each cable can be checked either with an ohmmeter (plug disconnected) or, better still, with a clamp ammeter via the connected cables. A glow plug that is still working requires up to approx. 16A – decreasing with the glow duration.

The easiest way to measure this is with the clamp ammeter via the negative terminal. This is where the total current flows (when the engine is cold), including the 4 glow plugs; i.e. the total current is 4x16A slowly decreasing + the current that flows without the glow plug system. After 2 glow processes, the current flow without the glow system is known. Then, when the ignition is switched on, an additional approx. 60A (falling) must flow. If it is only an additional 30A, 2 glow plugs are defective, etc. You can clearly hear and see when the relay switches off. The total glow time is much longer than the glow indicator shows.

An ampere measurement or ohm measurement on the individual supply lines of the glow plugs provides information about which glow plug is defective.
However, it is advisable to always replace all four glow plugs – otherwise, the entire procedure and dismantling must be repeated the next time a defect occurs.

[sydo]

I would check again with the supplier that they have sent the correct part.

You have 2 different part numbers as you will have noticed. Your old one is 9802424080 and the one purchased is 9645668680. Depending on what the supplier says, then the only way to see if the new one works may be to try it. Possibly a previous owner has fit the wrong one if the glow plugs have never worked whilst you have had the car or there has been an update to the part. A search shows the old part is still available https://www.ebay.co.uk/itm/333215814229 ... gLalPD_BwE

I received information about the new relay from a technician specializing in electronics at Peugeot Citroen. He explained that the old relay had two large pins in the middle, one positive and one negative, but the new relay only has a positive pin, and the grounding connection is made by screwing the relay body to a metal part in the vehicle, thus ensuring flawless operation. He also said that the part number has been updated, that this is the new, updated relay used in Peugeot Citroen production, and that it is released with a VIN number.

[Mihael_M]

The number 9645668680 corresponds to that Model. But at all sellers, the relay with that number has that pin 5. Maybe it can work without that pin, but I would still search with all the pins. Otherwise, the relay is difficult to check except to install it. The heaters must be on when the engine is started unless the engine is already warm. It is very difficult to check whether they are receiving voltage, since this can only be done when they are mounted, and then it is difficult to reach them with these motors. With Renault engines, it's easy because the heaters are on the front. That's why when faced with the dilemma of whether they are good or not, it is better to take them out and change them if they cost less than paying a mechanic again. Who works alone does not cost him anything, but there is a lot of work to change.
Now the main question is whether you suspect the heaters just because the car starts hard when it's cold. It doesn't have to be because of them but because of some other parts or temperature sensors. If the relay or heater is not good, then an error occurs in the diagnostics.

Sydo, what you previously wrote about the relay is correct. The new relay does not use that pin as it is ground and gets it via the screw that secures it. In that case, you should pay attention that the contact where it is located is clean and free of rust.

[Paul-R]

Do you know I wondered whether the missing terminal was an earth and that the return was now made through the metallic body but I discounted it because I couldn't see why the earth return on the original had to go through such a large terminal. It would surely have had very little current flowing through it as it would have only been the return flow from the activating coil.

Just goes to show that you can overthink things and talk yourself out of the correct answer!

[sydo]

The number 9645668680 corresponds to that Model. But at all sellers, the relay with that number has that pin 5. Maybe it can work without that pin, but I would still search with all the pins. Otherwise, the relay is difficult to check except to install it. The heaters must be on when the engine is started unless the engine is already warm. It is very difficult to check whether they are receiving voltage, since this can only be done when they are mounted, and then it is difficult to reach them with these motors. With Renault engines, it's easy because the heaters are on the front. That's why when faced with the dilemma of whether they are good or not, it is better to take them out and change them if they cost less than paying a mechanic again. Who works alone does not cost him anything, but there is a lot of work to change.
Now the main question is whether you suspect the heaters just because the car starts hard when it's cold. It doesn't have to be because of them but because of some other parts or temperature sensors. If the relay or heater is not good, then an error occurs in the diagnostics.

Sydo, what you previously wrote about the relay is correct. The new relay does not use that pin as it is ground and gets it via the screw that secures it. In that case, you should pay attention that the contact where it is located is clean and free of rust.

The instrument panel shows the engine temperature as running; if the temperature sensor were faulty, shouldn't the instrument panel not show the temperature?