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Okay here comes my project on a Volvo S70.

The car can be driven but still has a few things to inspect.

Abs is on and I would need your help to turn off the light

Most likely why the brakes feel sluggish, uses a vacuum pump from volvo s80 with associated pressure valve.

Any tips?

I think the abs is not satisfied due to the lack of the petrol engine, have you got any tips on how I can get the abs to work?

Markusvolvo wrote: ↑Thu Jul 17, 2025 7:19 pm 8461-f4764b5de9cee2fb16c69b16a34842a4.jpg

That is a UP28 which is a supporting pump and not powerful enough to be used as a stand alone pump.
See also my blog https://www.evcreate.com/vacuum-pump-power-brakes/
A UP30 is the smallest one suitable as stand alone (but noisy).
If you want vacuum. I'd suggest to use an early Tesla one (also found in some Fords).

... but that does not solve your ABS issue.

Ah! I almost understood that when I ran the pump yesterday without any valve that regulates the pressure, so the pump was running at full speed all the time, still slow to brake. Many thanks for the help Lars!

I'm going to measure the entire abs system this Saturday, all sensors and cables to them, if there's nothing wrong there then I'll have to remove the abs box and see if any soldering has come loose, apparently a common problem on these

Markusvolvo wrote: ↑Fri Jul 18, 2025 5:32 am Ah! I almost understood that when I ran the pump yesterday without any valve that regulates the pressure, so the pump was running at full speed all the time, still slow to brake. Many thanks for the help Lars!

I'm going to measure the entire abs system this Saturday, all sensors and cables to them, if there's nothing wrong there then I'll have to remove the abs box and see if any soldering has come loose, apparently a common problem on these

I use either UP32 or the UP50 pumps. They have much greater suction volume and/or motor power.
https://oneclickwarehouse.net/product/h ... Ra_hE9miwr
https://citini.com/product/hella-up50-vacuum-pump/

For switch i simply find Volvo XC90 vacuum switch which is all allong intended and setup for providing for correct brake assist. It is OEM part!
Volvo XC90 switch P/N 30645383
https://leafdriveblog.wordpress.com/202 ... um-switch/

Markusvolvo wrote: ↑Thu Jul 17, 2025 7:26 pm I think the abs is not satisfied due to the lack of the petrol engine, have you got any tips on how I can get the abs to work?

ABS needs to see correct rate of change on wheel sensors together with some RPM signal from the engine.
Also when there is any error on the ABS you cant clear it stationary. Computer needs to observe all wheels spinning to clear the light. You should provide engine running state and then drive a short distance.

You can provide either dry idle signal to ECM directly on the RPM sensor...
https://evmeganetech.wordpress.com/2025 ... indicator/

Or provide clean CAN bus report that ECM is sending to VCU inside cabin.
Volvo being quite advanced car electronicaly had CAN bus very early.
This site may help...
https://s80ev.blogspot.com/2017/10/0x16 ... bit-6.html

What great knowledge you guys have! It almost brings tears to my eyes Many thanks! Now I have to hunt for a new pump so I get the right type of brake assist. Many thanks again!
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arber333 wrote: ↑Fri Jul 18, 2025 6:58 am ABS needs to see correct rate of change on wheel sensors together with some RPM signal from the engine.
Also when there is any error on the ABS you cant clear it stationary. Computer needs to observe all wheels spinning to clear the light. You should provide engine running state and then drive a short distance.

You can provide either dry idle signal to ECM directly on the RPM sensor...
https://evmeganetech.wordpress.com/2025 ... indicator/

Or provide clean CAN bus report that ECM is sending to VCU inside cabin.
Volvo being quite advanced car electronicaly had CAN bus very early.
This site may help...
https://s80ev.blogspot.com/2017/10/0x16 ... bit-6.html

Tried sending PWM to cluster, but it had no effect, makes the needle move but this only with a fixed PWM signal, saw your page where you send signal with 58/2, where do you send your signal? Do you send it to the motor control or?

Managed to find the fault, it was an abs sensor that kept failing, after I replaced it everything worked after a test drive. Many thanks to everyone involved in this problem

this is what I am using but did not drive the car much so far so I can tell how good or bad it is.

https://www.amazon.com/dp/B0BL1HWHW9?re ... in_title_4

Markusvolvo wrote: ↑Fri Jul 18, 2025 12:42 pm Tried sending PWM to cluster, but it had no effect, makes the needle move but this only with a fixed PWM signal, saw your page where you send signal with 58/2, where do you send your signal? Do you send it to the motor control or?

About that... Megane flywheel is setup for 60-2-2 signal. So there is 57 teeth with one long gap worth 2 teeth and 2 teeth together. This is so ECM will know when a full revolution is performed. You need to count flywheel teeth and then program your VCU so it will output that signal at about 1000rpm rate.

Like i said in my blog i signal pwm through 1uf plastic cap. This has an effect to drop the voltage below 0V line and ECM will know to read this signal. I connect this to one wire of RPM sensor output and leave the other unconnected because it is connected to GND somewhere, which would pull my signal down and make it ineffective. Hope this helps. If you have questions do ask...

arber333 wrote: ↑Fri Jul 18, 2025 7:27 pm About that... Megane flywheel is setup for 60-2-2 signal. So there is 57 teeth with one long gap worth 2 teeth and 2 teeth together. This is so ECM will know when a full revolution is performed. You need to count flywheel teeth and then program your VCU so it will output that signal at about 1000rpm rate.

Like i said in my blog i signal pwm through 1uf plastic cap. This has an effect to drop the voltage below 0V line and ECM will know to read this signal. I connect this to one wire of RPM sensor output and leave the other unconnected because it is connected to GND somewhere, which would pull my signal down and make it ineffective. Hope this helps. If you have questions do ask...

Troubleshooted the abs system and for some mysterious reason an abs sensor had given up, when I changed to a new one and test drove to 30-50kmh the light went out by itself, this means that it doesn't need any RPM signal from the engine at all, so incredibly surprising!

I really appreciate you sharing your knowledge with how you did it with your Renault, when I build a more modern car next time I will contact you again Many thanks!

larsrengersen wrote: ↑Thu Jul 17, 2025 10:50 pm That is a UP28 which is a supporting pump and not powerful enough to be used as a stand alone pump.
See also my blog https://www.evcreate.com/vacuum-pump-power-brakes/
A UP30 is the smallest one suitable as stand alone (but noisy).
If you want vacuum. I'd suggest to use an early Tesla one (also found in some Fords).

... but that does not solve your ABS issue.

I saw you had a Tesla pump on your website, I'd love to buy it! Is it as easy to connect as my current pump?

The car is finished!

Just light maintenance now, but I've driven the car every day since it was inspected on 2026-01-16.

So great that everything works even at -35C in Sweden.