Overvolt Relay
#1
Overvolt Relay
Well,one of the issues I started to try and work out on my '88 VDP is solving the ABS Failure warning light. I've already removed the wheels and cleaned all four ABS sensors with Brake Cleaner. I'm still getting the ABS Failure Warning so my next step would be to either try and find a new Overvolt Relay or possibly fix one of my existing ones. I have one on the car and a spare but neither seem to fix the problem. Does anyone know of a way to test the Overvolt Relay to see if it's working properly. I understand there's an internal fuse that tends to go bad on these. What are my options?
#2
#3
#4
#5
Join Date: Feb 2014
Location: Crossroads of America
Posts: 19,677
Received 13,463 Likes
on
6,635 Posts
I assume you can open the relay since Bob mentioned cold solder joints on the circuit board.
Another test you can perform at the ABS Module electrical connector is to measure the resistance of each wheel speed sensor and its wiring harness. Based on an X100 I recently measured, I would expect DC resistance to be be in the range of 1,000 ohms to around 2,000 ohms. The Electrical Guide shows which pins in the connector apply to each speed sensor. If you find the resistance of one of the circuits is much lower than the others, it is probably shorted. If you find one with infinite resistance, the sensor is dead, a harness wire is broken, or there's a problem with the electrical connector.
If I recall correctly, another relatively common issue is either poor solder joints in, or water ingress into, the ABS Module.
Cheers,
Don
Last edited by Don B; 02-24-2017 at 06:54 PM.
#6
The fuse is a GLASS fuse with a white foam around the metal link so the fuse-link is NOT visible. If you do not know how to test continuity of a fuse, then the diagnosis is best left to someone familiar with 'electrics'.
Soldering is not difficult but requires a soldering iron and solder.
bob
Soldering is not difficult but requires a soldering iron and solder.
bob
#7
I managed to test my Overvolt Relays today. One tested with good continuity and the other one had nothing. I managed to open up the faulty one to see what I'm assuming was a bad fuse. Although I didn't see an actual fuse I did see where there was a gap of what had looked like a strand of wire going across two terminals. I'll resolder a piece of copper wire strand across the gap so I can use this as a future spare. I've already cleaned all four wheel sensors and know I've got a good Overvolt relay installed so my next step will be checking for proper resistance of the wheel sensors as Don suggested.
Trending Topics
#8
#9
Join Date: Feb 2014
Location: Crossroads of America
Posts: 19,677
Received 13,463 Likes
on
6,635 Posts
EDIT: Another thought is that you could use the wire from a small glass-envelop buss fuse by applying tape to the glass to keep small shards from flying everywhere, carefully breaking the glass and extracting the wire. Depending on how much length of the original wire will fit across the terminals in the relay, the actual breaking current may be altered, so you may have to estimate the change in order to choose a fuse from which to extract the wire.
EDIT: Somehow I didn't see Bob's post #6 about the fuse in the relay being a glass-envelope fuse. Guess it would be best to just try to find the correct size and rating?
Cheers,
Don
Last edited by Don B; 02-25-2017 at 06:44 PM.
#10
Join Date: Feb 2014
Location: Crossroads of America
Posts: 19,677
Received 13,463 Likes
on
6,635 Posts
The following users liked this post:
93SB (02-25-2017)
#11
I believe the original fuse is rated at 8 amps. It looks as if it may have been replaced beforehand but I can't verify that as I've never had to deal with an Overvolt Relay before. It looks as if someone just had a thin piece of silver stranded wire going across the gap,which doesn't look to be more than about 3/4" across. If someone has a pick of what an original fuse link might have looked like it may be helpful. I did think of using a strand from a glass automotive fuse but not sure if it would withstand being soldered without breaking the gap and melting.
#12
Pics of overvoltage relay
95 leaper
Don has the professional schematic....mine is a sketch...both the same
please see my pics in my album titled OVERVOLTAGE RELAY.
I have an 89 XJ ...Same as your 88
Hope it helps you. its an 8 amp fuse.
I rebuilt my relay with a new TVS/Zener Diode. and bulked up the solder trace some in places where it was corroded away.
The ABS fault will go away the next time you start the car and there are no faults after the Initial Test when you get above 3 mph. (you will hear it)
My ABS fault was the diode in the OV Relay.
Don has the professional schematic....mine is a sketch...both the same
please see my pics in my album titled OVERVOLTAGE RELAY.
I have an 89 XJ ...Same as your 88
Hope it helps you. its an 8 amp fuse.
I rebuilt my relay with a new TVS/Zener Diode. and bulked up the solder trace some in places where it was corroded away.
The ABS fault will go away the next time you start the car and there are no faults after the Initial Test when you get above 3 mph. (you will hear it)
My ABS fault was the diode in the OV Relay.
The following users liked this post:
Don B (03-01-2017)
#13
I managed to use a good spare that I had laying around but plan on fixing the damaged one. Now,as for the ABS fault,here is my situation. First,I cleared all faults off the VCM to start from scratch. When I first start the car I get an ABS fault showing but it then goes away after about ten seconds. But if I shut the car off,wait about 10-15 seconds and turn the key to the "on" position to read the codes,there is an ABS fault code appearing but once the car is started and runs again,it disappears. Is this just the computer doing an ABS test mode?
#14
95 leaper
Yes...that is the INITIAL TEST of the system ( call it the" non -moving test")
then ...you start down the road and the system check again , this time it is testing the dynamic portion (SENSORS) of the ABS. if all is well no fault.
the system periodically tests itself while driving also.
this will happen every time you start and drive the car.
Yes...that is the INITIAL TEST of the system ( call it the" non -moving test")
then ...you start down the road and the system check again , this time it is testing the dynamic portion (SENSORS) of the ABS. if all is well no fault.
the system periodically tests itself while driving also.
this will happen every time you start and drive the car.
The following users liked this post:
Don B (03-01-2017)
#16
Join Date: Feb 2014
Location: Crossroads of America
Posts: 19,677
Received 13,463 Likes
on
6,635 Posts
Hi Ordinaryboy1986,
Welcome to the Jaguar Forums! It's great to have you with us.
The low brake pressure light at startup is typical of XJ40s. It can take the pump up to 30 seconds or so to pressurize the hydraulic brake boost system, especially if the accumulator is no longer holding pressure as well as it should.
I don't think the missing overvoltage relay is related to the warning lamp, but it won't hurt to replace the relay.
Please visit the New Member Area - Intro a MUST and post a required introduction so we can learn something about you and your Jaguar and give you a proper welcome.
Cheers,
Don
Last edited by Don B; 06-18-2018 at 08:57 PM.
The following users liked this post:
93SB (06-22-2018)