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Re: ABS Pump Fuse Blowing Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Wed, 17 Dec 2008 07:06:59
In Reply to: ABS Pump Fuse Blowing, Ben H, Tue, 16 Dec 2008 22:58:55 Members do not see ads below this line. - Help Keep This Site Online - Signup |
A short circuit won't cause a fuse to blow after a few days - it'll blow immediately.
The most likely reasons for the fuse to blow is a tired ABS pump or an overworked ABS pump. If the pump is just pulling too much current, it'll keep that fuse up at high current long enough that it finally melts.
The other possibility is that the pump is running too much. The pump should be running intermittently. If it is running all the time, it gets hot, the load changes, and the fuse can blow.
Test 1 - after the car has been sitting - overnight is best - check the level of the brake fluid in the reservoir. It should be well ABOVE the FULL line. Note that the full line is well down the reservoir.
Start the car. You should hear the ABS pump running. The fluid level should drop. After about 20-60 seconds, the pump should stop running, and the level should be down at the FULL line.
Test 2 - Once the pump has stopped, get back in the car, and with the engine running, stomp the brake - hit it fast and hard - press and release. Count how many stomps it takes before the ABS AND Brake Fluid lights come on. More than 12 is good; 5-11 is a weak accumulator; less than 5 is a bad accumulator.
OK, say you start the car, the brake fluid level drops, and even after it gets near the FULL line, the pump doesn't shut off. The pump just keeps running. The most likely problem is a bad pressure switch. The switch assembly is screwed into the ABS master cylinder. Or a pressure switch wiring problem, or the ABS pump relay contacts are stuck together. The last possibility is a bad valve in the ABS body, so it can't hold pressure. That requires $$, so let's hope it isn't. If the pump is always running, it's a race to see if the fuse blows before the pump overheats.
OK, say the pump does shut off, but it fails the stomp test. Time for a new accumulator - easy and not that expensive (~$120, using the Buick part). The system doesn't hold pressure, so the ABS pump has to run most of the time.
The last possibility is a tired ABS pump that has lots of friction, and is pulling too much current. No happy solution to that.
email me (click on my name above), and I can send you schematics for a '88 ABS system.
posted by 192.249....
, Wed, 17 Dec 2008 07:06:59 <-- Viewing This Message
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