Auto Service World
Feature   July 1, 2000   by CARS Magazine

SSGM Tech Tips (July 01, 2000)

Don't forget the front end when dye testing A/CUltraviolet sensitive dyes are a great way to spot refrigerant leaks in air conditioning systems, but don't limit your inspection to the obvious under ho...

Don’t forget the front end when dye testing A/C

Ultraviolet sensitive dyes are a great way to spot refrigerant leaks in air conditioning systems, but don’t limit your inspection to the obvious under hood area. The evaporator is exposed to rocks and road debris, and can be distorted or cracked by impact with everything from curbs to snow banks. Damage to air dams or fascias are a hint, but in every case, get down on your hands and knees and check the face of the evaporator thoroughly, even if you’ve “found” a leak elsewhere. Poorly executed front-end bodywork can cause several problems ranging from evaporator tubes pierced by screws to distorted or missing brackets. Add the recommended amount of dye and no more; excessive quantities won’t help find the leak any faster. And do wear those amber glasses. They dramatically improve the visibility of low-level seepage.

Consider adding a ground

Suspect an intermittent or broken ground in the electrical system? Troubleshooting bad grounds, especially where they’re remote from the current drawing device, can be time-consuming and frustrating. It may be faster to simply solder in a new ground “pigtail” with an attached ring terminal, and ground to the chassis with a self-tapping screw. Automakers don’t like them, but #2 Robertson screws are ideal since they stay on a screwdriver bit, leaving your hands free to drive the screw accurately. Use type “B” screws wherever there is a risk of a sharp point piercing wiring behind the panel you’re drilling, and choose plated screws for corrosion protection. Apply a rust preventative to the back side of the piercing, and don’t be afraid to use silicone dielectric compound, especially if the area is exposed to moisture. Naturally, any place near the fuel system is a no-go, and screwing into blind panels isn’t a good idea unless you’re sure about what’s inside.

Anti-seize do’s…. and don’ts

Anti-seize compounds are great for keeping parts from “freezing”, and do make later disassembly easier for repeat customers, but they shouldn’t be used everywhere. Most are oil-based, so keep the product away from plastics and rubber of any kind, and most contain lead, which is dangerous to ingest. Wash your hands thoroughly after exposure, and definitely before eating, drinking, or smoking. And possibly the most poplar application for anti-seize compounds is no longer a “no-brainer”: spark plugs. Some manufacturers now plate the threads of spark plugs with a sacrificial coating to prevent seizure, and recommend dry installation. Check the packaging and ask your jobber, especially for vehicles with extended plug change intervals.

Turn signal weirdness

Strange or erratic performance from lighting circuits can have some unusual causes, most of which can be checked out quickly and easily. Dual-filament bulbs can fail with one filament shorting across the other, creating unusual system loads and performance. Many vehicle owners know that pulling bulbs is fast and easy, and won’t hesitate to replace with anything they can wedge into the socket. The same goes for the flasher unit. They’re not as interchangeable as most motorists think, and an incorrect do-it-yourself flasher installation can cause trouble. The same is true of fuses, where owners will generally use anything handy to get the system working. Missing fuse panel covers are a sure warning sign. Don’t count on the owner telling you about that roadside “quick fix” last month, either. Ask about recent bulb or flasher replacements, and start the inspection there. And if you sell halogen replacements over the counter, remind the customer about the ‘no fingerprint” rule for installation.

Print this page


Have your say:

Your email address will not be published. Required fields are marked *